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Reflection #6: Sea Level Change Through the Last Glacial Cycle (2004)
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 Reflection #6: Sea Level Change Through the Last Glacial Cycle (2004) |
topic started 1/10/04; 11:09:50 AM
last post 5/6/05; 5:38:03 PM |
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 hamannmm@m... - Re: Reflection #6: Sea Level Change Through the Last Glacial Cycle (2004) 
2/19/04; 1:14:41 PM (reads: 41785, responses:
0) |
What was done/ what were the methods?
Kurt Lambeck and John Chappell researched the cause and effect of sea level change through the last glacial cycle. They identified the cause as the cyclic growth and decay of ice sheets and the effects as complex spatial and temporal patterns. Their observations were done on a number of different scales for time, location, and intensity of shifting; example- location was divided into global, regional, and local. Lambeck and Chappell presented their findings in a number of categories: observational evidence, glacial isostasy, ice volumes through the last glacial cycle, mantle viscosity, and shoreline reconstruction. Basically, the purpose of the study was to take into consideration a variety of geologic, atmospheric, and oceanic properties around the world and develop a model that closely resembles what has happened in the past and what may happen in the future.
-True Source of Data:
Lambeck and Chappell had a plethora of true data sources. They used glacial signaling, ice loads, plate tectonic information, peats, sediments, radiocarbon dating of materials deposited near the ocean-land transition zones, deltaic sediments, in situ tree roots, the age-depth relationship of fossil corals and isotopes. This information was presented in a number of figures. They also used an equation that related the glacio-hydro-isostatic contributions to sea level. It is important to remember that this is more of a synthesis article and the majority of the data it contains came from a source other than Lambeck and Chappell. No matter what is the source of the data, "most of the available sea level data is for the period after the last deglaciation, because earlier records were mostly destroyed by rising sea levels at he onset of deglaciation or by advancing ice sheets during the lead-up to maximum glaciation."
What was learned/ were the results?
1) Earth-response if depth and spatially variable.
2) Global sea level fluctuations are primarily a result of plate tectonics.
3) Regional and local sea level fluctuations are a result of uplift and subsidence of the coastal zone or climate change.
4) Terrestrial materials deform nonlinearly when exposed to stress, but linear viscoelastic models appear to be adequate for describing observed glacial rebound phenomena.
What did I get out of this article?
Some great information as well as some interesting facts like the primary cause of planetary deformation is water load. That coral is super cool because it can be used for both radiocarbon and uranium-series methods and "it provides the basis for calibrating the radiocarbon time scale for the interval that is beyond the capabilities of varve and tree-ring chronologies."
How did/will this article change my thinking?
That most of the subjects that this class is presenting are immense in proportion to what scientists are able to study. Therefore, they must make many assumptions when predicting both the past and the future. I am one that likes no ambiguity in my results so this is a tough concept for me to absorb and adhere to. If done, however, it can lead to new discoveries or generally accepted theorems. Like Mendel didn't know why he got the ratios he did, but later other cytologists discovered chromosomes and then they applied the chromosomal theory to Mendel's work to explain their own findings.
So assumptions are okay... yep that is what this article did for my thinking!
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nagyrc@m... - Re: Reflection #6: Sea Level Change Through the Last Glacial Cycle (2004)
2/23/04; 11:58:15 PM (reads: 41665, responses:
0) |
These authors used many sources to examine sea level changes throughout history as they relate to glacial events, properties of the physical composition of the earth's layers, and changes in coastal structure. They compiled research from many others including methods/studies of: peats, varves, corals, isotopes, sediments, and tree-rings. They used equations to model sea level changes with respect to time, position, ice volume, and water depth.
They said that changes in sea level are due primarily with changes in the ocean basin geometry due to plate techtonic activity. The changes in glaciation relates directly to changes in ocean basin geometry. They found "regular" fluctuations of sea level change that coincide with the Heinrich events that we read about in a previous article. They also learned that the viscosity of the earth is depth dependent and spatially variable. The average viscosity for the lower mantle is much greater than that of the upper mantle. Additionally, their results confirmed that the viscosity of the oceanic mantle is less than the viscosity of the continental mantle.
I think that these authors took an interesting approach to the commonly studied sea level changes. Their results indicate that the geology of the earth is a very important factor to consider when studying past changes in sea level. They then used their findings to relate to other effects such as glacial changes. I think that their model of shoreline reconstruction (Fig. 4) was helpful to see how they can apply their findings for future predictions. Additionally, I thought that they supported their emphasis on spatial variation (with Fig. 2) very well to show that the changes are often not global, but rather vary regionally.
I feel that this article re-emphasizes what many of the articles already have...All attempts to reconstruct past climates are incomplete and at best, assumptions to be modified by further studies. They admitted that much of their data was not hard evidence, but rather predictions based on the evidence that they do have. With increasing technology, such as modeling programs, perhaps the results will get more accurate in the future.
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pudgemobile@m... - Re: Reflection #6: Sea Level Change Through the Last Glacial Cycle (2004)
2/24/04; 12:14:01 AM (reads: 41834, responses:
0) |
In this review, Kurt Lambeck and John Chappel present information on historical changes of sea level in different areas of the world. The writers were mostly interested in changes after the last glacial maximum due to the destruction of data and evidences by the ice sheets. They first document evidences that can be observed, like emerged coral reefs, submerged tree stumps or deposited materials that are out of place. The writers use and show mathematical formulas and reference models in an attempt to figure how ice and water isostacy influence the rise and fall of sea level in different areas. They generalize sea level patterns into groups by their location relative to major ice sheets. Generally, there are three areas in which sea levels are following patterns due to isostacy. These are:
- Areas directly under the ice sheet. These areas are experiencing a general lowering of sea level due to the mantle/lithosphere rebounding back to its origional position and lifting the land faster than sea level rises due to melting ice.
