Image from Global Warming art project. Global sea levels are currently rising at a rate of about 3 mm per year 7. King et al. Most modern sea level rise, and sea level rise predicted over the next years, comes from ocean expansion and the melting of small glaciers and ice caps.
However, the amount that the sea level will rise in the future depends not only on temperature, glacier recession and ocean warming and expansion, but also the dynamic behaviour of the West Antarctic Ice Sheet.
Marine Ice Sheet Instability may result in rapid future sea level rise, contributed to by ice-shelf collapse and the dynamic behaviour of ice streams.
How much will Antarctica contribute to sea level rise in the future? You can read more about that in this blog post. The Antarctic Peninsula is particularly vulnerable to climate change due to its small size and northerly latitude 2. It interrupts the Circumpolar Westerlies and is liable to be affected by small changes in these winds.
Increased numbers of positive degree days 32 coincide with increased rates of thinning on Antarctic Peninsula marine-terminating glaciers, and increased meltwater ponding and hydrofracture on ice shelves. Glaciers are thinning and receding in response to warmer temperatures, and thinning glaciers are easier to float.
We know that basal melting of ice shelves drives ice sheet loss 34 , and we can observe the impacts of climate change around the Antarctic Peninsula today.
Go to top or jump to Glacier Recession. References 1. Turner, J. Antarctic climate change during the last 50 years. International Journal of Climatology 25 , Vaughan, D. Recent rapid regional climate warming on the Antarctic Peninsula.
Climatic Change 60 , Morris, E. Spatial and temporal variation of surface temperature on the Antarctic Peninsula and the limit of viability of ice shelves. Volume 79 eds. Domack, E. Mulvaney, R. Recent Antarctic Peninsula warming relative to Holocene climate and ice-shelf history. Nature advance online publication Changes in Antarctic temperature, wind and precipitation in response to the Antarctic Oscillation.
Annals of Glaciology 39 , Augustin, L. Eight glacial cycles from an Antarctic ice core. Nature , Solomon, S. Scambos, T. Ice shelf disintegration by plate bending and hydro-fracture: Satellite observations and model results of the Wilkins ice shelf break-ups. Earth and Planetary Science Letters , Glasser, N.
A structural glaciological analysis of the Larsen B ice shelf collapse. Journal of Glaciology 54 , Vieli, A. Causes of pre-collapse changes of the Larsen B ice shelf: Numerical modelling and assimilation of satellite observations.
Rack, W. Pattern of retreat and disintegration of the Larsen B ice shelf, Antarctic Peninsula. Climate-induced ice shelf disintegration in the Antarctic Peninsula. Cook, A. Overview of areal changes of the ice shelves on the Antarctic Peninsula over the past 50 years. The Cryosphere 4 , Rott, H. The Cryosphere 5 , Journal of Glaciology 57 , Hulbe, C. Patterns of glacier response to disintegration of the Larsen B ice shelf, Antarctic Peninsula.
Global and Planetary Change 63 , Glacier acceleration and thinning after ice shelf collapse in the Larsen B embayment, Antarctica. Geophysical Research Letters 31 , L Rignot, E.
Accelerated ice discharge from the Antarctic Peninsula following the collapse of Larsen B ice shelf. De Angelis, H. Glacier surge after ice shelf collapse. Reconstructed temperatures from the glacier length record are similar for low- and high-altitude glaciers Oerlemans a.
The dominant pattern of cool climate for a few centuries followed by warming beginning in the late 19th century is seen in all geographic regions examined, though significant differences in details exist. The most recent and comprehensive temperature reconstruction Oerlemans a uses glacier length records for a large number of glaciers Oerlemans et al. The information needed for detailed individual modeling for most of these glaciers does not exist, so the analysis instead uses an approximate and.
The black curve shows an estimated global mean value, obtained by giving weights of 0. B Best estimate of the global mean temperature, obtained by combining the weighted global mean temperature for — with the average of temperature records at earlier times.
The band indicates the estimated standard deviation. Reprinted with permission from AAAS; copyright Both the sensitivity of glacier length to temperature and the lag time for the glacier response are parameterized in terms of the dominant physical controls or correlates, which are topographic slope, annual precipitation, and glacier length itself.
