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Falkner, KK, Steele M, Woodgate RA, Swift JH, Aagaard K, Morison J.  2005.  Dissolved oxygen extrema in the Arctic Ocean halocline from the North Pole to the Lincoln Sea. Deep-Sea Research Part I-Oceanographic Research Papers. 52:1138-1154.   10.1016/j.dsr.2005.01.007   AbstractWebsite

Dissolved oxygen (02) profiling by new generation sensors was conducted in the Arctic Ocean via aircraft during May 2003 as part of the North Pole Environmental Observatory (NPEO) and Freshwater Switchyard (SWYD) projects. At stations extending from the North Pole to the shelf off Ellesmere Island, such profiles display what appear to be various 02 maxima (with concentrations 70% of saturation or less) over depths of 70-110 m in the halocline, corresponding to salinity and temperature ranges of 33.3-33.9 and -1.7 to -1.5 degrees C. The features appear to be widely distributed: Similar features based on bottle data were recently reported for a subset of the 1997-1998 SHEBA stations in the southern Canada Basin and in recent Beaufort Sea sensor profiles. Oxygen sensor data from August 2002 Chukchi Borderlands (CBC) and 1994 Arctic Ocean Section (AOS) projects suggest that such features arise from interleaving of shelf-derived, O(2)-depleted waters. This generates apparent oxygen maxima in Arctic Basin profiles that would otherwise trend more smoothly from near-saturation at the surface to lower concentrations at depth. For example, in the Eurasian Basin, relatively low O(2) concentrations are observed at salinities of about 34.2 and 34.7. The less saline variant is identified as part of the lower halocline, a layer originally identified by a Eurasian Basin minimum in "NO," which, in the Canadian Basin, is reinforced by additional inputs. The more saline and thus denser variant appears to arise from transformations of Atlantic source waters over the Barents and/or Kara shelves. Additional low-oxygen waters are generated in the vicinity of the Chukchi Borderlands, from Pacific shelf water outflows that interleave with Eurasian waters that flow over the Lomonosov Ridge into the Makarov Basin and then into the Canada Basin. One such input is associated with the well-known silicate maximum that historically has been associated with a salinity of approximate to 33.1. Above that (32 < S < 33), there is a layer moderately elevated in temperature (summer Bering Sea water) that we show is also O(2)-depleted. We propose that these low O(2) waters influence the NPEO and SWYD profiles to varying extents in a manner reflective of the large-scale circulation. The patterns of halocline circulation we infer from the intrusive features defy a simple boundary-following cyclonic flow. These results demonstrate the value of the improved resolution made feasible with continuous O(2) Profiling. In the drive to better understand variability and change in the Arctic Ocean, deployment of appropriately calibrated CTD-O(2) packages offers the promise of important new insights into circulation and ecosystem function. (c) 2005 Elsevier Ltd. All rights reserved.

Jones, EP, Anderson LG, Swift JH.  1998.  Distribution of Atlantic and Pacific waters in the upper Arctic Ocean: Implications for circulation. Geophysical Research Letters. 25:765-768.   10.1029/98gl00464   AbstractWebsite

The Atlantic and Pacific oceans provide source waters for the Arctic Ocean that can be distinguished by their differing nitrate and phosphate concentration relationships. Using these relationships, we estimate the amount of Atlantic and Pacific waters in the surface layer (top 30 m) of the Arctic Ocean. Atlantic source water is dominant in most of the Eurasian Basin and is present in significant amounts in the Makarov Basin north of the East Siberian Sea. Pacific source water is dominant in most of the Canadian Basin and is present in significant amounts in the Amundsen Basin north of Greenland. We deduce circulation patterns from the distributions of Atlantic and Pacific source waters in the surface layer of the Arctic Ocean and conclude that the flow within the surface layer differs from ice drift along the North American and European boundaries of the Polar Basin.

Anderson, LG, Falck E, Jones EP, Jutterstrom S, Swift JH.  2004.  Enhanced uptake of atmospheric CO2 during freezing of seawater: A field study in Storfjorden, Svalbard. Journal of Geophysical Research-Oceans. 109   10.1029/2003jc002120   AbstractWebsite

The waters of Storfjorden, a fjord in southern Svalbard, were investigated in late April 2002. The temperature was at the freezing point throughout the water column; the salinity in the top 30 m was just above 34.8, then increased nearly linearly to about 35.8 at the bottom. Nutrient and oxygen concentrations showed a minimal trend all through the water column, indicating minimal decay of organic matter. Normalized dissolved inorganic carbon, fCO(2), and CFCs increase with depth below the surface mixed layer, while pH decreases. In waters below 50 m, there was an increase in dissolved inorganic carbon, corrected for decay of organic matter using the phosphate profile, corresponding to about 9 g C m(-2) relative to the surface water concentration. We suggest this excess is a result of enhanced air-sea exchange of CO(2) caused by sea ice formation. This enhancement is suggested to be a result of an efficient exchange through the surface film during the ice crystal formation and the rapid transport of the high salinity brine out of the surface layer.