- Areas near the edges of the great ice sheets. These areas, at first, undergo a rapid rise in sea level. This is due to the movement of the mantel/ lithosphere that has buldged into these areas because of the weight of the ice, moving back to its origional position. The material continues to move back but at a slower rate, so sea level continues to rise slowly, even after all ice has melted.
- Areas farther from the ice sheet. At these areas water isostacy caused by melting glaciers is the main deformation contributor. This causes sea levels to slowly lower
The writers then explain how the viscosity and density of the mantel is important when figuring glacial displacement and land rebound. Due to problems with understanding how the mantel flows, they site models that conform to data on a regional, not a global basis
Our authors finish with a detailed description of the changes in sea level of the Bass Straight.
What I thought: This article provides very complex analysis of rising and lowering of sea level. The equations the writers provide are really too complicated for me to comprehend, but the results are very interesting. This review improved the way I think about sea level changes, it is no longer as simple as melting ice = higher water, but a complex situation that is dependent upon techtonics, density, viscosity, and isostacy.
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greenerr@m... - Re: Reflection #6: Sea Level Change Through the Last Glacial
2/24/04; 10:58:02 PM (reads: 41767, responses:
0) |
The article's authors decided to look at a combination of geological
events in an attempt to understand the increase in sea level. The
record of glaciers was used as a foundation for comparrison which makes
sense concidering that the fundamental basis regarding sea level
would be for a source of water. However, the interesting part of the
article was the other events that they compared to. For example, the
notion of the viscosity for the lower mantle and the upper mantle
helped play a major role in understanding how changes in sea level
occured with stress. It would seem that the graphs presented
showed an interesting trend that I feel didn't get fully explain.
Understanding the correlation might explain the sea level fluctuations.
I'm not sure I fully understood some of the concepts that were
presented due to the fact I have little experience with the technical
terminology but regardless of that I thought that looking at a much
bigger picture helps generate a much more informental explaination.
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murphyj4@m... - Re: Reflection #6: Sea Level Change Through the Last Glacial Cycle (2004)
2/25/04; 10:26:10 PM (reads: 41752, responses:
0) |
| In this article the authors attempted to explain changes in sea level as related to glacier cycles. They note that it is not simply as strait forward ice melting and ocean level rising. Lambeck and Chappell state that these changes follow a spatial and temporal patten that can be linked to changes in the ice. I took this to mean that water levels may rise in one area, while lower in another and that Lambeck and Chappell were trying to link these changes to glacial patterns.
Although the article took some time to work through and I'm still not sure I could grasp all of what they were attempting to explain, I found the concept of glacial Isostasy very interesting. I had no idea that water and ice levels had effects like that or could be measured with the methods described. It made me stop and realize that everything on this planet is pressing on something else in someway or another.
At times these articles are a bit daunting but they are adding to the puzzle.
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miller43@m... - Re: Reflection #6: Sea Level Change Through the Last Glacial Cycle (2004)
2/25/04; 10:41:05 PM (reads: 41726, responses:
0) |
In analyzing the history behind sea level fluctuations, methods such as observations of coral reef fossils, submerged tree stumps, laminations, and taking carbon dating samples of coral atolls were used as references to site when and how sea-level fluctuations occurred. Tectonic uplifting, glaciation, and deglaciation are also cited as another source of sea-level changes. Lambeck and Chapell noted how glacial load on a surface caused it to rebound upward once the ice melted and caused a rise in that surface known as a type of glacio-hydro-isostatic contribution.
What was learned was that about 16,000 years ago, glacial melting was noted and continued until about 7,000 years ago when sea levels appeared to top off and stay approximately as they are today. During this time, there was a short interval where sea levels appeared to level off. Prior to 16,000 years ago, random fluctuations of sea levels appear to coincide with Heinrich ice-rafting events. Although glacial loads can be noted the exact locations and extent of these loads cannot accurately be inferred from the available data. Geophysical analysis of viscoelastic mantle vs. elastic lithosphere help describe, to some degree, the extent of the overlying load. Representative mantle conditions must be taken into account when trying to make accurate observations regarding specific regions and ice volumes. Sea levels may have fluctuated to the extent that vast stretches of land, such as one connecting Australia and Tasmania, could have been exposed when glaciation was occuring and thus provided a means for early man to reach the separate country. It is believed that this land bridge could have been exposed for nearly 30,000 years and strongly correlates with dates when the first evidence of humans on Tasmania occurred.
This article expressed some creative ways in which researchers have analysed unique factors to make predictions on the duration and extent of glacial patterns in relation to sea levels. It mentioned the degree to which these factors can be taken as well. It proposed that significant changes in sea level could have altered land features so much as to form land bridges between landmasses.
I was very interested to hear that glacial activity could have been significant enough to create land bridges which could have allowed man to move and exist in areas often never considered as landmasses. It made some pretty big speculations on the degree of accuracy of research and the validity of events, but was honest in making it be known that cold, hard facts could not be concluded from the research. None the less, the research was out on a limb, but its speculations brought me much curiosity and interest.
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smithdb1@m... - Re: Reflection #6: Sea Level Change Through the Last Glacial Cycle (2004)
2/26/04; 12:29:08 AM (reads: 41757, responses:
0) |
The authors of this article examine the past fluctuations in sea level as it relates to glacial cycles, changes in the mantle of the earth, and shorline changes. They provide plenty of examples to show that sea levels over the world have changed more than once. They use observations as well as studies in geoloical, atmospheric, and fossil evidence for their findings for changes in sea level.
The authors found evidence in previously exposed shorline and fossil evidence in the form of corals and other sea life to show that sea levels were at lower levels. They then found evidence to show in changes of plate tectonics are related to changes in sea levels. The weight of the ice during glaciations have compressed the mantle causing it to adjust and cause changes in sea levels. Further evidence for changes in sea level are findings in the bottoms of the ocean. Studies have shown that a land bridge once existed between Australia and Tanzania, which indicates a lower ocean level.
