The ice is melting everywhere.
In Antarctica, the ice shelves extending over the ocean have been thinning at a rapid pace, likely due to warmer ocean waters undercutting them. This could lead to ice from the interior flowing faster to the sea, resulting in thinning of the whole ice cap. But this relationship has not be established, nor is it clear how much of overall ice changes might be due to such effects. In addition, it has not been known how rapidly any effect propagate inland, i.e., how fast the rest of the ice responds to the loss of sea ice.
This winter, researchers from California and Northumbria report a new study of the whole of Antarctica uses improved measurements of ice thickness and movement from IceSat-2 and earlier satellites . They developed a model of the complex processes that occur at the grounding lines of glaciers, which are the product of “an intricate interplay between several opposing processes”.
The model agrees with the observed distribution of ice losses around Antarctica. Furthermore, the model suggests that the effects are essentially instantaneous, i.e., thinning sea ice causes increased flow upstream with little delay. This model only includes the effects of thinning at grounding lines, but this seems to be a major contributor to the overall mass loss. These changes at grounding lines are due to warming ocean waters.
“We find that the magnitude and spatial variability of modelled changes are in good agreement with observations, suggesting that thinning ice shelves have driven a substantial portion of the recent ice-loss of the Antarctic ice sheet”
Both the data and the models have limitations, so this finding will need to be confirmed with further study and better data. The data is still pretty sparse, and there are plenty of other factors that may be involved (such as wind, cloud cover, and precipitation patterns).
But if these findings stand up, we can expect to see further rapid ice loss across all of Antarctica, with much faster losses in places where warm ocean waters are thinning the sea ice.
- G. Hilmar Gudmundsson, Fernando S. Paolo, Susheel Adusumilli, and Helen A. Fricker, Instantaneous Antarctic ice-sheet mass loss driven by thinning ice shelves. Geophysical Research Letters, n/a (n/a) 2019/11/20 2019. https://doi.org/10.1029/2019GL085027