Paper predicts increased precipitation in Antarctica will slow sea level rise by > 1 mm/yr

Comment by Frank Walters, elevated to a post:

I found an interesting paper: Antarctic precipitation and climate-change predictions: horizontal resolution and margin vs plateau issues, by C. GENTHON, G. KRINNER, H. CASTEBRUNET (Annals of Glaciology 50 2009)

The paper suggests that the INCREASE in snow and ice on the margins of Antarctica may cause the rate of rise in global sea level to be 1 mm per year LESS than the rate of rise otherwise expected..

The increase in sea ice can be linked to increase in precipitation on the margins of Antarctica. This is what one would expect intuitively, since the melting of the grounded coastal ice in accompanied by an endothermic process that causes refreezing as sea ice.

A buildup of snow on top of the glacier adds weight and causes strain within the ice (shear) and thus increases the amount of ice moving down slope and calving from the seaward margin of the grounded ice.

What needs to be explained is the increase in precipitation over the margins of Antarctica.

Since the interior of the continent is a desert, snowfall on the plateau can be ignored.


Full paper available here:
Antarctic precipitation and climate-change predictions: horizontal resolution and margin vs plateau issues

C. GENTHON, G. KRINNER, H. CASTEBRUNET

ABSTRACT. All climate models participating in the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, as made available by the Program for Climate Model Diagnosis and Intercomparison (PCMDI) as the Coupled Model Intercomparison Project 3 (CMIP3) archive, predict a significant surface warming of Antarctica by the end of the 21st century under a moderate (SRESA1B) greenhouse-gas scenario. All models but one predict a concurrent precipitation increase but with a large scatter of results. The models with finer horizontal resolution tend to predict a larger precipitation increase. Because modeled Antarctic surface mass balance is known to be sensitive to horizontal resolution, extrapolating predictions from the different models with respect to model resolution may provide simple yet better multi-model estimates of Antarctic precipitation change than mere averaging or even more complex approaches. Using such extrapolation, a conservative estimate of the predicted precipitation increase at the end of the 21st century is +30 kg m–2 a–1 on the grounded ice sheet, corresponding to a > 1mm a–1 sea-level rise [i.e. equivalent to 1 mm less sea level rise & acting as a negative feedback]. About three-quarters of this rise originates from the marginal regions of the Antarctic ice sheet with surface elevation below 2250 m. This is where field programs are most urgently needed to better understand and monitor accumulation at the surface of Antarctica, and to improve and verify prediction models.