I think that the evidence for sea level changes given by these authors went farther than just showing models of how glaciation has caused sea level to decrease. The authors used geological and fossil evidence to show how glaciation is directly related to changes in sea level.
I think that evidence for changes in sea level as it relates to glaciation or deglaciation shows us that sea level could change in the future. If the climate is warming, glacial ice could melt, causing a change in shape of the mantle as less weight is put upon it near the poles, which then could cause sea levels to rise globaly. Information on predictions of how sea levels could change with climate could show us how much sea levels could rise at current rates of warming.
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carveykn@m... - Re: Reflection #6: Sea Level Change Through the Last Glacial Cycle (2004)
2/26/04; 2:47:27 PM (reads: 41743, responses:
0) |
The authors related sea level changes to different aspects of the earth, mainly glaciers and glacial patterns. The evidence used was interesting, such as shorelines and fossils found along them. They used several different approaches, from the biosphere (ie, what types of life forms were living where and when) to the lithosphere (plate boundries and tectonics) to prove their point. The authors utilized the topography to demonstrate examples like land bridges which would indicate lower sea levels at one point in time. Glacial cycles were incorporated slightly as well, such as the ones we have looked at like D/O.
The authors had a variety of examples to prove their point overall. However, while we have been talking and discussing the subject, I suppose another article aobut sea levels fluctuating not only fails to surprize me but I am left hardly touched seeing that this has been proved over and over again to be true.
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dormancs@m... - Re: Reflection #6: Sea Level Change Through the Last Glacial Cycle (2004)
2/27/04; 12:39:52 AM (reads: 41792, responses:
0) |
In this article the authors discussed the correlation of the history of sea levels around the world to events such as glaciation and changes in the mantle of the earth. I learned that sea level does not simply rise whenever ice melts and fall when it freezes, there are other factors that influence it. I found one of the most interesting aspects of the topic to be how the weight of the ice effects the surface of the earth by causing bulges to form. Several methods were used to find the history of sea levels. These included fossil records, shorelines and plate tectonics. For example, fossils of corals that are now found above sea level can be dated to find how long ago the area was submerged.
Overall I found this article to be interesting, but somewhat daunting. I had to read several sections multiple times before I fully appreciated what the authors were saying. I also found the equations presented to be difficult to comprehend, but this could be because I am not as familiar with this area as the anticipated reader is.
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panzake@m... - Re: Reflection #6: Sea Level Change Through the Last Glacial Cycle (2004)
2/29/04; 8:24:30 PM (reads: 41646, responses:
0) |
| What was done?
Lambeck and Chappell, the authors of this article, present the relationship between sea level changes and glacial activity. The changes in ice sheets size causes spatial and temporal patterns. They go on to explain how certain observational data is limiting in this area, but that some patterns are evident. They present several other ideas that give support for their argument, including glacial isostasy, information on ice volumes, mantle viscosity, and shoreline reconstructions.
What was learned?
I have learned that through this evidence the relationship between glacial activity and sea levels due in fact follow identifiable patterns. I also learned some interesting things that I had never known before. The information in the observational evidence section they explained certain techniques for measuring sea levels in the past.
This article was pretty difficult to follow. I feel like I took in the jist of it, but the details and some of the concepts are over my head. This article, like some of the others, doesn't just teach you the facts of the article, but also how to break down and carefully read these types journals.
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maikutdl@m... - Re: Reflection #6: Sea Level Change Through the Last Glacial Cycle (2004)
3/1/04; 11:16:18 AM (reads: 41712, responses:
0) |
In this article, the authors looked at the sea level fluctuations in the past. They used coral reefs as one of their observations to find evidence of sea level fluctuation and what may have caused it. The evidence in the coral can be dated with both radiocarbon and uraniun-series methods. Most of the information scientists were able to gather was after the most recent deglaciation because past evidence has been destroyed rising sea levels at the onset of deglaciation or by advancing ice sheets leading up to the glaciation. The authors looked at many aspects such as Glacial Isostasy, Ice Volumes through the last glacial cycle, mantle viscosity, and shoreline reconstructions.
I'm not sure I quite understood some of the things the scientists were looking at (such as the glacial isostasy) but overall, this seemed really interesting. It is always fun to learn what is going on around the earth that we are unaware of.
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caritymr@m... - Re: Reflection #6: Sea Level Change Through the Last Glacial Cycle (2004)
3/1/04; 3:06:02 PM (reads: 41792, responses:
0) |
In this article, the authors are attempting to link sea level change with growth and decay of ice sheets. Intuitively, this makes sense, however I can see how other factors could also play into sea level change as well. By using different methods scientists are able to deduce past sea level heights. Examples cited in the article are tree stumps that may now be submerged (indicating water would have been lower so the tree could root) or fossilized coral reefs, indicating that the water level would have been higher for a substantial amount of time, so that the reef(s) could form. The authors propose various methods for identifying sea level height and also talk about how each of these methods has drawbacks, but nonetheless serve as a reasonable baseline for identifying past sea levels. Both sea level height as well as age are being gagued from these methods of collecting data. I'm a little perplexed as to why researchers would prefer this method over, say, collecting ice or sediment cores. The results seem (thus far) to carry more elasticity. The authors of the article sort of discount some of their methodologies as being rather flimsy. I guess a tan would be better than frostbite, though!
Ummm.... about these formulas -- (whispers) I'm not really understanding them!
Researchers also employed an interesting technique to study the feasibility of whether or not the Earth's crust and mantle could even support the weight of mass quantities of ice. They reasoned that due to the mantle's viscosity and the crust's elasticity, there should be no reason that the Earth could not have had large amounts of ice on the surface at one time or another. Another interesting method employed was shoreline reconstruction. The ways the researchers set about looking at this data was to collect information on where estuaries would have been found (or could have been found). Understanding that an estuary is where saltwater meets freshwater, one could assume this was relatively close to the shoreline. Pretty cool stuff.
