On the mechanisms behind decadal heat content changes in the eastern subpolar gyre

  • Desbruyères D
  • Mercier H
  • Thierry V
  • 28

    Readers

    Mendeley users who have this article in their library.
  • 7

    Citations

    Citations of this article.

Abstract

Historical and modern hydrographic data show substantial decadal variability in the heat content (HC) of the eastern subpolar North Atlantic. Those changes are here investigated in an eddy-permitting simulation (ORCA025-G70) forced by reanalysis products for the period 1965-2004. The observed and simulated decadal signal is characterized by a strong cooling in the 1960s and 1970s, a period of minor changes in the 1980s, and a strong warming in the 1990s and 2000s. A heat budget calculation is performed within a box bounded by the Greenland-Scotland sills and the Cape Farewell (Greenland)-Portugal A25-Ovide section. The decadal variability of HC is mainly governed by the integrated effect of anomalous oceanic heat transport across A25-Ovide (HTA25), with local air-sea heat fluxes playing a damping role. The impact of temperature changes acting upon the mean oceanic circulation is shown to dominate the long-term behavior of HTA25. Through Lagrangian experiments, we show that temperature anomalies advected by the mean circulation across A25-Ovide are mostly created by the gyre circulation anomalies upstream of A25-Ovide and the associated changes in the relative proportion of cold subpolar and warm subtropical waters feeding the northern and southern branches of the North Atlantic Current. These temperature anomalies induce large-scale changes in the pycnocline slope east of Reykjanes Ridge along A25-Ovide: when the NAC is relatively cold (warm), the main pycnocline moves upward (downward) in the Iceland Basin and on top of Reykjanes Ridge, thereby increasing (decreasing) the pycnocline slope. The resulting velocity anomalies lead to heat transport changes that strongly oppose the thermally-driven heat transport anomalies.

Get free article suggestions today

Mendeley saves you time finding and organizing research

Sign up here
Already have an account ?Sign in

Find this document

Authors

Cite this document

Choose a citation style from the tabs below

Save time finding and organizing research with Mendeley

Sign up for free