Seasonal and Mesoscale Variability of the Two Atlantic Water Recirculation Pathways in Fram Strait
Creators: name: Hofmann, Zerlina
name: Von Appen, Wilken‐Jon
name: Wekerle, Claudia
Publisher: name: FID GEO
Year: 2021

description: Atlantic Water (AW), which is transported northward by the West Spitsbergen Current (WSC), partly recirculates (i.e., turns westward) in Fram Strait. This determines how much heat and salt reaches the Arctic Ocean, and how much joins the East Greenland Current on its southward path. We describe the AW recirculation's location, seasonality, and mesoscale variability by analyzing the first observations from moored instruments at five latitudes in central Fram Strait, spanning a period from August 2016 to July 2018. We observe recirculation on the prime meridian at 78°50’N and 80°10’N, respectively south and north of the Molloy Hole, and no recirculation further south at 78°10’N and further north at 80°50’N. At a fifth mooring location northwest of the Molloy Hole at 79°30’N, we observe some influence of the two recirculation pathways. The southern recirculation is observed as a continuous westward flow that carries AW throughout the year, though it may be subject to broadening and narrowing. It is affected by eddies in spring, likely due to the seasonality of mesoscale instability in the WSC. The northern recirculation is observed solely as passing eddies on the prime meridian, which are strongest during late autumn and winter, and absent during summer. This seasonality is likely affected both by the conditions set by the WSC and by the sea ice. Open ocean eddies originating from the WSC interact with the sea ice edge when they subduct below the fresher, colder water.
description: Plain Language Summary: West of Spitsbergen, the so‐called West Spitsbergen Current (WSC) carries relatively warm water towards the Arctic Ocean. Part of this water turns westward before it reaches the Arctic Ocean. Another current transports it back south along the Greenland shelf. We look at observations of temperature, salinity, and flow velocity from two years in the region. We find that the warm water flows westwards at two latitudes. At 78°50’N it flows westwards throughout the year, but is affected by eddies in the ocean during spring. These eddies also carry warm water westwards and likely originate from the WSC. At 80°10’N, the warm water passes only over periods of a few days, and only during late autumn, winter, and spring. That means that we do not observe the warm water flowing westwards at this latitude, but only eddies that carry it westwards. These eddies also originate from the WSC, and their properties likely change, when they meet the ice edge and have to push underneath.
description: Key Points: We present the first multi‐year mooring‐based observations of the Atlantic Water recirculation at the prime meridian. At 78°50’N we observe a continuous westward flow, present throughout the year and most affected by eddies in spring. At 80°10′N we only observe passing eddies, which are strongest during late autumn and winter, and absent during summer.
description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
description: Helmholtz Infrastructure Initiative FRAM