This article provided a ton of information, and was (to me) pretty overwhelming. I'm not sure I completely understood all of the topics presented (like the equations!), but for the most part I think I could manage.
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Gattje@m... - Re: Reflection #6: Sea Level Change Through the Last Glacial Cycle (2004)
4/4/04; 6:54:40 PM (reads: 41711, responses:
0) |
In this paper, Lambeck and Chapell researched sea level changes through the last glacial cycle by looking at things like coral reef fossils, laminations, and carbon dating in order to determine when sea level fluctuations occurred. They found some patterns to be evident and were able link sea level change with growth and decay of ice sheets. This idea makes sense, but there are many other factors that go in to the change in sea level.
I still didn‚t really get what this article was trying to say, it was hard to understand because I didn‚t understand some of the vocabulary and the equations they used were very complicated and hard for me to understand. Basically, I understood the main idea that sea level changes aren‚t just from the melting of ice, but it is dependent upon many other things such as techtonics, density, viscosity, and isostacy. <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /><o:p></o:p>
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panzake@m... - Re: Reflection #6: Sea Level Change Through the Last Glacial Cycle (2004)
4/13/04; 8:52:23 PM (reads: 41629, responses:
0) |
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The authors of this article, Lambeck and Chappell, present information on sea level changes through the last glacial cycle. They state that sea level change through the Quaternary is a result of cyclic growth and decay of ice sheets. This results in a spatial and temporal pattern. The evidence that they say is most imortant for this theory is raised or submerged shorelines. The exposure of underwater features or the submersion of terrestrial features shws the change in level.
Glacial Isostasy shows spatial variability because of depressions on the earth caused by the ice load that had once sat on top of it. In addition they also measure Mantle Isostasy. Depressions in the mantle layer of the earth can also be an indicator that a glacier was once there.
This article is pretty informative. From it I would say I learned some major causes of sea level changes during the Quaternary. |
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Doug - Re: Happier than a Fox on a Beach with Peanut Butter
2/21/05; 11:33:53 AM (reads: 40376, responses:
0) |
What was done:
This article focused mainly on the changes in ice shelf mass and the corresponding changes in sea level. Also included was a discussion of isostasy (and some handy-dandy equations that derive the change in sea level due to isostasy) and a brief section on shoreline reconstruction.
What were the methods:
The authors used mainly temporal data and locations of ancient shorelines (to show sea level variability) to support his claims. I do have some slight concerns about the latter data set, because I cannot imagine how difficult it is to collect such data. The claims made meow through isostasy are completely derived from the equations listed in the article. The data does seem (with startling accuracy) to follow clear patterns, and there are not very many changes necessary to add a trend line.
What was learned:
The data shows the cyclitic nature of sea level variability. Also the article showed that some (or all?) global sea level change is due to tectonic activity and that local sea levels are tied into climate (and therefore ice sheet masses). Also (something that I found interesting), is that glacial effects are dependent on mantle conditions. And since that the mantle vscosity is different all over the world, this makes it much more difficult to calculate glacial impacts.
How this article changed my way of thinking:
Before I read the article I thought that ostriches were mean. And after reading the article, quite frankly, I still do. But in all seriousness this article did teach me a lot. I never knew about the differing viscosity of the mantle (I thought if it did differ, it was probably negligible). I also never knew that global sea level could be tied into plate tectonics. I thought both local sea level and global sea level would be caused by exactly the same things.
Fun Fact: Cy Young is the all time winningest pitcher with 511 career victories.
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Doug - Importance of Plate Tectonics When Discussing Sea Level Change
2/22/05; 6:31:53 PM (reads: 40206, responses:
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Amy Barton
The change in sea level during the Quaternary was examined
in this article. The main reason for sea
level change during this time was the retreat and advance of glaciers, but
other factors include tectonic uplifting and mantle viscosity. Sea level was measured by observational
evidence such as fossil coral reefs and submerged tree stumps and mathematical
equations. Once sea levels have been
determined, it becomes possible to predict shorelines and the migration of flora
and fauna. The main result the authors expressed was that sea level
change was/is the response of plate tectonics.
When the sea level changes, not all areas are affected in the same
way. For example, when glaciers melt the
change is spatially variable because of the deformation of the earth≠s ocean
surface. Thus, one area could experience
an increase in the sea level, while one area could remain the same. Once sea levels changes are figured out,
shorelines will be able to be reconstructed, which can aid in understanding the
migration of species.
Sea level change generally follows a cycle. As reported in earlier articles (as well as
this one), this cycle is largely the result of the growth and decay of ice
sheets. This article, however, helped me
to better understand the relationship between sea level change and plate
tectonics. Also, I had no idea that
mantle viscosity can have an impact on glaciers and thus sea level and climate.
This article made me more aware of the importance of
figuring out past ocean levels. Once
these levels are found, models can be made and used to predict the migrations
of many species. One
example that the
article used was the migration of humans from
<st1:country-region><st1:place>Australia</st1:place></st1:country-region>
to
<st1:State><st1:place>Tasmania</st1:place></st1:State>
using the <st1:place>Bass Strait</st1:place>.
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Zach Moning - Re: Tectonic Seas
2/23/05; 7:15:19 PM (reads: 40302, responses:
0) |
This article discusses the changes in sea level as it relates to the
deglaciation of the Earth. The authors, Lambeck and Chappell, used
mostly observational data pertaining to ice volumes, glacial isostasy,
shoreline reconstructions, and mantle viscosity. The data shows
correlation between the ice shelfs and global sea level.
