Mechanisms underlying recent decadal changes in subpolar North Atlantic Ocean heat content. Issue 9 (8th September 2017)

• Record Type: Journal Article
• Authors: Piecuch, Christopher G.; Ponte, Rui M.; Little, Christopher M.; Buckley, Martha W.; Fukumori, Ichiro
• Is Part Of: Journal of geophysical research. Volume 122:Issue 9(2017)
• Page Start: 7181
• Page End: 7197
• Publication Date: 2017-09-08
• Subjects: decadal variability -- heat content -- Sverdrup balance -- overturning circulation -- Atlantic multidecadal variability -- ocean state estimation; Oceanography -- Periodicals; 551.4605
• DOI: 10.1002/2017JC012845
• Languages: English
• ISSNs: 2169-9275

Abstract

Abstract: The subpolar North Atlantic (SPNA) is subject to strong decadal variability, with implications for surface climate and its predictability. In 2004–2005, SPNA decadal upper ocean and sea‐surface temperature trends reversed from warming during 1994–2004 to cooling over 2005–2015. This recent decadal trend reversal in SPNA ocean heat content (OHC) is studied using a physically consistent, observationally constrained global ocean state estimate covering 1992–2015. The estimate's physical consistency facilitates quantitative causal attribution of ocean variations. Closed heat budget diagnostics reveal that the SPNA OHC trend reversal is the result of heat advection by midlatitude ocean circulation. Kinematic decompositions reveal that changes in the deep and intermediate vertical overturning circulation cannot account for the trend reversal, but rather ocean heat transports by horizontal gyre circulations render the primary contributions. The shift in horizontal gyre advection reflects anomalous circulation acting on the mean temperature gradients. Maximum covariance analysis (MCA) reveals strong covariation between the anomalous horizontal gyre circulation and variations in the local wind stress curl, suggestive of a Sverdrup response. Results have implications for decadal predictability. Key Points: Recent decadal changes in subpolar North Atlantic heat content are due to advective heat flux convergences by midlatitude ocean transports Horizontal gyre circulations contribute more to advective convergences than vertical overturning circulations at 46°N Anomalous gyre circulation strongly covaries with local wind stress curl, suggesting a role for Sverdrup dynamics