Arctic warming through the Fram Strait: Oceanic heat transport from 3 years of measurements

Abstract

We present estimates of volume and heat transport through Fram Strait for the period 1997 to 2000 from data of moored instruments. The annual mean volume transports at 78°55′N were between 9 2 and 10 1 Sv northward and 13 2 and 12 1 Sv southward with a net transport between 4 2 and 2 2 Sv to the south. The temperature of the northward flow of Atlantic Water had a strong seasonality with a minimum in winter. Nevertheless, the northward heat transport was highest in winter caused by the winter maximum of northward volume transport. Between 1997 and 1999, the annual mean net heat transport across 78°55′N increased from 16 12 to 41 5 TW. This resulted from a very strong increase in heat transport in the West Spitsbergen Current (mean annual values from 28 5 to 44 6 TW and to 46 5 TW in 99/00) which was not compensated by an equivalent signal in the southward flow. The heat transport to the south remained constant within error limitations. Only half of the heat flux increase in the West Spitsbergen Current was due to a higher temperature; half of it was due to a stronger flow. A similar increase as observed between 1997 and 2000 would have been sufficient to explain the warming of intermediate layers in the Eurasian Arctic observed in the early 1990s. Consequently, we suggest that a warming signal from the late 1990s is presently spreading in the interior Arctic Ocean.

Recent advances in understanding the Arctic climate system state and change from a sea ice perspective: a review

“…An overall increase in northward flowing Fram Strait temperature and transports was found after 1999 and 2004 (Schauer et al, 2004, BeszcynskaMöller et al, 2012). An indication of increased inflow was already seen in the early 1990s when Atlantic water was observed in the southern Makarov Basin, which was previously dominated by Pacific waters (McLaughlin et al, 1996;Smith et al, 1999).…”

“…This Atlantic water returns in parts (2 Sv), due to a local recirculation (Aagaard and Greisman, 1975;Marnela et al, 2013). The remaining part, ca 2-4 Sv (Schauer et al, 2008, andBeszcynska-Möller et al, 2012) of the WSC proceeds eastwards along the continental slope in two different branches (Schauer et al, 2004). Little is known about its further processing by turbulent eddies.…”

Fluxes and fate of dissolved methane released at the seafloor at the landward limit of the gas hydrate stability zone offshore western Svalbard

“…As bottom water currents in this area are fast, the methane released at the seafloor is rapidly flushed away from its source in the northward-flowing WSC. Monthly mean current velocity in the WSC offshore western Svalbard is up to $24 cm s 21 on the upper continental slope [Fahrbach et al, 2001;Schauer et al, 2004], with wintertime peaks exceeding 50 cm s 21 . The net effects of tidal displacement are expected to be minor, as neither methane concentrations nor other bottom water properties were related to the tidal phase during sampling.…”

Current estimates of freshwater flux through Arctic and subarctic seas

“…The export of Atlantic water, salinity 35.0, to the Arctic Ocean via Fram Strait has recently been estimated as 4 Sv from the VEINS/ASOF observations (see e.g. Schauer et al, 2004). The exchanges of the deeper waters likely involve a large recirculation but at least some Arctic Intermediate Water and some Nordic Seas deep water pass north of the Yermak Plateau into the Sofia Deep and thus into the Nansen Basin (Rudels et al, 2000;Rudels et al, 2005).…”