New Constraints on the Physical and Biological Controls on the Silicon Isotopic Composition of the Arctic Ocean

The silicon isotope composition of silicic acid, δ30Si(OH)4, in the deep Arctic Ocean is anomalously heavy compared to all other deep ocean basins. To further evaluate the mechanisms leading to this condition, δ30Si(OH)4 was examined on US GEOTRACES section GN01 from the Bering Strait to the North Pole. Isotope values in the polar mixed layer showed a strong influence of the transpolar drift. Drift waters contained relatively high [Si(OH)4] with heavy δ30Si(OH)4 consistent with the high silicate of riverine source waters and strong biological Si(OH)4 consumption on the Eurasian shelves. The maximum in silicic acid concentration, [Si(OH)4], within the double halocline of the Canada Basin formed a local minimum in δ30Si(OH)4 that extended across the Canada Basin, reflecting the high-[Si(OH)4] Pacific source waters and benthic inputs of Si(OH)4 in the Chukchi Sea. δ30Si(OH)4 became lighter with the increase in [Si(OH)4] in intermediate and deep waters; however, both Canada Basin deep water and Eurasian Basin deep water were heavier than deep waters from other ocean basins. A preliminary isotope budget incorporating all available Arctic δ30Si(OH)4 data confirms the importance of isotopically heavy inflows in creating the anomalous deep Arctic Si isotope signature, but also reveals a surprising similarity in the isotopic composition of the major inflows compared to outflows across the main gateways connecting the Arctic with the Pacific and the Atlantic. This similarity implies a major role of biological productivity and opal burial in removing light isotopes entering the Arctic Ocean from rivers.

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Age of Canada Basin Deep Waters: A Way to Estimate Primary Production for the Arctic Ocean

Science ◽

10.1126/science.254.5036.1348 ◽

1991 ◽

Vol 254 (5036) ◽

pp. 1348-1350 ◽

Cited By ~ 36

Author(s):

R. W. MACDONALD ◽

E. C. CARMACK

Keyword(s):

Primary Production ◽

Arctic Ocean ◽

Canada Basin ◽

The Arctic ◽

Deep Waters ◽

The Arctic Ocean

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On the 14C and 39Ar Distribution in the Central Arctic Ocean: Implications for Deep Water Formation

Radiocarbon ◽

10.1017/s003382220001451x ◽

1994 ◽

Vol 36 (3) ◽

pp. 327-343 ◽

Cited By ~ 37

Author(s):

Peter Schlosser ◽

Bernd Kromer ◽

Gote Östlund ◽

Brenda Ekwurzel ◽

Gerhard Bönisch ◽

...

Keyword(s):

Arctic Ocean ◽

Deep Water ◽

Atlantic Water ◽

The Arctic ◽

Central Arctic Ocean ◽

Deep Waters ◽

The Arctic Ocean ◽

Bottom Waters ◽

Eurasian Basin ◽

Canadian Basin

We present ΔA14C and 39Ar data collected in the Nansen, Amundsen and Makarov basins during two expeditions to the central Arctic Ocean (RV Polarstern cruises ARK IV/3, 1987 and ARK VIII/3, 1991). The data are used, together with published Δ14C values, to describe the distribution of Δ14C in all major basins of the Arctic Ocean (Nansen, Amundsen, Makarov and Canada Basins), as well as the 39Ar distribution in the Nansen Basin and the deep waters of the Amundsen and Makarov Basins. From the combined Δ14C and 39Ar distributions, we derive information on the mean “isolation ages” of the deep and bottom waters of the Arctic Ocean. The data point toward mean ages of the bottom waters in the Eurasian Basin (Nansen and Amundsen Basins) of ca. 250-300 yr. The deep waters of the Amundsen Basin show slightly higher 3H concentrations than those in the Nansen Basin, indicating the addition of a higher fraction of water that has been at the sea surface during the past few decades. Correction for the bomb 14C added to the deep waters along with bomb 3H yields isolation ages for the bulk of the deep and bottom waters of the Amundsen Basin similar to those estimated for the Nansen Basin. This finding agrees well with the 39Ar data. Deep and bottom waters in the Canadian Basin (Makarov and Canada Basins) are very homogeneous, with an isolation age of ca. 450 yr. Δ14C and 39Ar data and a simple inverse model treating the Canadian Basin Deep Water (CBDW) as one well-mixed reservoir renewed by a mixture of Atlantic Water (29%), Eurasian Basin Deep Water (69%) and brine-enriched shelf water (2%) yield a mean residence time of CBDW of ca. 300 yr.