Jutterstrom, S, Jeansson E, Anderson LG, Bellerby R, Jones EP, Smethie WM, Swift JH.  2008.  Evaluation of anthropogenic carbon in the Nordic Seas using observed relationships of N, P and C versus CFCs. Progress in Oceanography. 78:78-84.   10.1016/j.pocean.2007.06.001   AbstractWebsite

Several methods to compute the anthropogenic component of total dissolved inorganic carbon (C-T(anthro)) the ocean have been reported, all in some way deducing (a) the effect by the natural processes, and (b) the background concentration in the pre-industrial scenario. In this work we present a method of calculating C-T(anthro) using nutrient and CFC data, which takes advantage of the linear relationships found between nitrate (N), phosphate (P) and CFC-11 in the Nordic Seas sub-surface waters. The basis of the method is that older water has lower CFC-11 concentration and also has been exposed to more sinking organic matter that has decayed, resulting in the slopes of P versus CFC-11 and N versus CFC-11 being close to the classic Redfield ratio of 1:16. Combining this with the slope in total alkalinity (A(T)) versus CFC-11 to correct for the dissolution of metal carbonates gives us the possibility to deduce the concentration of anthropogenic C-T in the Nordic Seas. This further allowed us to compute the inventory of anthropogenic C-T below 250 m in the Nordic Seas in spring 2002, to similar to 1.2 Gt C. (C) 2008 Elsevier Ltd. All rights reserved.

Anderson, LG, Jones EP, Swift JH.  2003.  Export production in the central Arctic Ocean evaluated from phosphate deficits. Journal of Geophysical Research-Oceans. 108   10.1029/2001jc001057   AbstractWebsite

[1] Primary productivity in the central Arctic Ocean has recently been reported as being much higher than earlier thought. If a significant fraction of this primary production were exported from the immediate surface region, present estimates of the carbon budget for the Arctic Ocean would have to be reassessed. Using the deficit of phosphate in the central Arctic Ocean, we show that the export production is very low, on an average less than 0.5 gC m(-2) yr(-1). This is at least an order of magnitude lower than the total production as measured or estimated from oxygen data, thus indicating extensive recycling of nutrients in the upper waters of the central Arctic Ocean and very little export production.

Anderson, LG, Jones EP, Koltermann KP, Schlosser P, Swift JH, Wallace DWR.  1989.  The first oceanographic section across the Nansen Basin in the Arctic Ocean. Deep-Sea Research. 36:475-482.   10.1016/0198-0149(89)90048-4   AbstractWebsite

The first quasi-synoptic oceanographic section across a major deep basin of the Arctic Ocean reveals three different regimes: a narrow boundary current system along the northern Barents Shelf slope, a wide interior basin regime and a northern boundary current regime with several distinct cores along the Nansen-Gakkel Ridge at 86 degree N. The southern boundary current cores are marked by high oxygen concentrations, high salinities and low temperatures that indicate sources on the shelf and in Fram Strait. The northern boundary current regime contains water mass signatures that are thought to come from the Amundsen Basin as well as from Fram Strait. The Nansen Basin interior is only slowly ventilated from the boundary currents and shelves, the deep water having an age of several decades.

Schlosser, P, Kromer B, Ekwurzel B, Bonisch G, McNichol A, Schneider R, vonReden K, Ostlund HG, Swift JH.  1997.  The first trans-Arctic 14C section: comparison of the mean ages of the deep waters in the Eurasian and Canadian basins of the Arctic Ocean. Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms. 123:431-437.   10.1016/s0168-583x(96)00677-5   AbstractWebsite

