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Title: Mechanisms of Low-Frequency Variability in North Atlantic Ocean Heat Transport and AMOC
Abstract Ocean heat transport (OHT) plays a key role in climate and its variability. Here, we identify modes of low-frequency North Atlantic OHT variability by applying a low-frequency component analysis (LFCA) to output from three global climate models. The first low-frequency component (LFC), computed using this method, is an index of OHT variability that maximizes the ratio of low-frequency variance (occurring at decadal and longer timescales) to total variance. Lead-lag regressions of atmospheric and ocean variables onto the LFC timeseries illuminate the dominant mechanisms controlling low-frequency OHT variability. Anomalous northwesterly winds from eastern North America over the North Atlantic act to increase upper ocean density in the Labrador Sea region, enhancing deep convection, which later increases OHT via changes in the strength of the Atlantic Meridional Overturning Circulation (AMOC). The strengthened AMOC carries warm, salty water into the subpolar gyre, reducing deep convection and weakening AMOC and OHT. This mechanism, where changes in AMOC and OHT are driven primarily by changes in Labrador Sea deep convection, holds not only in models where the climatological (i.e., time-mean) deep convection is concentrated in the Labrador Sea, but also in models where the climatological deep convection is concentrated in the Greenland-Iceland-Norwegian (GIN) Seas more » or the Irminger and Iceland Basins. These results suggest that despite recent observational evidence suggesting that the Labrador Sea plays a minor role in driving the climatological AMOC, the Labrador Sea may still play an important role in driving low-frequency variability in AMOC and OHT. « less
Authors:
; ; ; ;
Award ID(s):
1850900 1929775
Publication Date:
NSF-PAR ID:
10230743
Journal Name:
Journal of Climate
Page Range or eLocation-ID:
1 to 68
ISSN:
0894-8755
Sponsoring Org:
National Science Foundation
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