I was previously unaware of the cyclic nature of sea level and ice
shelf mass. I was also unaware of how tectonic activity causes so much
grief in terms of glaciation. It makes sense, I suppose. Breaking off
ice sheets is a plausible result of tectonic activity, and we learned
recently that such activity could change sea level.
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Adam Brule - Re: Reflection #6: Sea Level Change Through the Last Glacial Cycle (2004)
2/23/05; 7:16:11 PM (reads: 40246, responses:
0) |
What was "Done" (methods. true source of data)?<o:p></o:p>
Kurt Lambeck and John Chappel
specifically focus on the historical changes in sea level in many regions of
the world. They correlated sea level
patterns to ice sheets by observing submerged tree stumps, coral reefs, and
other deposited materials. Lambeck and
Chappel looked at water and ice isostasy using complicated mathematical
formulas to analyze ice sheet melting and their corresponding sea levels in
different locations. Again sea level arises from complex interactions between
plate tectonics, mantle viscosity, and isostasy.
What does this mean?
This means that sea level is
affected at so many levels and that particular fall or rise in one area doesn‚t
mean it can be globally applied. As
evidence from the exposed shorelines were the authors found evidence in the
stumps, coral, and deposited material they found that sea levels are highly
variable based on many factors. „The
relative sea level change therefore exhibits complex temporal and spatial
patterns that contain information about a range of Earth and climate
processes‰.
How did/will this article change my thinking?
This article was littered with
complex formulas and mathematical calculations to make predictions on terms
that were all but hardly familiar. The
graphs did illustrate their point and provided some useful and interesting look
into relationships between glacial activities and sea levels. They did outline several methodologies that
were fairly interesting to follow on because they had thick descriptive reasons
for coming to certain conclusions.<o:p></o:p>
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Jason Fox - Re: Reflection #6: Sea Level Change Through the Last Glacial
2/23/05; 8:46:43 PM (reads: 40224, responses:
1) |
Method: The two authors, Kurt Lambeck and John Chappell, looked at
fluctuations of sea level around different parts of the world during
the last glacial period of Earth. Their theory is that by looking that
the changes around the world, they are able to predict the condition of
Earth's climate thousands of years ago as well as the reach and
location of ice sheets. One of the key facts is that the level at
different parts of the world has either risen or fallen at different
rates, depending on what part of Earth is being looked at. Different
tests were created in order to discover exactly the shifts in the rate
of change. Total sea level change was calculated with a very complex
math formula, that took into account the surface area of the ocean, the
densities of sea water and ice, and other contributions.
Results: The final results take into account the history of ice sheets
during the last glacial cycle and the shifts of mantle viscosity during
the same period of time. All of this information is used to construct
what the shoreline was in the past, primarily in the Bass Strait, the
area between mainland Austrailia and Tasmania. It seems that there is a
shift between flooding of the Strait and a much dryer bed. Mostly, it
is always a channel between the two islands, and was never dry enough
to act as a land bridge between the two land masses.
What I got: I'm not exactly sure how it pertains to Global Climate
change. To me, it's just another attempt by scientists to try to
construct what the climate of the past was like beyond Europe and North
America. I do think, that this is one of the most stable attempts that
I have read about so far. This study starts out by looking at exisiting
evidence that anyone can see if they look hard enough. Through this
base evidence, hey take their own math formulas and theories to try and
construct the past.
Will it change my thinking? Not really. This is just the same old stuff
that we have been reading for the past few weeks, and I can see that we
are merely looking at different theories about the climate or our Earth
thousands of years ago. Like I said before, this one I thought was a
little more concrete, and I could believe some the claims that these
two were making. I don't know how it will connect with the presentation
this week.
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Bryan Glosik - Re: Reflection #6: Sea Level Change Through the Last Glacial Cycle (2004)
2/23/05; 11:24:04 PM (reads: 40312, responses:
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The main focus of this article was to study the change of sea level during the Quaternary. Various aspects such as ice decay and glacial formations along with tectonic plate activity were attributed to the change in sea level. Most of the data that was collected to prove the sea level change was done through shoreline studies. Things like fossilized coral reefs and submerged tree trunks along the shore gave indications of past sea level height. The article also included a section on isostasy in relation to past sea level. Figures were also given to convey the inforamtion gathered.
The author seems to believe that one of the main causes of the change in sea level was due to suprisingly plate tectonics rather than glacial activity. Glacial melting and development does not always affect all the oceans. It may affect one area but not another. The mantle viscosity plays a major role in how much the glaciers can affect sea level. The mantle viscosity varies very widely all over the world making it a complex puzzle. The author also references that learning more about past sea level may help trace the path of human migration.
This artilce brought new light as to why past sea level is important. It allows us to gain a better understanding of not only climate but human migration from continent to continent. I was also unaware of the vast impact the mantle influences on glacial behaviour.
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willis okech - sea-level history
2/24/05; 1:25:19 AM (reads: 41853, responses:
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The authors Lamberck and Chappel looked at Sea level changes over the years with respect to the last glacial cycle. 8 models of spartial sea level change since the Last Glacial Migration (LGM) were looked at. These were: Angerman, Gulf of Bothnia, Sweden; Andoya Nordland, Norway; South of England; Hudson Bay, Canada; Barbados; Bonaparte Gulf, north-west Australia, Orpheus Island, North Queensland, Australia; and the South Shelf southeast Asia. The authors looked at glacial isostasy, Ice volumes through the last glacial cycle, coral reefs, transitions from freshwater to marine deposits, Mantle viscosity was also looked at to estimate past ice volumes. In addition to predict future sea level changes, shoreline reconstructions were also looked at.
Various data from other authors was looked at in addition to Lamberck and Chappel≠s observational evidence.
The evidence found that even though ice melt and decay has affected sea level changes over the years, there≠s more to the causes of sea level change than just glaciations and deglaciation. Other theories that they put through were plate tectonics and mantle viscosity.