We present Delta(14)C data collected during three cruises to the Arctic Ocean that took place in the summers of 1987 (POLARSTERN cruise ARK IV/3), 1991 (ARCTIC 91 Expedition), and 1994 (Arctic Ocean Section 94). The cruise tracks of these three expeditions cover all major basins of the Arctic Ocean (Nansen, Amundsen, Makarov and Canada basins), and can be combined to a trans-Arctic section reaching from the Barents Sea slope to the southern Canada Basin just north of Bering Strait. The section is based on 17 stations covering the entire water column (about 250 data points). The combined Delta(14)C data set was produced from a mixture of large volume samples measured by low-level counting and small volume samples measured by Accelerator Mass Spectrometry (AMS). We use the Delta(14)C section, together with previously published Delta(14)C data from single stations located in several basins of the Arctic Ocean, to derive mean ''ages'': (isolation times) of the deep waters in the Arctic Ocean. We estimate these mean ''ages'' to be approximate to 250 years in the bottom waters of the Eurasian Basin and approximate to 450 years in the Canadian Basin Deep Water. A remarkable feature of the Delta(14)C section is the homogeneity in the C-14 distribution observed in the deep Canadian Basin. Within the measurement precision of about +/- 2 parts per thousand (LV) to about +/- 5 parts per thousand (AMS), we cannot detect significant horizontal or vertical Delta(14)C gradients below 2000 m depth between the northern boundary of the Makarov Basin and the southern margin of the Canada Basin. There is no statistically significant difference between samples measured by AMS and by low-level counting.

Clarke, RA, Swift JH, Reid JL, Koltermann KP.  1990.  The formation of Greenland Sea Deep Water: double diffusion or deep convection? Deep-Sea Research Part a-Oceanographic Research Papers. 37:1385-1424.   10.1016/0198-0149(90)90135-i   AbstractWebsite

An examination of the extensive hydrographic data sets collected by C.S.S. Hudson and F.S. Meteor in the Norwegian and Greenland Seas during February–June 1982 reveals property distributions and circulation patterns broadly similar to those seen in earlier data sets. These data sets, however, reveal the even stronger role played by topography, with evidence of separate circulation patterns and separate water masses in each of the deep basins. The high precision temperature, salinity and oxygen data obtained reveals significant differences in the deep and bottom waters found in the various basins of the Norwegian and Greenland Seas.A comparison of the 1982 data set with earlier sets shows that the renewal of Greenland Sea Deep Water must have taken place sometime over the last decade; however there is no evidence that deep convective renewal of any of the deep and bottom waters in this region was taking place at the time of the observations.The large-scale density fields, however, do suggest that deep convection to the bottom is most likely to occure in the Greenland Basin due to its deep cyclonic circulation. The hypothesis that Greenland Sea Deep Water (GSDW) is formed through dipycnal mixing processes acting on the warm salty core of Atlantic Water entering the Greenland Sea is examined. θ-S correlations and oxygen concentrations suggest that the salinity maxima in the Greenland Sea are the product of at least two separate mixing processes, not the hypothesized single mixing process leading to GSDW.A simple one-dimensional mixed layer model with ice growth and decay demonstrates that convective renewal of GSDW would have occurred within the Greenland Sea had the winter been a little more severe. The new GSDW produced would have only 0.003 less salt and less than 0.04 ml 1−1 greater oxygen concentration than that already in the basin. Consequently, detection of whether new deep water has been produced following a winter cooling season could be difficult even with the best of modern accuracy.

Mawji, E, Schlitzer R, Dodas EM, Abadie C, Abouchami W, Anderson RF, Baars O, Bakker K, Baskaran M, Bates NR et al..  2015.  The GEOTRACES Intermediate Data Product 2014. Marine Chemistry. 177:1-8.   10.1016/j.marchem.2015.04.005   AbstractWebsite

The GEOTRACES Intermediate Data Product 2014 (IDP2014) is the first publicly available data product of the international GEOTRACES programme, and contains data measured and quality controlled before the end of 2013. It consists of two parts: (1) a compilation of digital data for more than 200 trace elements and isotopes (TEls) as well as classical hydrographic parameters, and (2) the eGEOTRACES Electronic Atlas providing a strongly inter-linked on-line atlas including more than 300 section plots and 90 animated 3D scenes. The IDP2014 covers the Atlantic, Arctic, and Indian oceans, exhibiting highest data density in the Atlantic. The TEI data in the IDP2014 are quality controlled by careful assessment of intercalibration results and multi-laboratory data comparisons at cross-over stations. The digital data are provided in several formats, including ASCII spreadsheet, Excel spreadsheet, netCDF, and Ocean Data View collection. In addition to the actual data values the IDP2014 also contains data quality flags and 1-sigma data error values where available. Quality flags and error values are useful for data filtering. Metadata about data originators, analytical methods and original publications related to the data are linked to the data in an easily accessible way. The eGEOTRACES Electronic Atlas is the visual representation of the IDP2014 data providing section plots and a new kind of animated 3D scenes. The basin-wide 3D scenes allow for viewing of data from many cruises at the same time, thereby providing quick overviews of large-scale tracer distributions. In addition, the 3D scenes provide geographical and bathymetric context that is crucial for the interpretation and assessment of observed tracer plumes, as well as for making inferences about controlling processes. (C) 2015 The Authors. Published by Elsevier B.V.

