scholarly journals Decadal variability of eddy temperature fluxes in the Labrador Sea

2021 ◽  
Author(s):  
Christopher Danek ◽  
Patrick Scholz ◽  
Gerrit Lohmann
Keyword(s):  
Decadal Variability ◽  
Labrador Sea

scholarly journals The Nature of Eddy Kinetic Energy in the Labrador Sea: Different Types of Mesoscale Eddies, Their Temporal Variability, and Impact on Deep Convection

2019 ◽  
Vol 49 (8) ◽  
pp. 2075-2094 ◽  
Author(s):  
Jan K. Rieck ◽  
Claus W. Böning ◽  
Klaus Getzlaff
Keyword(s):  
Kinetic Energy ◽  
Temporal Variability ◽  
Decadal Variability ◽  
Deep Convection ◽  
Deep Ocean ◽  
Temporal Variations ◽  
Heat Fluxes ◽  
Eddy Kinetic Energy ◽  
Labrador Sea ◽  
Boundary Current

AbstractOceanic eddies are an important component in preconditioning the central Labrador Sea (LS) for deep convection and in restratifying the convected water. This study investigates the different sources and impacts of eddy kinetic energy (EKE) and its temporal variability in the LS with the help of a 52-yr-long hindcast simulation of a 1/20° ocean model. Irminger Rings (IR) are generated in the West Greenland Current (WGC) between 60° and 62°N, mainly affect preconditioning, and limit the northward extent of the convection area. The IR exhibit a seasonal cycle and decadal variations linked to the WGC strength, varying with the circulation of the subpolar gyre. The mean and temporal variations of IR generation can be attributed to changes in deep ocean baroclinic and upper-ocean barotropic instabilities at comparable magnitudes. The main source of EKE and restratification in the central LS are convective eddies (CE). They are generated by baroclinic instabilities near the bottom of the mixed layer during and after convection. The CE have a middepth core and reflect the hydrographic properties of the convected water mass with a distinct minimum in potential vorticity. Their seasonal to decadal variability is tightly connected to the local atmospheric forcing and the associated air–sea heat fluxes. A third class of eddies in the LS are the boundary current eddies shed from the Labrador Current (LC). Since they are mostly confined to the vicinity of the LC, these eddies appear to exert only minor influence on preconditioning and restratification.

The Origins of Late-Twentieth-Century Variations in the Large-Scale North Atlantic Circulation

2014 ◽  
Vol 27 (9) ◽  
pp. 3222-3247 ◽  
Author(s):  
Stephen Yeager ◽  
Gokhan Danabasoglu
Keyword(s):  
Twentieth Century ◽  
North Atlantic ◽  
Decadal Variability ◽  
Meridional Overturning Circulation ◽  
Labrador Sea ◽  
Overturning Circulation ◽  
The North ◽  
Late Twentieth ◽  
The North Atlantic ◽  
Late Twentieth Century

Abstract Surface forcing perturbation experiments are examined to identify the key forcing elements associated with late-twentieth-century interannual-to-decadal Atlantic circulation variability as simulated in an ocean–sea ice hindcast configuration of the Community Earth System Model, version 1 (CESM1). Buoyancy forcing accounts for most of the decadal variability in both the Atlantic meridional overturning circulation (AMOC) and the subpolar gyre circulation, and the key drivers of these basin-scale circulation changes are found to be the turbulent buoyancy fluxes: evaporation as well as the latent and sensible heat fluxes. These three fluxes account for almost all of the decadal AMOC variability in the North Atlantic, even when applied only over the Labrador Sea region. Year-to-year changes in surface momentum forcing explain most of the interannual AMOC variability at all latitudes as well as most of the decadal variability south of the equator. The observed strengthening of Southern Ocean westerly winds accounts for much of the simulated AMOC variability between 30°S and the equator but very little of the recent AMOC change in the North Atlantic. Ultimately, the strengthening of the North Atlantic overturning circulation between the 1970s and 1990s, which contributed to a pronounced SST increase at subpolar latitudes, is explained almost entirely by trends in the atmospheric surface state over the Labrador Sea.

scholarly journals Labrador Sea subsurface density as a precursor of multidecadal variability in the North Atlantic: a multi-model study

2021 ◽  
Vol 12 (2) ◽  
pp. 419-438
Author(s):  
Pablo Ortega ◽  
Jon I. Robson ◽  
Matthew Menary ◽  
Rowan T. Sutton ◽  
Adam Blaker ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
North Atlantic ◽  
Large Scale ◽  
Climate Model ◽  
Decadal Variability ◽  
Meridional Overturning Circulation ◽  
Labrador Sea ◽  
Western Boundary ◽  
Multidecadal Variability ◽  
Boundary Density