In fact till this article, I hadn't thought much about sea level changes and causes. I knew from past reading that sea levels had been different from the past. So the information given here was new ground and very informative. Of course it would be wise to look at what other authors say about causes of sea level change. It was interesting to read about the link between past sea level changes and past human migration across the Bass strait.
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Sophia Turczynewycz - Re: Reflection #6: Sea Level Change Through the Last Glacial Cycle (2004)
2/24/05; 9:24:47 AM (reads: 40211, responses:
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The authors of the article, Kurt Lambeck and John Chappell, researched the changes in sea lvel that occurred through the last glacial cycle and hte impacts these changes have had. Theyy examined these sea level changes and how they are related to glacial events, the earth's mantle, and the reconstruction of shorelines. They used equations and graphs to model these changes. Throughout their studies, they note that "Many of the factors contributing to changes in sea level are linked, either through physical processes or through observational evidence, and the success of hte outcomes of the various sea level studies depends very much on the ability to separate the different contributions to the observational record."
From all the research and data collected, it was shown that sea level is affected in so many different regions of the world by all kinds of factors. Like the authors stated, "The relative sea level change therefore exhibits complex temproal and spatial patterns that contain information abpout a range of Earth and climate processes." Many factors affect how sea level rises and falls, not just when the ice melts and freezes. One thing the authors realized was that a lot of these sea level fluctuations are a result of plate tectonics.
Much of the concepts presented in the article were new for me, especially concepts such as glacial isostasy with all of its fancy shmancy equations. The article is similar to those previous read in its collection and research of past data collected to understand earth's processes, and I never realized that these sea level changes were a result of plate tectonics, and not just the freezing and melting of ice.
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Caitlin - Re: Tectonics is Playing You for a Foul?
2/24/05; 10:45:02 AM (reads: 40194, responses:
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-What was "Done" : Finding evidence of sea level changes can be very tricky because many things factor into it. Whether it be physiological or observational evidence, the key is to be able to seperate the two when determining real evidence. Using such things as tree root lines, coral inhabitance, estuary formations, and tectonic elevation, and shoreline reconstruction can all be very usual when looking for observational evidence. Glacial Isotasy helps determine the Earth's surface deformation and graviational pull in effects to teh sea level changes form glacial areas. There are other measurements using the mantle viscosity adn glacial cycle ice volumes to find evidence.
-What was learned: I didnt realize that there were so many ways to find evidence for sea level changes. Som eof the evidnece they had foudn seemed to me not to be the best evidnece only because it had other things that need to be factored into it to make any sense.
-What it means: Im not sure what this article is suggesting. In some cases I feel lke it was pulling for the whole its the end of the world global climate change stuff and then there are other cases like yeah some trees have longer roots here now.
-How did/will this article change my thinking: The only thing that changed my thinking was a statement right in the beginning where they mentions tectonices and the sea level rising in the Southern Hemisphere in some areas and then in the Northern Hemisphere it was becoming lower. It made me think that maybe there area jsut shifts happening due to the plates colliding and maybe all these measurements mean nothing.
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Kate Echement - Re: changes in sea level
2/24/05; 11:10:27 AM (reads: 40220, responses:
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What was done:
Lambeck and Chappell observed the sea level changes that occurred since the last deglaciation. Their main evidence for sea level changes can be seen in the form of raised or submerged shorelines, which are indicated by fossil coral reefs. They were able to time the transgressions based on radiocarbon dating analysis of materials near the transition. They also looked glacio-hydro-iostatic contributions responsible for spatial variability using complex mathematics, ice volumes, and mantle viscosity.
What was learned:
There are still a lot of unanswered questions for some areas such as Siberia. Information is also limited about ice cover near the Antarctic ice shelf, and there is no information about how thick the ice was during the last LGM. However, it is possible to estimate sea level changes in Northern Europe and North America. They estimate that glacial melting began about 19,000 years ago and ended ~7,000 years ago. Rates of equivalent sea levels were estimated to be 15m in 1000 years. A rapid change in events during the oxygen isotope stage 3 coincide with Heinrich ice-rafting events observed in the North Atlantic sediments; sea level fall during this period occurs in short time intervals and ice accumulation appears to have been a rapid process. They also noted that the upper mantle viscosity is representative of average ocean and continental mantle values; average viscosity for the lower mantle exceeds that of the upper mantle. In the end all this analysis helps to notice the earliest migration periods of humans in Tasmania
What did I get out of this:
Most of the science behind this study is relatively new to me, and over my head especially the math. However it was interesting to see the different sea level changes that occurred during the last deglaciation especially when incorporating human migration movements.
How did this change my thinking:
As I said, most of this was new to me, and as hard as it was to read I found it interesting. It will be even more interesting when they will be able to test hypotheses about migrations of flora and fauna across the once shallow seas.
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Laura Jones - Re: Reflection #6: Sea Level Change Through the Last Glacial Cycle (2004)
2/24/05; 11:28:13 AM (reads: 40182, responses:
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| The authors studied the changes in sea level in conjunction with the formation and recession of ice sheets. They gathered their data from coral reefs and submerged tree stumps and deposits of organic materials. They also used equations that I couldn‚t quite follow to discuss isostasy.
On of the conclusions of the article is the important of plate tetonics in the changing sea level, as well as mantle viscosity, which varies regionally. The authors basically say that there are a lot of different factors that contribute to sea level change, and it can‚t be easily explained by one thing.
The idea that not only glaciers, but also plate tetonics could affect sea level was entirely new to me. It seems like most of the articles we‚ve been reading come to the same conclusion- its difficult to explain large-scale changes by simple cause-and-effect relationships.
One of the most interesting parts of the article for me was the section about the Bass Straight between Australia and Tasmania, probably mostly because the diagrams helped make it really understandable. Especially since I found a lot of this article difficult to understand, especially the math.
