Sound‐speed structure of the Arctic Ocean and the Greenland Sea Marginal Ice Zone

Abstract Observations were made of oceanic currents, hydrography, and microstructure in the southern Yermak Plateau in summer 2007. The location is in the marginal ice zone at the Arctic Front northwest of Svalbard, where the West Spitsbergen Current (WSC) carries the warm Atlantic Water into the Arctic Ocean. Time series of approximately 1-day duration from five stations (upper 520 m) and of an 8-day duration from a mooring are analyzed to describe the characteristics of internal waves and turbulent mixing. The spectral composition of the internal-wave field over the southern Yermak Plateau is 0.1–0.3 times the midlatitude levels and compares with the most energetic levels in the central Arctic. Dissipation rate and eddy diffusivity below the pycnocline increase from the noise level on the cold side of the front by one order of magnitude on the warm side, where 100-m-thick layers with average diffusivities of 5 × 10−5 m2 s−1 lead to heat loss from the Atlantic Water of 2–4 W m−2. Dissipation in the upper 150 m is well above the noise level at all stations, but strong stratification at the cold side of the front prohibits mixing across the pycnocline. Close to the shelf, at the core of the Svalbard branch of the WSC, diffusivity increases by another factor of 3–6. Here, near-bottom mixing removes 15 W m−2 of heat from the Atlantic layer. Internal-wave activity and mixing show variability related to topography and hydrography; thus, the path of the WSC will affect the cooling and freshening of the Atlantic inflow. When generalized to the Arctic Ocean, diapycnal mixing away from abyssal plains can be significant for the heat budget. Around the Yermak Plateau, it is of sufficient magnitude to influence heat anomaly pulses entering the Arctic Ocean; however, diapycnal mixing alone is unlikely to be significant for regional cooling of the WSC.

Download Full-text

Convection and deep water formation in the Arctic Ocean-Greenland Sea System

Journal of Marine Systems ◽

10.1016/0924-7963(91)90045-v ◽

1991 ◽

Vol 2 (3-4) ◽

pp. 435-450 ◽

Cited By ~ 71

Author(s):

Bert Rudels ◽

Detlef Quadfasel

Keyword(s):

Arctic Ocean ◽

Deep Water ◽

The Arctic ◽

Deep Water Formation ◽

Greenland Sea ◽

The Arctic Ocean ◽

Water Formation

Download Full-text

The East Greenland Current and its impacts on the Nordic Seas: observed trends in the past decade

ICES Journal of Marine Science ◽

10.1093/icesjms/fss079 ◽

2012 ◽

Vol 69 (5) ◽

pp. 841-851 ◽

Cited By ~ 28

Author(s):

Bert Rudels ◽

Meri Korhonen ◽

Gereon Budéus ◽

Agnieszka Beszczynska-Möller ◽

Ursula Schauer ◽

...

Keyword(s):

Arctic Ocean ◽

Deep Water ◽

The Arctic ◽

Greenland Sea ◽

Nordic Seas ◽

East Greenland ◽

The Past ◽

East Greenland Current ◽

Deep Waters ◽

The Arctic Ocean

Abstract Rudels, B., Korhonen, M., Budéus, G., Beszczynska-Möller, A., Schauer, U., Nummelin, A., Quadfasel, D., and Valdimarsson, H. 2012. The East Greenland Current and its impacts on the Nordic Seas: observed trends in the past decade. – ICES Journal of Marine Science, 69: 841–851. For the past 30 years, it has been known that dense waters are created in the Arctic Ocean. However, before the late 1980s, observations indicated that Arctic Ocean deep waters only modified the deep water in the Greenland Sea, which was still thought of as the major source of dense water. In the mid-1990s, this picture began to fade. The deep convection in the Greenland Sea weakened and only Arctic Intermediate Water was formed. A deep salinity maximum was reinforced and a temperature maximum emerged at mid-depth. The densities of the salinity and temperature maxima were those of the deep waters in the Arctic Ocean, and one possibility was that waters below the convection were ventilated by Arctic Ocean deep waters from the East Greenland Current. Between 1998 and 2010, the salinity and temperature of the deep water in the Greenland Sea increased, implying continuous input from the East Greenland Current. Water from the Greenland Sea advected to Fram Strait now has almost Arctic Ocean characteristics and cannot significantly change the outflowing Arctic Ocean waters by mixing in the East Greenland Current, leading to a more-rapid transformation of the deep Greenland Sea water column.

Download Full-text