How does rising atmospheric CO2 affect marine organisms?

Learn how plants respond to higher atmospheric CO2 concentrations

Click to locate material archived on our website by topic


East Antarctic Ice Sheet -- Summary
In light of the significant and possibly ongoing temperature increase experienced by the earth in recovering from the global chill of the Little Ice Age (the latter century of which warming is claimed by climate alarmists to be unprecedented over approximately the past two millennia), should we be worried about the melting of the East Antarctic Ice Sheet?

In a brief review of the status of the world's major ice sheets, Raymond (2002) bluntly states "there is little evidence that the huge East Antarctic Ice Sheet is responding to recent climate warming."  In addition, he notes that "the total mass of today's ice sheets is changing only slowly, and even with climate warming increases in snowfall should compensate for additional melting."

Anderson and Andrews (1999), on the other hand, conclude that "the current interglacial setting is characterized by a more extensive ice margin and larger ice shelves than existed during the last glacial minimum, and that the modern West and East Antarctic ice sheets have not yet shrunk to their minimum."  So, if there is a potential for further melting in response to additional warming, how rapid might it be?

Naslund et al. (2000) studied this question using a 10-km by 10-km data set on ice sheet bed and surface topography for western Dronning Maud Land as input to a time-dependent ice sheet model, which they used to simulate changes in ice sheet volume for this region of the East Antarctic Ice Sheet in response to six temperature forcing scenarios (5C instant warming, 5C slow warming, 10C warming, 5C instant cooling, 5C slow cooling and 10C cooling).  The model yielded a set of equilibrium responses that required something on the order of 20,000 model years to achieve, leading them to conclude that the East Antarctic Ice Sheet "may still be adjusting to the climate change that ended the Last Glacial Maximum," in harmony with the conclusion of Anderson and Andrews.

So what eventually happened in these model runs?  By the end of the 20,000 model years, the 5C warming and cooling scenarios produced changes in ice sheet volume that varied by only 1 to 1.5% of the initial ice sheet volume, suggesting that "the investigated part of the [East Antarctic Ice Sheet] does not appear to be very sensitive to present or future climatic changes," in harmony with the conclusions of Raymond.  Results for the 10C warming and cooling, for example, produced larger initial fluctuations in ice volume, but they quickly stabilized and returned to near initial conditions at the end of the 20,000 years.

That these results are reasonable is suggested by the findings of Marchant et al. (1993).  Based on an analysis of the preservation, age and stratigraphic relationship of an in situ ashfall layer with an underlying desert pavement in Arena Valley, southern Victoria Land, they concluded that a cold-desert climate has persisted there throughout the past 4.3 million years.  One implication of these findings, in their words, is that "the collapse of the East Antarctic Ice Sheet due to greenhouse warming is unlikely, even if global atmospheric temperatures rise to levels last experienced during mid-Pliocene times," which conclusion would appear to be right in line with the results of the model study of Naslund et al.

Going back even further in time, we find still more reason to discredit the notion that the integrity of the East Antarctic Ice Sheet is in any danger from rising atmospheric CO2 concentrations. Working with sediment cores obtained from three deep-sea drilling sites, Pagani et al. (1999) developed a history of atmospheric CO2 concentration over the period stretching from 9 to 25 million years ago (the early to late Miocene), determining that the air's CO2 concentration of that period was similar to levels characteristic of Pleistocene glacial/interglacial intervals, i.e., 180 to 290 ppm.  In the process, they found that at the height of the Miocene climatic optimum some 17 million years ago, deep water and high-latitude surface water temperatures were as much as 6C warmer than they are today, noting that it has long been generally believed that elevated atmospheric CO2 was responsible for the great warmth of that period.  Their finding that atmospheric CO2 concentration was "uniformly low" throughout the Miocene, however, led them to state that what they found "appears in conflict with greenhouse theories of climate change."  They also state that "there is no evidence for a sharp decline in [atmospheric] CO2 associated with EAIS [East Antarctic Ice Sheet] expansion" during the Miocene.  In fact, they note that "atmospheric carbon dioxide rises [our italics] following the expansion of EAIS," which is also in conflict with greenhouse theories of climate change.  And when theories conflict with reality ... do we really need to say that reality always wins?

Summing up, these several studies suggest that even the most catastrophic warming scenario produced to date by the IPCC would have little impact on the integrity of the East Antarctic Ice Sheet.

References
Anderson, J.B. and Andrews, J.T.  1999.  Radiocarbon constraints on ice sheet advance and retreat in the Weddell Sea, Antarctica.  Geology 27: 179-182.

Marchant, D.R., Swisher III, C.C., Lux, D.R., West Jr., D.P. and Denton, G.H.  1993.  Pliocene paleoclimate and East Antarctic Ice-Sheet history from surficial ash deposits.  Science 260: 667-670.

Nslund, J.O., Fastook, J.L and Holmlund, P.  2000.  Numerical modeling of the ice sheet in western Dronning Maud Land, East Antarctica: impacts of present, past and future climates.  Journal of Glaciology 46: 54-66.

Pagani, M., Authur, M.A. and Freeman, K.H.  1999.  Miocene evolution of atmospheric carbon dioxide.  Paleoceanography 14: 273-292.

Raymond, C.F.  2002.  Ice sheets on the move.  Science 298: 2147-2148.