Abstract
Abrupt climate change is abundant in geological records, but
climate models rarely have been able to simulate such events in
response to realistic forcing. Here we report on a spontaneous
abrupt cooling event, lasting for more than a century, with
a temperature anomaly similar to that of the Little Ice Age. The
event was simulated in the preindustrial control run of a highresolution
climate model, without imposing external perturbations.
Initial cooling started with a period of enhanced atmospheric
blocking over the eastern subpolar gyre. In response,
a southward progression of the sea-ice margin occurred, and
the sea-level pressure anomaly was locked to the sea-ice margin
through thermal forcing. The cold-core high steered more cold air
to the area, reinforcing the sea-ice concentration anomaly east of
Greenland. The sea-ice surplus was carried southward by ocean
currents around the tip of Greenland. South of 70°N, sea ice already
started melting and the associated freshwater anomaly was
carried to the Labrador Sea, shutting off deep convection. There,
surface waters were exposed longer to atmospheric cooling and
sea surface temperature dropped, causing an even larger thermally
forced high above the Labrador Sea. In consequence, east
of Greenland, anomalous winds changed from north to south,
terminating the event with similar abruptness to its onset. Our
results imply that only climate models that possess sufficient resolution
to correctly represent atmospheric blocking, in combination
with a sensitive sea-ice model, are able to simulate this kind
of abrupt climate change.
Original language | English |
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Pages (from-to) | 19713-19718 |
Number of pages | 6 |
Journal | Proceedings of the National Academy of Sciences of the United States of America |
Volume | 110 |
Issue number | 49 |
DOIs | |
Publication status | Published - 2013 |
Keywords
- Climate modeling
- Great Salinity Anomaly
- Thermohaline circulation