Explaining the intrusion of warm water in West Spitsbergen fjords

Explaining the intrusion of warm water in West Spitsbergen fjords

Top image: Large heat exhcange between open water and the atmosphere in the Isfjorden system due to a higher than normal seawater temperature. Photo: Frank Nilsen/UNIS.

The ocean monitoring program in Isfjorden, Kongsfjorden and the shelf areas along West Spitsbergen have shown that during the winter 2005/06, periods of sustained northerly winds generated cross-shelf exchange causing extensive flooding of the coastal waters with warm Atlantic Water from the West Spitsbergen Current (the last leg of the Gulf Current system). The seawater winter temperature of the West Spitsbergen Shelf and fjords reverted to that typically of fall, interrupting the normal cycle of ice formation in the region.

1 June 2007
Text: Frank Nilsen, UNIS Associate Professor in Oceanography

Scientists from UNIS, SAMS (Scottish Association for Marine Science), NP and GFI (The Geophysical Institute, University of Bergen) are running a monitoring program in Isfjorden, Kongsfjorden and the shelf areas along West Spitsbergen by using ocean current meter instruments and instruments for observing the temperature and salinity changes.

Data have been collected since 2001 and the winter data from 2006 clearly showed a change in the water masses along West Spitsbergen. Data analysis revealed that during the Arctic winter of 2005—2006, periods of sustained winds over Svalbard’s West Spitsbergen Shelf dynamically generated upwelling and cross-shelf exchanges, causing extensive flooding of the typically cold coastal waters with warm Atlantic water from the West Spitsbergen Current.

The winter temperature of water on the West Spitsbergen Shelf and in the fjords then reverted to that typical of fall, interrupting the normal cycle of sea ice formation in the region.

In January 2006 warm air was transported all the way from the NE Atlantic towards the Arctic. The greatest air temperature deviation was centred east of Svalbard and air temperatures on the West Spitsbergen Shelf were approximately 3-5°C warmer than the 11-year mean.

In February the situation was reverted with Fram Strait being dominated by cold northerly winds and air temperatures are back to normal. But, instead of measuring a decreasing water temperature, the observations showed an increasing water temperature during a period of low air temperature!

This was due to a transport of warm Atlantic Water from the West Spitsbergen Current eastward towards the coastline and into the fjords. In the published paper (Cottier et al., 2007), the warm water flooding is explained by extreme pressure systems influencing Fram Strait and the switch in wind direction over the study area from southerly in January to northerly in February 2006.

The authors expect that wind forcing may also play an important role in the distribution of heat to other Arctic areas.

Finlo Cottier and Frank Nilsen would like to thank The Royal Society for travel grants during the writing process.

Reference
Cottier, F. R., F. Nilsen, M. E. Inall, S. Gerland, V. Tverberg, and H. Svendsen (2007), Wintertime warming of an Arctic shelf in response to large-scale atmospheric circulation, Geophys. Res. Lett., 34, L10607, doi:10.1029/2007GL029948.

GRL Editor’s Highlight:
https://www.agu.org/journals/scripts/highlight.php?pid=2007GL029948

Map illustration of water influx itno Svalbard fjords

Bathymetric map of West Spitsbergen illustrating the spatial extent of the WSC at the shelf break (dark red) and the occurrence of AW on the shelf (pale red) during an upwelling situation with northerly winds (black arrow). Locations of moorings (blue), met. stations (white) and wind stress data point (white τ) are shown. (From Cottier et al. (2007).

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