Global linkages originating from decadal oceanic variability in the subpolar North Atlantic

Abstract

The anomalous decadal warming of the subpolar North Atlantic Ocean (SPNA), and the northward spreading of this warm water, has been linked to rapid Arctic sea ice loss and more frequent cold European winters. Recently, variations in this heat transport have also been reported to covary with global warming slowdown/acceleration periods via a Pacific climate response. We here examine the role of SPNA temperature variability in this Atlantic‐Pacific climate connectivity. We find that the evolution of ocean heat content anomalies from the subtropics to the subpolar region, likely due to ocean circulation changes, coincides with a basin‐wide Atlantic warming/cooling. This induces an Atlantic‐Pacific sea surface temperature seesaw, which in turn, strengthens/weakens the Walker circulation and amplifies the Pacific decadal variability that triggers pronounced global‐scale atmospheric circulation anomalies. We conclude that the decadal oceanic variability in the SPNA is an essential component of the tropical interactions between the Atlantic and Pacific Oceans.

Evolution of the Atlantic Multidecadal Variability in a Model with an Improved North Atlantic Current

“…Rather, positive heat content anomalies are found over most of the subpolar gyre region in the years around the AMV maximum. This is consistent with observations (McCarthy et al 2015;Chafik et al 2016). Note also that in the Gulf Stream region and its extension, there are negative heat content anomalies (Fig.…”

“…This point was made by Drews and Greatbatch (2016). There is, nevertheless, evidence that in the observed record, the atmospheric forcing (e.g., the NAO) has played a role in changing northward heat transport in the ocean (Eden and Jung 2001;Häkkinen et al 2011;McCarthy et al 2015;Delworth and Zeng 2016;Chafik et al 2016), influencing the observed AMV. Furthermore, the tropical part of the AMV is almost certainly generated by different mechanisms than the subpolar part (e.g., by cloud feedback) (Brown et al 2016;Yuan et al 2016).…”

Comparison of Low-Frequency Internal Climate Variability in CMIP5 Models and Observations

“…While ;75% of the HIST simulations exhibit a spectral density that is lower than observations over multidecadal time scales, the spectral density for most HIST simulations is comparable to observations on interannual time scales. Other possible mechanisms might be invoked to explain the observed-model differences; for example, too large effective horizontal diffusivity (Laepple and Huybers 2014) or teleconnections from the North Atlantic (Knight et al 2005;Zhang and Zhao 2015;Chafik et al 2016). However, this topic goes beyond the scope of the present paper.…”

Wintertime fCO2 Variability in the Subpolar North Atlantic Since 2004

“…The strength of the subpolar gyre experiences substantial interannual variability (e.g., Chafik et al, 2016;Häkkinen & Rhines, 2004;Reverdin, 2010;Tesdal et al, 2018), partly in response to the NAO, the leading mode of atmospheric variability over the subpolar North Atlantic (Hurrell & Deser, 2009). The strength of the subpolar gyre experiences substantial interannual variability (e.g., Chafik et al, 2016;Häkkinen & Rhines, 2004;Reverdin, 2010;Tesdal et al, 2018), partly in response to the NAO, the leading mode of atmospheric variability over the subpolar North Atlantic (Hurrell & Deser, 2009).…”