Role of Greenland Sea Gyre Circulation on Atlantic Water Temperature Variability in the Fram Strait

Chatterjee, Sourav; Raj, Roshin P.; Bertino, Laurent; Skagseth, Øystein; Ravichandran, M.; Johannessen, Ola M.

doi:10.1029/2018gl079174

Cited by 35 publications

(55 citation statements)

References 41 publications

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“…The barotropic stream function is here defined as

ψ = - \int_{east}^{west} v d x, u = \frac{- \partial ψ}{\partial y} & v = \frac{\partial ψ}{\partial x},

where u and v are the depth‐integrated currents in the x and y directions. As previously shown by Aagaard (), Nøst and Isachsen (), and Chatterjee et al (), the leading mode features a barotropic cyclonic circulation in the Nordic Seas. Consequently, the area‐average barotropic stream function over the central Nordic Seas (bounded by 66–76° N, 15° W to 10° E) can be used as an indicator of the strength of the Nordic Seas gyre circulation.…”

Section: Resultsmentioning

confidence: 99%

Arctic Ocean Response to Greenland Sea Wind Anomalies in a Suite of Model Simulations

et al. 2019

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Multimodel Arctic Ocean “climate response function” experiments are analyzed in order to explore the effects of anomalous wind forcing over the Greenland Sea (GS) on poleward ocean heat transport, Atlantic Water (AW) pathways, and the extent of Arctic sea ice. Particular emphasis is placed on the sensitivity of the AW circulation to anomalously strong or weak GS winds in relation to natural variability, the latter manifested as part of the North Atlantic Oscillation. We find that anomalously strong (weak) GS wind forcing, comparable in strength to a strong positive (negative) North Atlantic Oscillation index, results in an intensification (weakening) of the poleward AW flow, extending from south of the North Atlantic Subpolar Gyre, through the Nordic Seas, and all the way into the Canadian Basin. Reconstructions made utilizing the calculated climate response functions explain ∼50% of the simulated AW flow variance; this is the proportion of variability that can be explained by GS wind forcing. In the Barents and Kara Seas, there is a clear relationship between the wind‐driven anomalous AW inflow and the sea ice extent. Most of the anomalous AW heat is lost to the atmosphere, and loss of sea ice in the Barents Sea results in even more heat loss to the atmosphere, and thus effective ocean cooling. Release of passive tracers in a subset of the suite of models reveals differences in circulation patterns and shows that the flow of AW in the Arctic Ocean is highly dependent on the wind stress in the Nordic Seas.

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“…The barotropic stream function is here defined as

ψ = - \int_{east}^{west} v d x, u = \frac{- \partial ψ}{\partial y} & v = \frac{\partial ψ}{\partial x},

Section: Resultsmentioning

confidence: 99%

Arctic Ocean Response to Greenland Sea Wind Anomalies in a Suite of Model Simulations

et al. 2019

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“…Therefore, the warmer‐than‐expected WSC cannot be explained by regional air temperatures. It could be instead that the WSC's faster‐than‐expected speed during Yermak Pass Branch pulses reduced atmospheric cooling and mixing with surrounding water masses (Chatterjee et al, ). Chatterjee et al () found that warm WSC anomalies were associated with a faster current resulting from anomalously positive wind stress curl over the Nordic Seas and a stronger Greenland Sea Gyre.…”

Section: Summary and Discussionmentioning

confidence: 99%

“…It could be instead that the WSC's faster‐than‐expected speed during Yermak Pass Branch pulses reduced atmospheric cooling and mixing with surrounding water masses (Chatterjee et al, ). Chatterjee et al () found that warm WSC anomalies were associated with a faster current resulting from anomalously positive wind stress curl over the Nordic Seas and a stronger Greenland Sea Gyre. The most common atmospheric types during Yermak Pass Branch pulses were cyclonic systems bringing wind from the E‐NE‐N to Svalbard, matching the signature of a cyclone moving from the Greenland Sea to the Barents Sea.…”

