Variability and Redistribution of Heat in the Atlantic Water Boundary Current North of Svalbard

Renner, Angelika; Sundfjord, Arild; Janout, Markus; Ingvaldsen, Randi; Beszczyńska-Möller, Agnieszka; Pickart, Robert S.; Pérez‐Hernández, M. Dolores

doi:10.1029/2018jc013814

Cited by 74 publications

(93 citation statements)

References 62 publications

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“…Although the reasons for the WSC's winter temperature variability are ultimately outside the scope of this study, we have established a mechanism through which anomalously warm, less dense conditions in the WSC favor inflow to the Arctic Ocean via the Yermak Pass Branch. This mechanism is anecdotally supported by warm inflow pulses observed in the Arctic Circumpolar Boundary Current downstream of the Yermak Plateau (Polyakov et al, ; Renner et al, ). The WSC has earlier been warming at ~0.5 °C/decade (Beszczynska‐Möller et al, ), and the average difference in WSC temperature between pulses that took the Yermak Pass Branch and pulses that recirculated was about 0.5 °C.…”

Section: Summary and Discussionmentioning

confidence: 86%

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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Section: Summary and Discussionmentioning

confidence: 86%

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

2019

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“…Averaged over all boxes with sufficient data coverage (Boxes 4–8), the most reliable estimate of the August–September AW transport northwest and north of Svalbard is 2 Sv. Recent yearlong mooring observations in the AW boundary current at 31°E show that the current velocity increases significantly over bottom depths of around 800 m—the depth of the Yermak Pass—in fall and winter (Renner et al, ). This supports the finding of Koenig et al () that the YPB is stronger in fall and winter and that this branch provides the overall largest inflow of AW from Fram Strait to the Arctic Ocean.…”

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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“…The eastern Fram Strait and western shelf off Spitsbergen are affected by the warm and saline Atlantic water (AW), transported in the West Spitsbergen Current (WSC; e.g., Cottier et al, 2005). This current brings heat, nutrients, and carbon into the Arctic Ocean and the Svalbard area (e.g., Randelhoff et al, 2018;Renner et al, 2018). In the western part of the WSC, sea ice forms in winter and seasonal heating creates a surface layer of meltwater.…”

Section: Study Areamentioning

confidence: 99%

Net Community Production and Carbon Exchange From Winter to Summer in the Atlantic Water Inflow to the Arctic Ocean

et al. 2019

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The eastern Fram Strait and area north of Svalbard, are influenced by the inflow of warm Atlantic water, which is high in nutrients and CO 2 , influencing the carbon flux into the Arctic Ocean. However, these estimates are mainly based on summer data and there is still doubt on the size of the net ocean Arctic CO 2 sink. We use data on carbonate chemistry and nutrients from three cruises in 2014 in the CarbonBridge project (January, May, and August) and one in Fram Strait (August). We describe the seasonal variability and the major drivers explaining the inorganic carbon change (C DIC ) in the upper 50 m, such as photosynthesis (C BIO ), and air-sea CO 2 exchange (C EXCH ). Remotely sensed data describes the evolution of the bloom and net community production. The focus area encompasses the meltwater-influenced domain (MWD) along the ice edge, the Atlantic water inflow (AWD), and the West Spitsbergen shelf (SD). The C BIO total was 2.2 mol C m −2 in the MWD derived from the nitrate consumption between January and May. Between January and August, the C BIO was 3.0 mol C m −2 in the AWD, thus C BIO between May and August was 0.8 mol C m −2 . The ocean in our study area mainly acted as a CO 2 sink throughout the period. The mean CO 2 sink varied between 0.1 and 2.1 mol C m −2 in the AWD in August. By the end of August, the AWD acted as a CO 2 source of 0.7 mol C m −2 , attributed to vertical mixing of CO 2 -rich waters and contribution from respiratory CO 2 as net community production declined. The oceanic CO 2 uptake (C EXCH ) from the atmosphere had an impact on C DIC between 5 and 36%, which is of similar magnitude as the impact of the calcium carbonate (CaCO 3 , C CALC ) dissolution of 6-18%. C CALC was attributed to be caused by a combination of the sea-ice ikaite dissolution and dissolution of advected CaCO 3 shells from the south. Indications of denitrification were observed, associated with sea-ice meltwater and bottom shelf processes. C BIO played a major role (48-89%) for the impact on C DIC .

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Variability and Redistribution of Heat in the Atlantic Water Boundary Current North of Svalbard

Cited by 74 publications

References 62 publications

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

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

Net Community Production and Carbon Exchange From Winter to Summer in the Atlantic Water Inflow to the Arctic Ocean

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