The connection of these parameterizations to the underlying physics is supported in the technical literature, including detailed analyses of specific glaciers Oerlemans et al. However, these parameterizations are only expected to be accurate as an average for a large number of glaciers.
The sensitivity of glacier length to temperature arises from a fundamental aspect of glacial systems Paterson , Van der Veen , Oerlemans 1 : A glacier forming at high altitude will advance downward, extending its front into a region of net melt until all ice mass flux supplied from the high-altitude regions is removed by melt in the lower region.
Glaciers will always tend toward such a balance between mass inputs to the system and mass outflow, and this balance will be achieved with the glacier straddling the boundary between regions of net melt and net snowfall. Any climate change will affect this delicate balance and cause some adjustment of the glacier system. The dominant climatic influences are temperature and snowfall rate, though other variables such as cloud cover can be important in some situations.
A temperature increase in the overlying atmosphere increases the energy input to a melting glacier surface through increased downward longwave radiation and increased sensible heat transfer, increasing the rate of melt. An increase in temperature also causes more of the precipitation to reach the glacier surface as rain instead of snowfall.
Snowfall is the supply of new ice mass that sustains the glacier. A reduction or increase of the snowfall rate will cause the glacier to shrink or grow, respectively. Considering individual glaciers, snowfall changes can cause glaciers to advance and retreat, and this effect dominates in some situations e. Temperature is a more powerful influence on average, however, because the melt process only acts over a small fraction of the annual cycle and uses a small fraction of the total energy flux, so its capacity to change is large.
As a consequence, glaciers on Earth exist in precipitation regimes extending from the very wet temperate and tropical highlands down to the driest polar deserts, but are completely absent from environments spanning a large range of medium to high mean annual temperatures. In principle, it would be possible for the global population of glaciers to have shrunk over the past century due to a global-scale precipitation reduction.
However, there is no evidence of such a global drying Folland et al. Furthermore, focused studies of individual glaciers demonstrate the dominant role of temperature change in 20th century retreats Oerlemans et al. Here we are discussing only glaciers that terminate on land and are in warm enough environments to lose mass primarily by melt rather than iceberg production or sublimation. Dyurgerov and Meier , Dyurgerov Hence, it is reasonable to assume that precipitation changes induce variability or noise in the glacier length record but do not control its global mean pattern.
Regional patterns, on the other hand, are in some cases dominated by precipitation or other variables. Although warming in recent decades is an important factor driving glacier recession on Mt.
Kenya and the Ruwenzori summits, the much higher altitude glaciers on Kilimanjaro may be shrinking primarily as a continuing response to precipitation changes earlier in the century. The magnitude and importance of recent warming are still being researched. Temperature reconstructions based on glacier length and mass balance records are limited in their temporal and spatial resolution.
They do not provide a year-to-year view of temperature change, but only averages over several years to decades depending on the resolution of the length measurements and on the accuracy of assumptions in the physics. They do not provide any information about most of the globe prior to the 19th century. This section illustrates the evidence we use to determine the extent of past glaciation.
However, this is only a part of the story, as major ice ages occurred in the earlier geological past, as far back as million years ago. Indeed, there is a belief in some quarters that the world was almost totally covered by ice six or seven hundred million years ago - the age of the «Snowball Earth». The evidence for these earlier glaciations in the rock record is also explored. Glaciers online.
Crummock Water, with the Central Fells of the Lake District beyond is one of the classic glaciated areas in Britain, and one appreciated by many visitors. There are several lines of evidence for glaciation in ancient rocks.
One of the most useful is the presence of rocks mixed with particles ranging from clay to boulder size. These are exhumed examples dating back to Late Proterozoic time.
Rocks of glacial origin tillites , if they have not been tectonically deformed, sometimes weather in such a way that the stones can be removed easily. If the stones have been glacially transported, as this example from Late Proterozoic strata in Mauritania, they may retain striations, indicating abrasion as they were transported on the underside of a sliding glacier. One of the advantages of examining old rocks of glacial origin is that they are commonly well exposed.
China has abundant evidence of Late Proterozoic glaciations, spanning at leats three time intervals. Not only are there are extensive tillites, but there are grooved and striated pavements underlying them, as here in Henan Province.
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