Atmospheric extremes caused high oceanward sea surface slope triggering the biggest calving event in more than 50 years at the Amery Ice Shelf
<p>Ice shelf instability is one of the main sources of uncertainty in Antarctica's contribution to future sea level rise. Calving events play a crucial role in ice shelf weakening but remain unpredictable, and their governing processes are still poorly understood. In this study, we analyz...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2021-05-01
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| Series: | The Cryosphere |
| Online Access: | https://tc.copernicus.org/articles/15/2147/2021/tc-15-2147-2021.pdf |
| Summary: | <p>Ice shelf instability is one of the main sources of uncertainty in
Antarctica's contribution to future sea level rise. Calving events play a
crucial role in ice shelf weakening but remain unpredictable, and their
governing processes are still poorly understood. In this study, we analyze
the unexpected September 2019 calving event from the Amery Ice Shelf, the
largest since 1963 and which occurred almost a decade earlier than expected,
to better understand the role of the atmosphere in calving. We find that
atmospheric extremes provided a deterministic role in this event. A series
of anomalously deep and stationary explosive twin polar cyclones over the
Cooperation and Davis seas generated tides and wind-driven ocean slope,
leading to fracture amplification along the pre-existing rift and
ultimately calving of the massive iceberg. The calving was triggered by high
oceanward sea surface slopes produced by the storms. The observed
record-anomalous atmospheric conditions were promoted by blocking ridges and
Antarctic-wide anomalous poleward transport of heat and moisture. Blocking
highs helped in (i) directing moist and warm air masses towards the ice
shelf and (ii) maintaining the observed extreme cyclones stationary at
the front of the ice shelf for several days. Accumulation of cold air over
the ice sheet, due to the blocking highs, led to the formation of an intense
cold high pressure over the ice sheet, which helped fuel sustained
anomalously deep cyclones via increased baroclinicity. Our results stress
the importance of atmospheric extremes in ice shelf dynamics via tides and
sea surface slope and its need to be accounted for when considering
Antarctic ice shelf variability and contribution to sea level, especially
given that more of these extremes are predicted under a warmer climate.</p> |
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| ISSN: | 1994-0416 1994-0424 |