|Centennial-scale Holocene climate variations amplified by Antarctic Ice Sheet discharge|
|investigators:||P. Bakker and others|
Little is known about the dynamical system formed when a marine-based ice sheet interacts with the global ocean/atmosphere circulation. While some understanding of this dynamical system can come from coupling ice sheet models to earth system models, this needs validation from observations on the relevant timescales of the coupled system. These timescales are likely to be multi-century, millennial, and longer.
This paper describes coupled simulations using a PISM-modeled Antarctic Ice Sheet (AIS) with incomplete coupling to the global circulation. On the one hand, the AIS model is forced by Southern Ocean temperatures from the LOVECLIM Earth System model, while on the other the modeled AIS meltwater is used to force the UVic global climate model. The model results are compared to high-temporal-resolution records of iceberg-rafted debris for the last 8000 years from two sites in the Scotia Sea, which provide a spatially-integrated signal of ice sheet variability in the Holocene. The model and data share variability at centennial and millennial frequencies. The primary conclusion is that fluctuations in AIS discharge caused by relatively-small changes in subsurface ocean temperature can amplify multi-centennial climate variability regionally and globally. A dynamic AIS may have driven climate fluctuations during the Holocene.
The 4000 square km ice field in Southeast Alaska is well-known and accessible since its outlets are in the suburbs of the Alaska state capital, Juneau. But climate data for the area are sparse.
Those model runs that agreed well with observations for 1971 to 2010 generated volume and area losses of more than half by 2099. While co-author Regine Hock (UAF) is quoted as saying “The massive icefield that feeds Alaska’s Mendenhall Glacier may be gone by 2200 if warming trend predictions hold true,”, the authors emphasize that spatially-distributed mass balance measurements and improved climate projections that resolve the local temperature and precipitation patterns are essential to solidifying these predictions.
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PISM is jointly developed at the University of Alaska, Fairbanks (UAF) and the Potsdam Institute for Climate Impact Research (PIK). For more about the team see the UAF Developers and PIK Developers pages.
UAF developers, who are in the Glaciers Group at the GI, are supported by NASA's Modeling, Analysis, and Prediction and Cryospheric Sciences Programs (grants NAG5-11371, NNX09AJ38C, NNX13AM16G, NNX16AQ40G) and by NSF grants PLR-1603799 and PLR-1644277.