The East Antarctic cryosphere in the instrumental period
- This page is part of the topic The ice sheet in the instrumental period
Changes are less dramatic across most of the East Antarctic ice sheet with the most significant changes concentrated close to the coast. Increasing coastal melt is suggested by some recent passive microwave data (Tedesco, 2008[1]). Satellite altimetry data indicate recent thickening in the interior that has been attributed to increased snowfall likely because of year-to-year and decade-to-decade fluctuations in snowfall (Davis et al., 2005[2]), but ice core data do not show recent accumulation changes as significantly higher than during the past 50 years (Monaghan et al., 2006a[3]). A resolution of this apparently conflicting evidence may be that there is a long-term imbalance in this area, which could possibly reflect a response to much more ancient climate changes. An alternate suggestion, based on direct accumulation measurements at South Pole, is that this thickening represents a short period of increased snowfall between 1992 and 2000 (Thompson and Solomon, 2002[4]). The absence of significant atmospheric warming inland, distinct from the global trend of warming atmospheric temperatures, may have forestalled an anticipated increase in snowfall associated with the global trend.
The only significant exceptions to this broad-scale quiescence of the East Antarctic ice sheet occur on the Cook Ice Shelf and in the mouth of the Totten Glacier where thinning rates in excess of 25 cm/year have been measured (Shepherd and Wingham, 2007[5]). It remains unknown whether these events are recent, or indeed, whether they are related to changing adjacent ocean conditions, as in the case of the Amundsen Sea outlets, or whether they are just longer-term responses of a regional dynamic origin. Both these areas are the outlets of the ice sheet occupying the two major marine basins lying beneath the ice sheet (Lythe et al., 2001[6]).
The mass balance of the East Antarctic ice sheet has been calculated by many research teams with various sensors and methodologies: +22 ± 23 Gt/yr (Rignot and Thomas, 2002[7]); -4 ± 61 (Rignot et al., 2008[8]); 0 ± 56 (Velicogna and Wahr, 2006[9]); and +15.1 ± 10.7 (Zwally et al., 2005[10]). The results range from near zero to slightly positive with some of the variations dependent on the time interval investigated. One of the most significant factors giving rise to this uncertainty is that, at present, an ad hoc interpretation of the thickness changes must be made to determine whether they represent changes in snow surface accumulation, and thus changes in low-density snow and firn, or whether they are dynamic in origin and represent a change in ice, which has a much higher density.
References
- ↑ Tedesco, M. 2008. Updated 2008 surface snowmelt trends in Antarctica, Eos. Trans., 89 (13).
- ↑ Davis, C.H., Li Y., McConnell, J.R., Frey, M.M. and Hanna, E. 2005. Snowfall-driven growth in East Antarctic Ice Sheet mitigates recent sea-level rise, Science, 308, 1898-1901.
- ↑ Monaghan, A.J., Bromwich, D.H. and Wang, S-H. 2006a. Recent trends in Antarctic snow accumulation from Polar MM5, Philosophical Trans. Royal. Soc. A, 364, 1683-1708.
- ↑ Thompson, D. and Solomon, S. 2002. Interpretation of recent southern hemisphere climate change, Science, 296(5569), 895-899.
- ↑ Shepherd, A. and Wingham, D. 2007. Recent sea-level contributions of the Antarctic and Greenland ice sheets, Science, 315 (5818), 1529-1532.
- ↑ Lythe, M.B., Vaughan, D.G. and BEDMAP Consortium, 2001. BEDMAP: A new ice thickness and subglacial topographic model of Antarctica, Journal of Geophysical Research, 106(B6), 11335-11351.
- ↑ Rignot, E. and Thomas, R.H. 2002. Mass balance of polar ice sheets, Science, 297 (5586), 1502-1506 AUG 30 2002.
- ↑ Rignot, E., Bamber, J.L., Van Den Broeke, M.R., Davis, C., Yonghong, L., Van Deberg, W.J. and Van Meijgaard, E. 2008. Recent Antarctic ice mass loss from radar interferometry and regional climate modeling, Nature Geoscience, 13 January 2008; doi:10.1038/ngeo102.
- ↑ Velicogna, I. and Wahr, J. 2006, Measurements of Time-Variable Gravity Show Mass Loss in Antarctica, Science, 311, (5768), 1754 DOI:10.1126/science.1123785.
- ↑ Zwally, H.J., Giovinetto, M., Li, J., Cornejo, H., Beckley, M., Brenner, A., Saba, J. and Yi, D. 2005. Mass changes of the Greenland and Antarctic ice sheets and shelves and contributions to sea-level rise: 1992-2002, Journal of Glaciology, 51(175), 509-527.