Schlitzer, R, Anderson RF, Dodas EM, Lohan M, Geibere W, Tagliabue A, Bowie A, Jeandel C, Maldonado MT, Landing WM et al..  2018.  The GEOTRACES Intermediate Data Product 2017. Chemical Geology. 493:210-223.   10.1016/j.chemgeo.2018.05.040   AbstractWebsite

The GEOTRACES Intermediate Data Product 2017 (IDP2017) is the second publicly available data product of the international GEOTRACES programme, and contains data measured and quality controlled before the end of 2016. The IDP2017 includes data from the Atlantic, Pacific, Arctic, Southern and Indian oceans, with about twice the data volume of the previous IDP2014. For the first time, the IDP2017 contains data for a large suite of biogeochemical parameters as well as aerosol and rain data characterising atmospheric trace element and isotope (TEI) sources. The TEI data in the IDP2017 are quality controlled by careful assessment of intercalibration results and multi-laboratory data comparisons at crossover stations. The IDP2017 consists of two parts: (1) a compilation of digital data for more than 450 TEIs as well as standard hydrographic parameters, and (2) the eGEOTRACES Electronic Atlas providing an on-line atlas that includes more than 590 section plots and 130 animated 3D scenes. The digital data are provided in several formats, including ASCII, Excel spreadsheet, netCDF, and Ocean Data View collection. Users can download the full data packages or make their own custom selections with a new on-line data extraction service. In addition to the actual data values, the IDP2017 also contains data quality flags and 1-s data error values where available. Quality flags and error values are useful for data filtering and for statistical analysis. Metadata about data originators, analytical methods and original publications related to the data are linked in an easily accessible way. The eGEOTRACES Electronic Atlas is the visual representation of the IDP2017 as section plots and rotating 3D scenes. The basin-wide 3D scenes combine data from many cruises and provide quick overviews of large-scale tracer distributions. These 3D scenes provide geographical and bathymetric context that is crucial for the interpretation and assessment of tracer plumes near ocean margins or along ridges. The IDP2017 is the result of a truly international effort involving 326 researchers from 25 countries. This publication provides the critical reference for unpublished data, as well as for studies that make use of a large cross-section of data from the IDP2017. This article is part of a special issue entitled: Conway GEOTRACES-edited by Tim M. Conway, Tristan Horner, Yves Plancherel, and Aridane G. Gonzalez.

The GSP Group.  1990.  Greenland Sea Project: A venture toward improved understanding of the oceans' role in climate. Eos, Transactions American Geophysical Union. 71:750-751,754-755.   10.1029/90EO00208   Abstract

The Greenland Sea is one of the few major areas where convective renewal of intermediate and deep waters contributes to world ocean ventilation. Basin-scale cyclonic circulation, boundary currents advecting waters of Atlantic and Polar origin, mixing across the fronts related to the boundary currents, wintertime heat loss to the atmosphere, ice formation and related brine release and sequences of penetrative plumes control the renewal. The scales involved range from gyrescale to small-scale and from interannual to hours. This wide range of environmental conditions provides an extreme ecosystem for which biota have evolved specific surviving strategies. In a joint effort, research groups from 11 nations are investigating both the processes and the rates of water-mass transformation and transport and are working on the food chain dynamics and the life cycles of dominant species up to the zooplankton level in a several-year program—the Greenland Sea Project (GSP).

Codispoti, LA, Flagg C, Kelly V, Swift JH.  2005.  Hydrographic conditions during the 2002 SBI process experiments. Deep-Sea Research Part Ii-Topical Studies in Oceanography. 52:3199-3226.   10.1016/j.dsr2.2005.10.007   AbstractWebsite

