What are the differences between 4.2ka and 8.2ka climate events?
Abstract
The spatial patterns of global temperature and precipitation changes, as well as corresponding large-scale circulation patterns during the 8.2ka event and 4.2ka event are compared through a group of transient simulations over the last 21,000 years using CCSM3. Both events are characterized as significant temperature decreases over the northern hemisphere with the most significant decreases locating the Greenland Island. Significant precipitation decreases also occur over the northern hemisphere, especially over the Eurasia and Asian summer monsoon region, indicating weaker Asian summer monsoon. Anomalous sea surface temperature (SST) over the northern Atlantic are related to the both events. Composite analysis and rotate empirical orthogonal function (REOF) analysis show that SST changes during 8.2ka event are similar to the Atlantic Multi-Decadal Oscillation (AMO) pattern, however, SST changes during 4.2ka event mainly locate over the northern part of the northern Atlantic. For the external forcing for these SST patterns, 8.2ka event is widely consented to be caused by fresh water injection into northern Atlantic confirmed through a meltwater forcing sensitivity experiment, while, the potential external forcing (e.g., solar radiation, volcanic eruptions) contributing to 4.2ka event still need further examinations. The preliminary study on these extreme climate events shows that climate model has strong capabilities on retrieving the physical mechanisms resulting these events. The collaborations between modelers and other communities, such as archaeologists and proxy reconstructionists, are highly necessary to further investigate the ultimate reasons behind these events.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMPP43E1974N
- Keywords:
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- 4901 Abrupt/rapid climate change;
- PALEOCEANOGRAPHYDE: 4914 Continental climate records;
- PALEOCEANOGRAPHYDE: 4928 Global climate models;
- PALEOCEANOGRAPHYDE: 4962 Thermohaline;
- PALEOCEANOGRAPHY