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Justin - Species Diversity?
2/24/05; 1:54:20 PM (reads: 40226, responses:
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Many sources were examined to look at sea level changes throughout history as they relate to glacial events, properties of the physical composition of the earth's layers, and changes in coastal structure. They graphed sea level changes against time, position, ice volume, and water depth.
What they found was that the sea level changes were caused by plate tectonics. The weight of the ice during glaciations compressed the mantle causing it to adjust and change in sea levels.
Well, I think the idea is an intersting one. I'm not sure if it proves that much. But hey, I did learn something from it.
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George-Paul Richmann - Re: Reflection #6: Sea Level Change Through the Last Glacial Cycle (2004)
2/24/05; 2:42:11 PM (reads: 40176, responses:
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What was done?
The sources of data included various sources of sea level data. This included fossilized reefs, topographic information (shorelines, etc). Additionally, geophysics was used to determine the effect that the massive weight of ice on the contents would have on the mantle and then apply those effects to sea level.
What were the methods?
They were able to look at the physical history of ocean levels and then use that to develop an approximate formula that correlates glaciers, sea level etc. The concept that the paper developed was glacial isostasy.
What was learned?
That glaciers have an effect on now the mantel 'holds up' the asthenosphere, and this in turn has an effect on the level of the ocean. It was also found out that there is a 'lag' in the effect that the ice has on the mantle and a return from that effect once the ice is no longer there.
How did it affect my thinking?
I was amazed to what extent glaciers were able to affect the mantel. Within the article it said that as much as 2000m to 2500m of ice formed huge glaciers. While I was aware that glaciers have a profound effect on the topography what we see (hills, mts. valleys, etc). I was surprised to learn that the glaciers actually had an effect on the mantel, and that contents actually Œdrooped' under the pressure of the ice. Additionally, I was really pleased with some of the implications that the author was able to draw to history. By using Kurt's reconstruction of sea levels a better understanding of human development was attained.
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Steven Schwark - Re: Reflection #6: Sea Level Change Through the Last Glacial Cycle (2004)
2/24/05; 3:57:07 PM (reads: 40251, responses:
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The authors spoke about the correlation of sea levels around the world to events such as glaciation and changes in the core of the earth. When it comes to sea level change, they pointed out that it is not simply the melting and freezing of water, but many other significant effects. One interesting topic was how the Earth itself can bulge in certain places due to the ice freezing in particular areas. The history of sea levels was also examined, including fossil records, shorelines and plate tectonics.
Overall I found this article to be interesting, but somewhat overwhelming. The information presented, once comprehended, was insightful and unique, but overcoming the task of picking it out of the thick wording and obtuse language was difficult.
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Rob - Re: Reflection #6: Worst...Article...Ever
2/25/05; 12:28:16 AM (reads: 40174, responses:
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| The article primarily focused on sea level change through the Quaternary using complex data collection methods and observations. Observations such as coral beds surviving through periods of glaciation (low seas) and interglaciation (high) yielded the visible data for scientists in making claims for periodic trends in ice shelf fluctuation. In their views, seal-level fluctuation is a direct result of advancing or retreating ice sheets from Greenland, which, in turn, is the direct result of far reaching climatic shanges (i.e. Milankovitch connection). Several equations on isostasy were also discussed to explain a critical glacial-hydro-isostasy contribution to the spatial variability and gravitational consequences of ice sheet breakup. Whatever that means.
Some of the methods used to collect visible evidence of shoreline shifts coinciding with glaciation and climatic shifts were unique. Methods such as the observation of sea level positions between tree-root sediment and the reefs at the time of coral growth gave the scientist a range of values to work from. Series of data from patterns in regional basins were compounded together to give a detailed and contrasting depiction of sea level fluctuation (some higher as a result of glaciation, some lower). An Interesting conclusion from the research was the highly-studied relationship between sea level conditions and tectonic activity. I found this fascinating because rarely have I heard of glaciation being tied directly with conditions in the earth‚s mantle, suggesting a more advance system of oceanic basins then previously thought.
I feel that most of the temporal data and collection methods were very interesting yet the presentation of the topic as yet another dry and tawdry collection of data and analyses are played far too often in the scientific articles. As an architecture student educated in the area graphic presentation, there is a certain aesthetic that is missed time and time again in scientific research that could really benefit the authors as an educational tool. For example, the use of calculations to explain some gravitational phenomena in relation to earth‚s ice sheet concentration was an interesting idea yet suffered from a horrible execution in keeping our interests or even attempting to be coherent. With its jumble of schematics that assumes pre-existing knowledge on the matter, I really didn‚t learn anything from the article after that point and it‚s a shame because I‚ve gotten a lot more out of more technically demanding areas of research in the past. These few, albeit, instances were the result of carefully executed and graphically coherent presentations of the data as an educational tool, not a battle for scientific superiority.
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Jacob Schober - Re: Reflection #6: Sea Level Change Through the Last Glacial Cycle (2004)
2/28/05; 1:45:38 AM (reads: 40076, responses:
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This article is about the change in the sea level during our last glacial period. The article was written by Kurt Lambeck and John Chappell. Their affiliation to any type of organization or research group is not noted. Alot of hard data is included in this article and there are many references used, which shows that they research is at least somewhat legitimate. The first thing i noticed about this article was the topic itself, and did not really lead into any new information. As far as my understanding of the topic is that the sea level obviously dropped during the last glaciation or any glaciation for that matter. This indeed proved to be true (i think), although it appears that the sea level did indeed drop, but was still higher than it is now. I found this to be very interesting. Examining a topic of this much history takes in so many variables i find it difficult to find the exact accuracy of his data, but i do think the estimates are legitimate based on the wide range of data. The authors took in and examined a number of these different variables such as tectonic uplift, glacial isostacy and mantle viscosity (among others), which only adds to the data's validity. I especially found how they could gauge this tectonic uplift in correlation with sea level data. For instance, if they found sea coral 100 m above current sea level, how would they know how much of that is due to uplift and how much due to the sea level at the time of the coral?