Section: Summary and Discussionmentioning

confidence: 99%

How the Yermak Pass Branch Regulates Atlantic Water Inflow to the Arctic Ocean

2019

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The Yermak Plateau is a topographic obstacle which warm water in the West Spitsbergen Current (Atlantic Water) must pass in order to enter the Arctic Ocean. The main route for Atlantic Water to cross the Yermak Plateau is the Yermak Pass Branch, a winter-intensified pathway characterized by pulse-like high-transport events. Here we use an eddy-resolving sea ice and ocean model to investigate oceanographic conditions that promote flow over the Yermak Plateau. Yermak Pass Branch pulses were associated with a warmer, faster West Spitsbergen Current; these conditions created a region of high offshore Ertel potential vorticity upstream of the plateau. As potential vorticity was low in the current itself, this region of high offshore potential vorticity acted as a barrier that guided flow onto the plateau. During times of enhanced recirculation in Fram Strait, this offshore potential vorticity barrier was weaker, likely allowing the current to deflect away from the continental slope. Through this potential vorticity mechanism, the upstream hydrography of the West Spitsbergen Current can determine how much Atlantic Water crosses the plateau, implying that less dense West Spitsbergen Current core water promotes more inflow into the Arctic Ocean and less recirculation in Fram Strait. Plain Language SummaryWe used an ocean and sea ice model to study a current (the West Spitsbergen Current) which carries relatively warm water to the Arctic Ocean. In a key gateway region called Fram Strait, just before the current enters the Arctic Ocean, some of the water takes a shortcut and returns south along Greenland. The rest flows over a shallower area called the Yermak Plateau. Our goal was to learn what pushed pulses of wintertime flow through one pathway or the other. We found that flow was routed into the Arctic Ocean when the current was warmer and faster. This is because the current must conserve a quantity called potential vorticity, and when the current was warmer and faster, the potential vorticity alongside the current increased. This potential vorticity "wall" guided the flow to enter the Arctic Ocean. This means that if the temperature of the current flowing toward the Arctic Ocean increases, the amount of warm water that actually enters the Arctic Ocean could also increase. CREWS ET AL.

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“…We found that the circulation patterns from high‐resolution models (Hattermann et al, ; Koenig et al, ; Wekerle et al, ) agree well with our observations, especially in pointing out the importance of the YPB for AW transport into the Arctic. The strength and pathways of AW flow around Svalbard are forced by multiple factors: the large‐scale oceanic and atmospheric circulation system (Chatterjee et al, ; Kawasaki & Hasumi, ), the local wind field (Inall et al, ), topography, instabilities, and eddies (Hattermann et al, ; von Appen et al, ; Wekerle et al, ). The average large‐scale AW flow is confined to slopes, plateaus, and trenches, implying that the bottom topography is a major controlling factor.…”

Section: Discussionmentioning

confidence: 99%

“…The average large‐scale AW flow is confined to slopes, plateaus, and trenches, implying that the bottom topography is a major controlling factor. However, the strength of the three AW branches likely varies with time and season and is related to external forcing such as the strength of the North Atlantic gyres, the wind field, and the instability of the WSC and the rate of eddy formation (Chatterjee et al, ; Kawasaki & Hasumi, ; Wekerle et al, ).…”

Section: Discussionmentioning

confidence: 99%

Atlantic Water Pathways Along the North‐Western Svalbard Shelf Mapped Using Vessel‐Mounted Current Profilers

et al. 2019

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A large amount of warm Atlantic water (AW) enters the Arctic as a boundary current through Fram Strait (West Spitsbergen Current [WSC]) and is the major oceanic heat source to the Arctic Ocean. Along the north‐western Svalbard shelf, the WSC splits into the shallow Svalbard Branch, the Yermak Branch that follows the slope of the Yermak Plateau, and the Yermak Pass Branch flowing across the plateau. The WSC has previously been studied using moorings, dedicated oceanographic transects, and models. In this study, we mapped the circulation patterns and AW flow around Svalbard using Vessel‐Mounted Acoustic Doppler Current Profiler data from multiple surveys during four consecutive summers (2014–2017). Despite the scattered nature of this compiled data set, persistent circulation patterns could be discerned. Spatial interpolation showed a meandering boundary current west of Svalbard and a more homogeneous AW flow, centered around the 1,000‐m isobath north of Svalbard. In all summers, we observed a northward jet between 79 and 80°N and the 1,000‐ and 500‐m isobaths, before the WSC divided into the three branches. North of Svalbard, the shallow Svalbard Branch reunited with the Yermak Pass Branch between 10 and 15°E and a part of the AW circulated within Hinlopen Trench. The calculated volume transport of 2 Sv in the upper 500 m compares well with model results and previous observations. Our results further show that the Yermak Pass Branch can be as important as the Svalbard Branch in transporting AW across the Yermak Plateau during summer.

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Role of Greenland Sea Gyre Circulation on Atlantic Water Temperature Variability in the Fram Strait

Cited by 35 publications

References 41 publications

Arctic Ocean Response to Greenland Sea Wind Anomalies in a Suite of Model Simulations

Arctic Ocean Response to Greenland Sea Wind Anomalies in a Suite of Model Simulations

How the Yermak Pass Branch Regulates Atlantic Water Inflow to the Arctic Ocean

Atlantic Water Pathways Along the North‐Western Svalbard Shelf Mapped Using Vessel‐Mounted Current Profilers

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