Abstract
The water mass distribution in northern Fram Strait and over the Yermak Plateau in summer 1997 is described using CTD data from two cruises in the area. The West Spitsbergen Current was found to split, one part recirculated towards the west, while the other part, on entering the Arctic Ocean separated into two branches. The main inflow of Atlantic Water followed the Svalbard continental slope eastward, while a second, narrower, branch stayed west and north of the Yermak Plateau. The water column above the southeastern flank of the Yermak Plateau was distinctly colder and less saline than the two inflow branches. Immediately west of the outer inflow branch comparatively high temperatures in the Atlantic Layer suggested that a part of the extraordinarily warm Atlantic Water, observed in the boundary current in the Eurasian Basin in the early 1990s, was now returning, within the Eurasian Basin, toward Fram Strait. The upper layer west of the Yermak Plateau was cold, deep and comparably saline, similar to what has recently been observed in the interior Eurasian Basin. Closer to the Greenland continental slope the salinity of the upper layer became much lower, and the temperature maximum of the Atlantic Layer was occasionally below 0.5 °C, indicating water masses mainly derived from the Canadian Basin. This implies that the warm pulse of Atlantic Water had not yet made a complete circuit around the Arctic Ocean. The Atlantic Water of the West Spitsbergen Current recirculating within the strait did not extend as far towards Greenland as in the 1980s, leaving a broader passage for waters from the Atlantic and intermediate layers, exiting the Arctic Ocean. A possible interpretation is that the circulation pattern alternates between a strong recirculation of the West Spitsbergen Current in the strait, and a larger exchange of Atlantic Water between the Nordic Seas and the inner parts of the Arctic Ocean.Key words: Oceanography: general (Arctic and Antarctic oceanography; water masses) - Oceanography: physical (general circulation)
Highlights
Fram Strait has long been considered the most important communication link between the Arctic Ocean and the Nordic Seas
These originate from the colder AIW from the Greenland Sea, which interacts with the denser part of the upper Polar Deep Water (uPDW), and the Canadian Basin Deep Water (CBDW) from the north
A saline mode in the central part of the strait that lacked an upper, low salinity, Polar Mixed Layer (PML) and could be traced back to the deep winter mixed layer previously observed in the interior Eurasian Basin
Summary
Aagaard and Greisman (1975) worked out a mass budget for the Arctic Ocean, where the inow and outow through Fram Strait were balanced and, in addition to an outow of 1.8 Sv of PSW, 5.3 Sv of cooled Modi®ed Atlantic Water (MAW) were exported from the Arctic These results, and the importance of the meridional oceanic heat and freshwater transports for the climate of the Arctic, led to intensi®ed measuring activity in Fram Strait. Several complete crossings of the strait were made during MIZEX and in the years after (Quadfasel et al, 1987; Bourke et al, 1988), and the current meter observations were extended westward to the East Greenland Current (Foldvik et al, 1988) These studies showed that the recirculation of AW in Fram Strait was considerable and that the inow of AW to the Arctic Ocean was much smaller (0.6± 1.5 Sv, Aagaard and Carmack, 1989) than previously estimated. VEINS involves a simultaneous study of the exchanges through the four main passages to the Nordic Seas: the Faeroe-Shetland Channel: the Barents Sea; Fram Strait; and Denmark Strait
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