In this article it was hard to follow much of it because of the scientific wording and the shear amount of information they were giving you, but I do find the article to be fairly valid and their arguments seem to be backed by alot of information. Granted, i do not understand much of this information, but it is there. I learned alot about what kind of data is needed to research a topic like this and what different kinds of data need to be analyzed. Generally i would not read this article for leisure shearly because it was complicated and hard to follow, but for someone who is an expert in this field I would suggest it as a legitimate research article.
-Jacob Schober-
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Emily Barcelona - Re: better late than never...
3/14/05; 11:01:47 AM (reads: 41361, responses:
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what was done:
Kurt Lambeck and John Chappell have looked at periods of glaciation and deglaciation and their influence on sea level. The Glacial Isostasy equation is used to calculate the fluctuation of ice sheets over time. They also address mantle viscosity and shoreline reconstructions throughout the remainder of their article.
what was learned:
After reading this, I had more questions than answers. They talk about the discrepency between servey areas. One example is the fact that in the past 9000 years, sea level has fallen nearly 200m in Scandinavian Angerman and is near prestent level in Andoya. How can sites so close in physical proximity be so varying in sea level changes? I found it intersting that they could link mantle viscosity to the "changes in surface loads" that result from varying glacial periods.
what i got out of this:
I learned that although sea level records can be used to correlate glacial periods to sea level, not all records support our current thought about when and where glaciers were. If two areas in Scandinavia can yeild such varying results, how can we make any correlations. The math, like Milankovitch's stuff, is way beyond me, and I can only hope to eventually see how others apply this equation to what they are studying.
how did it change my thinking:
Like many of the articles we read in this class, this one changed my thinking by making me question our current beliefs about sea level changes. How much do we really know about the past when the areas that the records are kept keep being submerged and moved elsewhere? Seems like a big guessing game to me.
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Alyson - Re: Reflection #6: Sea Level Change Through the Last Glacial Cycle (2004)
4/8/05; 2:12:36 AM (reads: 39456, responses:
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What was done?
The authors use various techniques and studies to show how and why sea level changed through the last glacial cycle. They discussed observational evidence, glacial isostasy, mantle and lithosphere viscosity, and tectonic events as possible factors working together to affect sea level over time.
What was learned?
Sea level fluctuation depends on many factors and is usually spatially restricted; in other words, sea level can change differently in different regions over the same period of time (increase in one part of the world while decreasing in another). Observational evidence can say a lot about sea level fluctuation in an area. For example, if a tree stump is found submerged in the ocean it is a fair assumption to say that sea level used to be lower than the roots of the tree at this location. The authors also identified glacial isostasy as a major factor in sea level fluctuation. The exchange in mass between a melting/freezing glacier and the sea changes sea level locally. Also, basin morphology of the ocean can be changed with removal of large weights of ice, which can also affect sea level. The same principle is present when discussing mantle and lithosphere viscosity. Finally, the authors discuss how tectonic events can change sea level by changing ocean basin morphology.
What it means.
Many factors affect sea level, which makes it a complicated fluctuation. Although global climatic events may occur, they may not affect sea level the same throughout the world.
How did this article change my thinking?
It is interesting to note that sea level can rise in one part of the world while lowering in another. Other than this, this article did not really surprise me or affect my thinking about sea level change in any way. It did make me remember the fossil reef systems I saw in the Bahamas and what I learned about them then.
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Stanton Hugger - Re: Reflection #6: Sea Level Change Through the Last Glacial Cycle (2004)
4/25/05; 11:36:05 PM (reads: 39156, responses:
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| Lambeck and Chappell collected a host of data in order to tackle the
causes and effects of sea level changes during our last glacial
cycle. Much of the presented data was not collected by Chappell
and Lambeck, though its synthesis in this article helps to clarify the
myriad inputs related to sea levels. Among many of the
identifiers for a cause in sea level change illustrated in the essay
are the cyclic growth and decay of ice sheets in the poles, which
change the physical behavior of the oceans as a whole. The data
collected ranges from global to local samples throughout different time
periods. Using plate tectonic information, glacial signaling,
sediments, mantle viscosity, ice loads, radiocarbon dating, isotopes,
fossil corals, and even tree rings, the authors consider a variety of
oceanic, atomospheric, and geologic data in order to create a model
which can explain the trends of the past and potentially inform us of
future possibilities in sea level change. One of the more
interesting discoveries made by collecting this data was that land
stretches could have been exposed during interglacial periods and
allowed early humans and fauna access to and population of, now
isolated lands such as Australia and Tasmania! This type of thing
I am interested in because it takes what seem to be sterile chunks of
data concerning climate and sea level and translates it to a human
impact in the past.
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Jay Beck - Re: Reflection #6: Sea Level Change Through the Last Glacial Cycle (2004)
5/6/05; 5:38:03 PM (reads: 39080, responses:
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What was "done"? the authors looked at historical changes in sea levels from arround the glob. these were mostly obsevational numbers. they next attempted to relate sea level changes with ice meltings they also used very indepth and advanced(confusing) math to analize ice sheet melting and sea levels.
What was learned? they learned alot about how the interaction between sea levels and ice sheet melting. i learned that this may be a usefull article in my project on antartic relating it possible to sea levels
What it means? this dosent really mean a hole lot but at the smae time it dose. It means that melting alone or palte techtonics that raise sea level in one area wotn nessicarily effect the glob
How did/will this article change my thinking?It changed my views and prospective on the idea of melting sea ice and its correlation the global oceanic levels. It also made me think about obnject protruding from the water table such as rocks and stumps at local lakes and pond( dont know why)
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