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Multidecadal variability in East African hydroclimate controlled by the Indian Ocean.
MedLine Citation:
PMID:  23325220     Owner:  NLM     Status:  In-Process    
Abstract/OtherAbstract:
The recent decades-long decline in East African rainfall suggests that multidecadal variability is an important component of the climate of this vulnerable region. Prior work based on analysing the instrumental record implicates both Indian and Pacific ocean sea surface temperatures (SSTs) as possible drivers of East African multidecadal climate variability, but the short length of the instrumental record precludes a full elucidation of the underlying physical mechanisms. Here we show that on timescales beyond the decadal, the Indian Ocean drives East African rainfall variability by altering the local Walker circulation, whereas the influence of the Pacific Ocean is minimal. Our results, based on proxy indicators of relative moisture balance for the past millennium paired with long control simulations from coupled climate models, reveal that moist conditions in coastal East Africa are associated with cool SSTs (and related descending circulation) in the eastern Indian Ocean and ascending circulation over East Africa. The most prominent event identified in the proxy record--a coastal pluvial from 1680 to 1765--occurred when Indo-Pacific warm pool SSTs reached their minimum values of the past millennium. Taken together, the proxy and model evidence suggests that Indian Ocean SSTs are the primary influence on East African rainfall over multidecadal and perhaps longer timescales.
Authors:
Jessica E Tierney; Jason E Smerdon; Kevin J Anchukaitis; Richard Seager
Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  Nature     Volume:  493     ISSN:  1476-4687     ISO Abbreviation:  Nature     Publication Date:  2013 Jan 
Date Detail:
Created Date:  2013-01-17     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0410462     Medline TA:  Nature     Country:  England    
Other Details:
Languages:  eng     Pagination:  389-92     Citation Subset:  IM    
Affiliation:
Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA. tierney@whoi.edu
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