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Evolution of the Deep Water in the Canadian Basin in the Arctic Ocean

Journal of Physical Oceanography ◽

10.1175/jpo2906.1 ◽

2006 ◽

Vol 36 (5) ◽

pp. 866-874 ◽

Cited By ~ 22

Author(s):

M-L. Timmermans ◽

Chris Garrett

Keyword(s):

Arctic Ocean ◽

Deep Water ◽

Bottom Layer ◽

Canada Basin ◽

The Arctic ◽

Lomonosov Ridge ◽

Geothermal Heat ◽

Makarov Basin ◽

The Arctic Ocean ◽

Canadian Basin

Abstract An overflow of magnitude 0.25 Sv (Sv ≡ 106 m−3 s−1) has been predicted to enter the Makarov Basin (part of the Canadian Basin in the Arctic Ocean) from the Eurasian Basin via a deep gap in the dividing Lomonosov ridge. The authors argue that this overflow does not ventilate the deep Makarov Basin (below 2400 m) where the water is too warm and salty to be compatible with such a large cold fresh inflow. However, complete isolation of the homogeneous bottom layer of the Makarov Basin must be ruled out because changes there are too small to arise from more than a small fraction of the measured geothermal heat flux into the basin. A small cold fresh inflow of about 0.01 Sv from the Amundsen Basin seems to be required. This could occur if the gap in the dividing Lomonosov Ridge is shallower than previously thought. It could also occur if there is active mixing and dilution of the predicted overflow in the gap, leaving only a small fraction to descend into the deep Makarov Basin. Hydraulic theory and hydrographic observations are used to rule out any significant flow of dense water from the Makarov Basin into the deep Canada Basin, confirming previous hypotheses of isolation of the deep water in the Canada Basin.

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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.

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Role of colloidal material in the removal of 234Th in the Canada basin of the Arctic Ocean

Deep Sea Research Part I Oceanographic Research Papers ◽

10.1016/s0967-0637(03)00140-7 ◽

2003 ◽

Vol 50 (10-11) ◽

pp. 1353-1373 ◽

Cited By ~ 44

Author(s):

M. Baskaran ◽

P.W. Swarzenski ◽

D. Porcelli

Keyword(s):

Arctic Ocean ◽

Canada Basin ◽

The Arctic ◽

Colloidal Material ◽

The Arctic Ocean

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Dynamics in the Deep Canada Basin, Arctic Ocean, Inferred by Thermistor Chain Time Series

Journal of Physical Oceanography ◽

10.1175/jpo3032.1 ◽

2007 ◽

Vol 37 (4) ◽

pp. 1066-1076 ◽

Cited By ~ 12

Author(s):

M-L. Timmermans ◽

H. Melling ◽

L. Rainville

Keyword(s):

Time Series ◽

High Resolution ◽

Internal Wave ◽

Arctic Ocean ◽

Temperature Fluctuations ◽

Canada Basin ◽

The Arctic ◽

The Arctic Ocean ◽

Vertical Displacements ◽

Wave Energy Flux

Abstract A 50-day time series of high-resolution temperature in the deepest layers of the Canada Basin in the Arctic Ocean indicates that the deep Canada Basin is a dynamically active environment, not the quiet, stable basin often assumed. Vertical motions at the near-inertial (tidal) frequency have amplitudes of 10– 20 m. These vertical displacements are surprisingly large considering the downward near-inertial internal wave energy flux typically observed in the Canada Basin. In addition to motion in the internal-wave frequency band, the measurements indicate distinctive subinertial temperature fluctuations, possibly due to intrusions of new water masses.

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