Asymmetric response of the Atlantic Meridional Ocean Circulation to
                        freshwater anomalies in a strongly-eddying global ocean model

Brunnabend, Sandra-Esther; Dijkstra, Henk A.

doi:10.1080/16000870.2017.1299283

Cited by 8 publications

(12 citation statements)

References 32 publications

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“…S1) show realistic strength and location of the Gulf Stream and other subpolar boundary currents, taking into account the resolution of the model. Previous work using the same model in a similar set-up found a well-represented distribution of currents, kinetic energy and water-mass properties at basin scale (Maltrud et al, 2010;Weijer et al, 2012;Brunnabend and Dijkstra, 2017). Moreover the modelled mixed layer depth qualitatively matches the spatial pattern derived from ARGO floats (Våge et al, 2009;, where the areas of deepest convection are found in the south-west Labrador Sea, in the Greenland Sea and around the Iceland-Scotland Ridge.…”

Section: Model Data and General Performancesupporting

confidence: 73%

Seasonal and regional variations of sinking in the subpolar North Atlantic from a high-resolution ocean model

Sayol¹,

Dijkstra²,

Katsman³

2019

Preprint

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Abstract. Previous studies have indicated that most of the net sinking associated with the downward branch of the Atlantic Meridional Overturning Circulation (AMOC) must occur near the subpolar North Atlantic boundaries. In this work we have used monthly mean fields of a high-resolution ocean model (0.1 deg at the equator) to quantify this sinking. To this end we have calculated the Eulerian net vertical transport (WΣ) from the modelled vertical velocities, its seasonal variability and its spatial distribution under repeated climatological atmospheric forcing conditions. Based on this simulation, we find that for the whole subpolar North Atlantic WΣ peaks at about −14 Sv at a depth of 1139 m, matching both the mean depth and the magnitude of the meridional transport of the AMOC at 45° N. It displays a seasonal variability of around 10 Sv. Three sinking regimes are identified according to the characteristics of the accumulated W with respect to the distance to the coast: one within the first 110 km and onto the bathymetric slope at around the peak of the boundary current speed (regime I), the second between 110 km and 290 km covering the remainder of the shelf where mesoscale eddies exchange properties (momentum, heat, mass) between the interior and the boundary (regime II), and the third sinking regime at larger distances from the coast where WΣ is mostly driven by the ocean's interior eddies (regime III). Regimes I and II accumulate ∼ 90 % of the total sinking and display smaller seasonal changes and spatial variability than regime III. We find that such a distinction in regimes is also useful to describe the characteristics of WΣ in marginal seas located far from the overflow areas, although the regime boundaries can shift a few tens of km inshore or offshore depending on the bathymetric slope and shelf width of each marginal sea. The largest contributions to the sinking come from the Labrador Sea, the Newfoundland region and the overflow regions. The magnitude, the seasonal variability and the depth at which WΣ peaks vary for each region, thus revealing a complex picture of sinking in the subpolar North Atlantic.

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Section: Model Data and General Performancesupporting

confidence: 73%

Seasonal and regional variations of sinking in the subpolar North Atlantic from a high-resolution ocean model

Sayol¹,

Dijkstra²,

Katsman³

2019

Preprint

View full text Add to dashboard Cite

show abstract

“…S1) show a realistic strength and location of the Gulf Stream and other subpolar boundary currents, taking into account the resolution of the model. Previous work using the same model in a similar setup found a well-represented distribution of currents, kinetic energy, and water-mass properties at basin scale (Maltrud et al, 2010;Weijer et al, 2012;Brunnabend and Dijkstra, 2017). Moreover, the modeled mixed layer depth qualitatively matches the spatial pattern derived from Argo floats (Våge et al, 2009;, whereby the areas of deepest convection are found in the southwest Labrador Sea, in the Greenland Sea, and around the Iceland-Scotland Ridge.…”

Section: Model Data and General Performancesupporting

confidence: 71%

“…The Atlantic Meridional Overturning Circulation (AMOC) is a fundamental component of the Earth's climate system (Lozier, 2012;Buckley and Marshall, 2016). Over the last few decades the traditional view of an ocean conveyor with an upper poleward current transporting warm waters to higher latitudes, and a downward branch with intermediate and deeper denser waters that originate in the regions of deep convection and move toward the Equator (Broecker, 1987(Broecker, , 1991, has been revised.…”

Section: Introductionmentioning

confidence: 99%

Response to Short Comment 1

Sayol¹

2019

Preprint

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“…The question of whether the AMOC can recover following a climate change-induced collapse has been addressed in a number of previous "hosing" experiments using climate models, in which a large amount of freshwater is artificially fluxed into the North Atlantic over a finite period of time (e.g., Brunnabend & Dijkstra, 2017;den Toom et al, 2014;Jackson & Vellinga, 2013;Liu et al, 2017;Mignot et al, 2007;Vellinga & Wood, 2008;Wood et al, 2003;Zhang & Delworth, 2005). Here, however, we instead address how the AMOC will respond on multidecadal timescales to a high-latitude freshwater flux (FWF) that is both modest enough to retain an active AMOC and sustained continuously in time.…”

Section: Introductionmentioning

confidence: 99%

Mechanisms and Impacts of a Partial AMOC Recovery Under Enhanced Freshwater Forcing

Thomas

Fedorov

2019

Geophysical Research Letters

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The Atlantic Meridional Overturning Circulation (AMOC) is expected to weaken in the 21st century due to increased surface buoyancy. Such AMOC changes in ocean models are often accompanied by a subsurface reduction in density. Here we perform freshwater perturbation experiments with both a 1° coupled model and an idealized zonally averaged ocean‐only model to demonstrate that slow subsurface property changes (1) introduce a negative feedback that erodes the stratification and partially reinvigorates convection and the AMOC and (2) ensure the meridional heat transport weakens less than the AMOC. In the coupled model with a 0.1‐Sv net freshwater flux introduced around Greenland, an initial 22% AMOC reduction over 40 years is followed by a recovery of almost half the lost strength after 400 years. The final heat transport, however, is weakened by only 7%. Similar responses in the idealized model demonstrate that 2‐D ocean‐only dynamics control the changes.

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Asymmetric response of the Atlantic Meridional Ocean Circulation to freshwater anomalies in a strongly-eddying global ocean model

Cited by 8 publications

References 32 publications

Seasonal and regional variations of sinking in the subpolar North Atlantic from a high-resolution ocean model

Seasonal and regional variations of sinking in the subpolar North Atlantic from a high-resolution ocean model

Response to Short Comment 1

Mechanisms and Impacts of a Partial AMOC Recovery Under Enhanced Freshwater Forcing

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