Shifts of the Recirculation Pathways in Central Fram Strait Drive Atlantic Intermediate Water Variability on Northeast Greenland Shelf

• Published in: Journal of geophysical research. Oceans Vol. 128; no. 10
• Main Authors: McPherson, R. A., Wekerle, C., Kanzow, T.
• Format: Journal Article
• Language: English
• Published: Washington Blackwell Publishing Ltd 01-10-2023
• Subjects: Anomalies; Atmospheric circulation; Atmospheric forcing; Continental shelves; Geophysics; Glaciation; Glacier melting; Glaciers; Greenland ice sheet; Heat transport; Ice sheets; Intermediate water; Intermediate water masses; Melting; Ocean currents; Ocean temperature; Oceans; Seasonal variability; Shelf dynamics; Shelf edge; Straits; Strengthening; Temperature; Temperature variability; Upstream; Variability; Warm water; Water circulation; Water flow; Water temperature; West Spitsbergen Current; Wind; Winds; Arctic Ocean; Barents Sea; Fram Strait; Greenland
• DOI: 10.1029/2023JC019915
• EISSN: 2169-9291
• ISSN: 2169-9275

Increased oceanic heat transport plays a key role in the accelerated mass loss of Greenland's marine‐terminating glaciers. The melt rate of major glaciers in Northeast Greenland (NEG) is controlled by ocean variability, in particular warm Atlantic Intermediate Water (AIW), on the continental shelf. A high‐resolution configuration of the ocean sea‐ice model FESOM2.1 is assessed at local and regional scales, and used to investigate the drivers of AIW temperature variability on the NEG continental shelf. The seasonal to decadal variability of AIW is characterized, featuring both pronounced interannual fluctuations and a long‐term warming trend. A major source of AIW is Atlantic Water (AW) originating from the West Spitsbergen Current that recirculates in Fram Strait. AW anomalies are advected westwards and partly control the AIW temperatures on the continental shelf. Increased AIW temperatures are also connected to pronounced northern and central branches of recirculating AW in Fram Strait, and enhanced AW temperatures more regionally. The strengthening of the pathways brings more warmer AIW onto the northern part of the NEG continental shelf. There, it circulates anti‐cyclonically and results in shelf‐wide warming. Regional atmospheric forcing is connected to the changes in the AW circulation. The strengthening of the northern AW branches is likely caused by anticyclonic wind anomalies over the Barents Sea that drive an enhanced northward AW transport in Fram Strait. Thus, controlled by a combination of both upstream and regionally forced circulation conditions, the changes in local AIW temperatures may also affect the oceanic heat transport reaching the Central Arctic Ocean.
The Greenland Ice Sheet has been melting at faster rates in the last two decades, likely due to rising ocean temperatures. Warm water found below the glaciers in Northeast Greenland controls the submarine melting. Changes in the temperature of the water are connected to ocean currents on the continental shelf of Northeast Greenland and in Fram Strait. The warm water found under the glaciers originates from the West Spitsbergen Current (WSC), over several hundred kilometers away, which carries warm water northwards within the Arctic Ocean. Part of the current turns westwards and transports the warm water toward Greenland. The changes in the strength of the westward flow are connected with particular wind patterns in the Barents Sea, as the wind forcing impacts the northward transport of the warm water in the WSC. This means that more warm water flows across the continental shelf edge at higher latitudes so there is more warm water circulating on the continental shelf itself. The circulation guides this warm water through a deep channel toward the glaciers. Therefore, the variability of the water temperature below the glaciers in Northeast Greenland is controlled by both regional winds and changes in the upstream ocean currents.
Warm temperature anomalies in the West Spitsbergen Current partly control Atlantic Water temperatures on the Northeast Greenland continental shelf
Pronounced northern recirculation branches transport more Atlantic Water across Fram Strait to the northern shelf where it circulates
Anomalous anticyclonic winds over the Barents Sea drive the enhanced recirculation of more northern Atlantic Water pathways