Search

The Fram Strait is the only deep gateway between the Arctic and the rest of the World Ocean, and it is thus a key region to understand how the deep Arctic will evolve. However, studies and data regarding the deep ocean are scarce, making it difficult to understand its role in the climate system. Here, we analyse oceanographic data obtained close to the Fram Strait sill depth of 2500 m by two long-term mooring locations (F11 and HG-FEVI) in the Fram Strait between 2010–2023 to investigate long-term changes in the hydrographic properties. For additional context, we compile hydrographic profile data from the 1980s for the adjacent basins: the Greenland Sea and the Eurasian Basin. At mooring F11 in the western Fram Strait, we find a clear seasonality, with increased Greenland Sea Deep Water (GSDW) presence during summer and increased Eurasian Basin Deep Water (EBDW) presence during winter. Evaluating long-term changes, we find a modest temperature increase of ∼ 0.1 °C for EBDW from the 1980s. For GSDW, south of the Fram Strait, we find a strong temperature increase of ∼ 0.4–0.5 °C for the same period. The different warming rates have led to GSDW becoming warmer than EBDW since ∼ 2017–2018. This means that the Greenland Sea is no longer a heat sink for the Arctic Ocean at depth but is rather a heat source. It is therefore possible that EBDW temperatures will increase faster in the future. [ABSTRACT FROM AUTHOR]

Fram Strait is the only deep gateway between the Arctic and the rest of the World Ocean, and is thus a key region to understand how the deep Arctic will evolve. However, studies and data regarding the deep ocean are scarce, making it difficult to understand its role in the climate system. Here we analyse oceanographic data from the deep ocean from two long-term mooring locations (F11 and HG-FEVI) in Fram Strait between 2010-2023, to investigate long-term changes in the hydrographic properties. We compile hydrographic profile data since the 1980's for additional context in the upstream basins: the Greenland Sea, and the Eurasian Basin. At mooring F11 in western Fram Strait, we find a clear seasonality, with increased Greenland Sea Deep Water (GSDW) presence during summer, and increased Eurasian Basin Deep Water (EBDW) presence during winter. Evaluating long-term changes, we find a modest temperature increase of ∼ 0.1 ◦C for EBDW since the 1980's. For GSDW, south of Fram Strait, we find a strong temperature increase of ∼ 0.4-0.5 ◦C for the same period. The different warming rates have led to GSDW becoming warmer than EBDW since ∼ 2017/2018. This means that the Greenland Sea is no longer a heat sink for the Arctic Ocean at depth, but a heat source. It is therefore possible that EBDW temperatures will increase faster in the future. [ABSTRACT FROM AUTHOR]

This study quantifies the overturning circulation in the Arctic Ocean and associated heat transport (HT) and freshwater transport (FWT) from October 2004 to May 2010 based on hydrographic and current observations. Our main data source consists of 1165 moored instrument records in the four Arctic main gateways: Davis Strait, Fram Strait, Bering Strait, and the Barents Sea Opening. We employ a box inverse model to obtain mass and salt balanced velocity fields, which are then used to quantify the overturning circulation as well as HT and FWT. Atlantic Water is transformed into two different water masses in the Arctic Ocean at a rate of 4.3 Sv (1 Sv ≡ 106 m3 s−1). Combined with 0.7 Sv of Bering Strait inflow and 0.15 Sv of surface freshwater flux, 2.2 Sv flows back to the south through Davis Strait and western Fram Strait as the upper limb of the overturning circulation, and 2.9 Sv returns southward through Fram Strait as the lower limb of the overturning. The Arctic Ocean imports heat of 180 ± 57 TW (long-term mean ± standard deviation of monthly means) with a methodological uncertainty of 20 TW and exports FW of 156 ± 91 mSv with an uncertainty of 61 mSv over the 6 years with a potential offset of ∼30 mSv. The HT and FWT have large seasonalities ranging between 110 and 260 TW (maximum in winter) and between 40 and 260 mSv (maximum in winter), respectively. The obtained overturning circulation and associated HT and FWT presented here are vital information to better understand the northern extent of the Atlantic meridional overturning circulation. [ABSTRACT FROM AUTHOR]

The Fram Strait sea ice volume export 1992-2014 is derived by combining sea ice thickness from upward looking sonars (ULS) with satellite observations of sea ice drift and area. Fram Strait is the main gate for sea ice export from the Arctic. The average yearly sea ice export is 2,400 ± 640km³. The mean and modal ULS ice thickness in Fram Strait decreased by 15% and 21% per decade, respectively, during 1990-2014. Combined with sea ice drift and area this leads to a decrease of the Arctic sea ice volume export of 27 ± 2% per decade between 1992 and 2014. Thus, for the given time period, changes in sea ice export do not drive the sea ice volume decrease in the Arctic Basin. However, for individual years like 2007 and 2012 the ice export likely has contributed to the loss of summer sea ice. Combined with PIOMAS model simulation we estimate that 14% of the total Arctic sea ice volume is exported every year through Fram Strait. This fraction of the total sea ice volume exported per year does not show a trend because the Arctic Basin ice volume is decreasing at a similar rate as the Fram Strait ice volume export. Compared to ice velocities from Acoustic Doppler Current Profiler (ADCP) the satellite ice drift shows good correspondence in variability but a negative bias. Ice volume transport estimates presented here thus should be considered a conservative estimate.We show, however, that the transport estimates are not sensitive to the exact flux gate location. [ABSTRACT FROM AUTHOR]