An International Workshop
Antarctic Peninsula Climate Variability: Observations, Models, and Plans for IPY Research
Recent events in the Antarctic Peninsula (AP) demonstrate that ice and climate systems can change rapidly in a warming world. Air temperatures in the AP have risen six times faster than the global average in recent decades, which has triggered glaciological and ecological events in the last 1,000 years that are unique in the history of the region. Studies based on remote sensing and the available in situ data show that a complex interaction is underway, one that involves climate warming, air circulation changes, sea ice retreat, and surface and basal melting of land and shelf ice. Such changes have contributed to melt percolation and fracturing, seasonal fluctuations in ice flow, and rapid glacial acceleration in the aftermath of shelf breakup. As the shelves disintegrate, they uncover a glacial history preserved on the seafloor beneath them, indicating that the current retreats are rare to unprecedented in the Holocene. Biological and oceanographic studies are active along both coasts, as scientists strive to understand how ocean currents and ecosystems migrate during climate change. During a period of rapid change, the recent discovery of a new chemotrophic ecosystem native to the sub-iceshelf environment confirms that there are still unknowns in the AP's earth and life systems.
The workshop will review recent high-profile research results. Warming has continued in the AP area through at least 2003 (Skvarca and DeAngelis, 2003; Morris and Vaughan, 2003), and an exceptional weather pattern in 2002 led to both unprecedented summer warming and intense, prolonged surface melting, which culminated in the disintegration of the Larsen B ice shelf (van den Broeke, 2005; Rack and Rott, 2005, in press; Scambos et al., 2003). Subsequent to this disintegration, significant glacier acceleration and thinning occurred (Rignot et al., 2004; Scambos et al., 2004), confirming the link between ice shelf stability and glacier force balance. This had been previously suggested by observations of the Larsen A feeder glaciers and the valley walls of the Larsen B glaciers (Rack and Rott, 2002; DeAngelis and Skvarca, 2003). More broadly, a survey of aerial and satellite photos spanning 50+ years has shown that glaciers throughout the region north of 70° S are presently in retreat, and that this retreat progressed southward as climate warmed in the region in previous decades (Cook et al., 2005). There is substantial evidence emerging that many AP glaciers undergo seasonal accelerations due to meltwater percolation, which accelerates the mass balance changes in the ice sheet as the melt season lengthens.
Causes of the warming are uncertain, but several model-based theories are emerging with robust support from observation. Thompson and Solomon (2002) show that a large fraction of the warming is likely due to stratospheric cooling, a result of autumn ozone depletion. Raphael (2003) shows that the third-order wave in the circumpolar tropospheric circulation changed significantly around 1975, and the pattern now tends to force warmer, northwesterly flow across the peninsula.
Results from marine geological work are also stunning. Earlier work on the exposed Larsen A seabed, and in the Prince Gustav channel to the north, revealed that these areas had seen previous retreats of their ice shelf covering, coinciding with warmer global climate episodes in the recent past (such as the Medieval Warm Period, and the period between 2500 and 3500 BCE; Pudsey et al., 2001; Brachfield et al., 2003). But the retreat of the Larsen B in 2002 is apparently unprecedented in this interglacial (Domack et al., 2005).
The Antarctic Peninsula may well be a model for a future, warmer Antarctica. What we see there are changes of greater scale, speed, and magnitude than were considered possible before. The proposed meeting will be a step towards understanding this system and its responses, knowing what the future may hold, and planning future field observations and research.
This will be the third meeting in a series started in April 2002 on the topic of Antarctic Peninsula Climate Variability. Past meetings have been very successful, and have attracted a wide ranging international audience.
Cook, A., A. Fox, D. Vaughan, and J. Ferrigno. 2005. Retreating glacier fronts on the Antarctic Peninsula over the past half-century. Science 308, 541-544.
De Angelis, H, and P. Skvarca. 2003. Glacier surge after ice shelf collapse. Science 299 (5612), 1560-1562.
Domack, E., D. Duran, A. Leventer, S. Ishman, S. Doanne, S. McCallum, D. Ambias, J. Ring, R. Gilbert, and M. Prentice. 2005. Stability of the Larsen B ice shelf on the Antarctic Peninsula during the Holocene epoch. Nature 436(4), 681-685.
Domack, E., S. Ishman, A. Leventer, S. Sylva, V. Wilmont, and B. Huber. 2005. A chemotrophic ecosystem found beneath Antarctic ice shelf. Eos 86(29), 269-272.
Morris, E., and D. Vaughan. 2003. Spatial and temporal variation of surface temperature on the Antarctic Peninsula. In Antarctic Peninsula Climate Variability: Historical and Paleoenvironmental Perspectives. Ed. E. Domack et al. Special Issue, Antarctic Research Series 79, 61-68.
Raphael, M., 2003. Impact of observed sea-ice concentration on the Southern Hemisphere extratropical atmospheric circulation in summer. Journal of Geophysical Research 108 (D22), doi:10.1029/2002JD03308.
Rack. W., and H. Rott. In press. Pattern of retreat and disintegration of Larsen B ice shelf, Antarctic Peninsula. Annals of Glaciology 39.
Rignot, E., G. Casassa, P. Gogineni, W. Krabill, A. Rivera, and R. Thomas. 2004. Accelerated ice discharge from the Antarctic Peninsula following the collapse of Larsen B ice shelf. Geophysical Research Letters 31, L18401, doi:10.1029/2004GL020697.
Rott, H., W. Rack, R. Skvarca, and H. De Angelis. 2002. Northern Larsen Ice Shelf, Antarctica: further retreat after collapse. Annals of Glaciology 34, 277-282.
Scambos, T., C. Hulbe, and M. Fahnestock. 2003. Climate-induced ice shelf disintegration in the Antarctic Peninsula. In Antarctic Peninsula Climate Variability: Historical and Paleoenvironmental Perspectives. Ed. E. Domack et al. Special Issue, Antarctic Research Series 79, 77-92.
Scambos, T. J. Bohlander, C. Shuman, and P. Skvarca. 2004. Glacier acceleration and thinning after ice shelf collapse in the Larsen B embayment, Antarctica. Geophysical Research Letters 31, L18402, doi:10.1029/2004GL020670.
Skvarca, P. and H. De Angelis. 2003. Impact assessment of regional warming on glaciers and ice shelves of the northeastern Antarctic Peninsula. In Antarctic Peninsula Climate Variability: Historical and Paleoenvironmental Perspectives. Ed. E. Domack et al. Special Issue, Antarctic Research Series 79, 69-78.
Van den Broeke, M. 2005. Strong surface melting preceded collapse of Antarctic Peninsula ice shelf. Geophysical Research Letters 32, L12815, doi:10.1029/2005GL023247.