Joint effects of boundary currents and thermohaline intrusions on the warming of Atlantic water in the Canada Basin, 1993–2007

[1] The 1990–1991 influx of Atlantic water, both anomalously warm and in greater volume than in the past, enveloped the Chukchi Borderland in the western Canada Basin by 2002 and spread across the southeastern Canada Basin by 2007. Warmer, younger (more ventilated), and less dense Fram Strait Branch waters have replaced colder, older, and denser waters, increasing the temperature of the Fram Strait Branch core from a 50-year or more mean of ∼0.45°C to ∼0.7°C. Physical and geochemical data collected from 1993 to 2007 show that the two main transport mechanisms are the boundary current and thermohaline intrusions, established by large thermal gradients. The boundary current operates in a cyclonic direction whereas the thermohaline intrusions operate in an anticyclonic direction because of the influence of the Beaufort Gyre. This shows that the Beaufort Gyre's effect on ocean circulation extends into the Fram Strait Branch of the Atlantic layer. The boundary current, a fully pan-Arctic structure, is much slower in the Canada Basin than in basins upstream, with an effective speed of ∼0.5 cm/s. The effective spreading rate of the thermohaline intrusions, relative to the core, is 0.2 cm/s. Thermohaline intrusions show signs of dissipation near the Northwind Ridge in 2007 suggesting that as temperature gradients between inflowing and resident waters decrease, they will disappear from the Canada Basin.

[1]  I. Dmitrenko,et al.  Toward a warmer Arctic Ocean: Spreading of the early 21st century Atlantic Water warm anomaly along the Eurasian Basin margins , 2008 .

[2]  J. Piechura,et al.  Pathways of the Greenland Sea warming , 2007 .

[3]  J. Swift,et al.  Atlantic water circulation over the Mendeleev Ridge and Chukchi Borderland from thermohaline intrusions and water mass properties , 2007 .

[4]  L. Timokhov,et al.  Long-term variability of Arctic Ocean waters: Evidence from a reanalysis of the EWG data set , 2005 .

[5]  E. Carmack,et al.  The hydrography of the southern Canada Basin, 2002 , 2005, Polar Biology.

[6]  I. Polyakov,et al.  Variability of the Intermediate Atlantic Water of the Arctic Ocean over the Last 100 Years , 2004 .

[7]  E. Carmack,et al.  Penetration of the 1990s warm temperature anomaly of Atlantic Water in the Canada Basin , 2004 .

[8]  E. Fahrbach,et al.  Arctic warming through the Fram Strait: Oceanic heat transport from 3 years of measurements , 2004 .

[9]  Frank Kauker,et al.  Arctic warming: Evolution and spreading of the 1990s warm event in the Nordic seas and the Arctic Ocean , 2003 .

[10]  A. Proshutinsky,et al.  The role of the Beaufort Gyre in Arctic climate variability: Seasonal to decadal climate scales , 2002 .

[11]  R. Macdonald,et al.  The Canada Basin, 1989–1995: Upstream events and far‐field effects of the Barents Sea , 2002 .

[12]  V. Ivanov,et al.  Confluence and redistribution of Atlantic water in the Nansen, Amundsen and Makarov basins , 2002 .

[13]  Ursula Schauer,et al.  The Arctic Ocean Boundary Current along the Eurasian slope and the adjacent Lomonosov Ridge: Water mass properties, transports and transformations from moored instruments , 2001 .

[14]  J. Hurrell,et al.  The Arctic Ocean Response to the North Atlantic Oscillation , 2000 .

[15]  G. Bönisch,et al.  Renewal and circulation of intermediate waters in the Canadian Basin observed on the SCICEX 96 cruise , 2000 .

[16]  T. Boyd,et al.  Circulation features in the central Arctic Ocean revealed by nuclear fuel reprocessing tracers from Scientific Ice Expeditions 1995 and 1996 , 1999 .

[17]  D. Quadfasel,et al.  The Arctic Circumpolar Boundary Current , 1999 .

[18]  Marvin L. Johnson,et al.  Two circulation regimes of the wind-driven Arctic Ocean , 1997 .

[19]  U. Schauer,et al.  Impact of eastern Arctic shelf waters on the Nansen Basin intermediate layers , 1997 .

[20]  R. Macdonald,et al.  Physical and geochemical properties across the Atlantic/Pacific water mass front in the southern Canadian Basin , 1996 .

[21]  R. Macdonald,et al.  Evidence for warming of Atlantic water in the Southern Canadian Basin of the Arctic Ocean: Results from the Larsen-93 Expedition , 1995 .

[22]  K. Koltermann,et al.  Water masses and circulation in the Eurasian Basin: Results from the Oden 91 expedition , 1994 .

[23]  D. Quadfasel,et al.  A ship of opportunity section to the North Pole: upper ocean temperature observations , 1993 .

[24]  D. Quadfasel,et al.  Warming in the Arctic , 1991, Nature.

[25]  K. Koltermann,et al.  The first oceanographic section across the Nansen Basin in the Arctic Ocean , 1989 .

[26]  E. Lewis,et al.  Mixing in the West Spitsbergen Current , 1984 .

[27]  D. C. Burrell,et al.  Chemical characteristics of water masses in the Amerasian Basin of the Arctic Ocean , 1970 .

[28]  L. V. Worthington.  Oceanographic results of project Skijump I and Skijump II in the Polar Sea, 1951–1952 , 1953 .

[29]  R. Macdonald,et al.  The joint roles of Pacific and Atlantic-origin waters in the Canada Basin, 1997–1998 , 2004 .

[30]  E. Carmack,et al.  The nested structure of Arctic thermohaline intrusions , 2003 .

[31]  R. Macdonald,et al.  Waters of the Makarov and Canada basins , 1997 .

[32]  R. Macdonald,et al.  Changes in temperature and tracer distributions within the Arctic Ocean: results from the 1994 Arctic Ocean section , 1997 .

[33]  L. K. Coachman,et al.  Atlantic Water Circulation in the Canada Basin , 1974 .

[34]  L. K. Coachman,et al.  The Movement of Atlantic Water in the Arctic Ocean , 1963 .

[35]  F. Nansen,et al.  Scientific results : the Norwegian North Polar Expedition 1893-1896 , 1900 .