Abstract. The subpolar North Atlantic (SPNA) is a region with prominent decadal variability that has experienced remarkable warming and cooling trends in the last few decades. These observed trends have been preceded by slow-paced increases and decreases in the Labrador Sea density (LSD), which are thought to be a precursor of large-scale ocean circulation changes. This article analyses the interrelationships between the LSD and the wider North Atlantic across an ensemble of coupled climate model simulations. In particular, it analyses the link between subsurface density and the deep boundary density, the Atlantic Meridional Overturning Circulation (AMOC), the subpolar gyre (SPG) circulation, and the upper-ocean temperature in the eastern SPNA. All simulations exhibit considerable multidecadal variability in the LSD and the ocean circulation indices, which are found to be interrelated. LSD is strongly linked to the strength of the subpolar AMOC and gyre circulation, and it is also linked to the subtropical AMOC, although the strength of this relationship is model-dependent and affected by the inclusion of the Ekman component. The connectivity of LSD with the subtropics is found to be sensitive to different model features, including the mean density stratification in the Labrador Sea, the strength and depth of the AMOC, and the depth at which the LSD propagates southward along the western boundary. Several of these quantities can also be computed from observations, and comparison with these observation-based quantities suggests that models representing a weaker link to the subtropical AMOC might be more realistic.

scholarly journals Simulated Variability of the Circulation in the North Atlantic from 1953 to 2003

2008 ◽  
Vol 21 (19) ◽  
pp. 4919-4933 ◽  
Author(s):  
Julie Deshayes ◽  
Claude Frankignoul
Keyword(s):  
North Atlantic ◽  
Decadal Variability ◽  
Labrador Sea ◽  
Ekman Pumping ◽  
Subpolar Gyre ◽  
Dense Water ◽  
The North ◽  
Irminger Sea ◽  
Dense Water Formation ◽  
The North Atlantic

Abstract The variability of the circulation in the North Atlantic and its link with atmospheric variability are investigated in a realistic hindcast simulation from 1953 to 2003. The interannual-to-decadal variability of the subpolar gyre circulation and the Meridional Overturning Circulation (MOC) is mostly influenced by the North Atlantic Oscillation (NAO). Both circulations intensified from the early 1970s to the mid-1990s and then decreased. The monthly variability of both circulations reflects the fast barotropic adjustment to NAO-related Ekman pumping anomalies, while the interannual-to-decadal variability is due to the baroclinic adjustment to Ekman pumping, buoyancy forcing, and dense water formation, consistent with previous studies. An original characteristic of the oceanic response to NAO is presented that relates to the spatial patterns of buoyancy and wind forcing over the North Atlantic. Anomalous Ekman pumping associated with a positive NAO phase first induces a decrease of the southern subpolar gyre strength and an intensification of the northern subpolar gyre. The latter is reinforced by buoyancy loss and dense water formation in the Irminger Sea, where the cyclonic circulation increases 1–2 yr after the positive NAO phase. Increased buoyancy loss also occurs in the Labrador Sea, but because of the early decrease of the southern subpolar gyre strength, the intensification of the cyclonic circulation is delayed. Hence the subpolar gyre and the MOC start increasing in the Irminger Sea, while in the Labrador Sea the circulation at depth leads its surface counterpart. In this simulation where the transport of dense water through the North Atlantic sills is underestimated, the MOC variability is well represented by a simple integrator of convection in the Irminger Sea, which fits better than a direct integration of NAO forcing.

scholarly journals Interannual to decadal variability of outflow from the Labrador Sea

2010 ◽  
Vol 37 (24) ◽  
pp. n/a-n/a ◽  
Author(s):  
Jürgen Fischer ◽  
Martin Visbeck ◽  
Rainer Zantopp ◽  
Nuno Nunes
Keyword(s):  
Decadal Variability ◽  
Labrador Sea

scholarly journals Labrador Sea sub-surface density as a precursor of multi-decadal variability in the North Atlantic: a multi-model study

2020 ◽  
Author(s):  
Pablo Ortega ◽  
Jon I. Robson ◽  
Matthew Menary ◽  
Rowan T. Sutton ◽  
Adam Blaker ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
North Atlantic ◽  
Large Scale ◽  
Climate Model ◽  
Decadal Variability ◽  
Meridional Overturning Circulation ◽  
Labrador Sea ◽  
Western Boundary ◽  
Overturning Circulation ◽  
Boundary Density

Abstract. The Subpolar North Atlantic (SPNA) is a region with prominent decadal variability that has experienced remarkable warming and cooling trends in the last few decades. These observed trends have been preceded by slow-paced increases and decreases in the Labrador Sea density (LSD), which are thought to be a precursor of large scale ocean circulation changes. This article analyses the inter-relationships between the LSD and the wider North Atlantic across an ensemble of coupled climate model simulations. In particular, it analyses the link between subsurface density and the deep boundary density, the Atlantic Meridional Overturning Circulation (AMOC), the Subpolar Gyre (SPG) circulation, and the upper ocean temperature in the eastern SPNA. All simulations exhibit considerable multidecadal variability in the LSD and the ocean circulation indices, which are found to be interrelated. LSD is strongly linked with the strength of subpolar AMOC and gyre circulation, and is also linked with the subtropical AMOC, although the strength of this relationship is model dependent. The connectivity of LSD with the subtropics is found to be sensitive to different model features, including: the mean density stratification in the Labrador Sea; the strength and depth of the AMOC; and the depth at which the LSD propagates southward along the western boundary. Several of these quantities can also be computed from observations, and comparison with these observation-based quantities suggests that models representing a weaker link with the subtropical AMOC may be more realistic. This would imply that RAPID AMOC measurements might not be adequate to represent decadal to multidecadal changes in the subpolar overturning circulation.

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