A review of the hydrographic data from the 2002 Western Arctic Shelf-Basin Interactions (SBI) Process Cruises permits the following conclusions. (1) Temperature-salinity relationships were similar to canonical descriptions, but at five stations in the outer shelf/slope region, warm/high-salinity Atlantic Layer Water appeared to have risen, displaced the lower halocline, and mixed with shelf/upper halocline water. (2) Primary production in the SBI study region was strongly influenced by the advection of dissolved inorganic nitrogen (DIN) entering via Bering Strait. This import of DIN (ammonium + nitrate + nitrite) is modified by local processes, but without the Bering Strait inflow, biological productivity in the SBI region would be much lower. (3) In comparison to the inflowing Atlantic waters, DIN+ urea/phosphate and DIN + urea/silicate ratios in the Pacific waters that dominated the upper similar to 150 m of the water column were low. They were also low relative to Redfield uptake ratios for phytoplankton. (4) Microbial processes continue to destroy DIN in significant quantities as the Pacific waters transit the SBI region. (5) Nitrate and ammonium were the principal contributors to DIN. Nitrite concentrations were always < 0.4 mu M. With a few exceptions urea concentrations were < 0.5 mu M. (6) Moderate concentrations of DIN occurred in surface layers over the shelf in spring, but surface concentrations in the adjacent basin were low, suggesting that basin productivity is low. (7) In summer, DIN depletion in the surface layers was widespread, but a nutricline below similar to 15m contained chlorophyll and dissolved oxygen maxima. production in this layer. (8) A comparison of nutrient and dissolved oxygen concentrations in Suggesting net primary abyssal waters of the Canada Basin with conditions in Fram Strait suggests that the deep metabolism in the SBI region is exceedingly low compared to typical deep-ocean values. (9) The low abyssal metabolism and phosphate-silicate relationships suggest that the maxima in biogenic solutes (ammonium, silicate, etc.) that appear to originate on the shelf and penetrate the interior at halocline depths are not accompanied by comparable concentrations of labile organic matter. Thus. the moderate to high primary production over the shelf and slope supported by the import of DIN from Bering Strait is largelv regenerated over the shelf. (10) Our easternmost section (east of Pt. Barrow) displayed nutrient maxima at depths of similar to 100m as did our three sections to the west, but in this section these signals were not connected to the shelf, and were most likely advected by an eastward shelf-break jet. (c) 2005 Elsevier Ltd. All rights reserved.

Codispoti, LA, Flagg CN, Swift JH.  2009.  Hydrographic conditions during the 2004 SBI process experiments. Deep-Sea Research Part Ii-Topical Studies in Oceanography. 56:1144-1163.   10.1016/j.dsr2.2008.10.013   AbstractWebsite

Western Arctic Shelf-Basin Interactions (SBI) process experiment cruises were conducted during spring and summer in 2002 and 2004. A comparison of the 2004 data with the results from 2002 reveals several similarities but also some distinct differences. Similarities included the following: (1) Dissolved inorganic nitrogen (DIN) (ammonium+nitrate+nitrite) limited phytoplankton growth in both years, suggesting that the fixed-N transport through Bering Strait is a major control on biological productivity. (2) The head of Barrow Canyon was a region of enhanced biological production. (3) Plume-like nutrient maxima and N** minima (a signal of sedimentary denitrification) extending from the shelf into the interior were common except at our easternmost section where the nearshore end of these features intersected the slope. (4) Particularly during summer, oxygen supersaturations were common in or just above the shallow nitracline. (5) Surface waters at our deepest stations were already depleted in nitrate, ammonium and urea during our springtime observations. A major difference between the 2 years was the greater influence of warm, relatively low-nutrient Alaska Coastal Water (ACW) during 2004 entering the region via Bering Strait. This increased inflow of ACW may have reduced photic zone nutrient concentrations. The differences in water temperature and nutrients were most pronounced in the upper similar to 100 db, and the increased influence of warm water in 2004 relative to 2002 was most evident in our East Barrow (EB) section. Although the EB data were collected on essentially the same year-days (29 July-4 August 2002 vs. 29 July-6 August 2004), the surface layers were up to 5 degrees warmer in 2004. While the stronger inflow of ACW in 2004 may have reduced the autochthonous nutrient supply, rates of primary production, bacterial production, and particulate organic carbon export were higher in 2004. This conundrum might be explained by differences in the availability of light. Although, springtime ice thicknesses were greater in 2004 than in 2002, snow cover was significantly less and may have more than compensated for the modest differences in ice thickness vis a vis light penetration. In addition, there was a rapid and extensive retreat of the ice cover in summer 2004. Increased light penetration in 2004 may have allowed phytoplankton to increase utilization of nutrients in the shallow nitracline. In addition, more light combined with warmer temperatures could enhance that fraction of primary production supported by nutrient recycling. Enhanced subsurface primary production during summer 2004 is suggested not only by the results of incubation experiments but by more extreme dissolved oxygen supersaturations in the vicinity of the nitracline. We cannot, however, ignore aliasing that might arise from somewhat different station distributions and timing. It is also possible that the rapid ice retreat and warmer temperatures lead to an acceleration in the seasonal progression of biological processes such that the summer 2004 SBI Process Cruise (HLY 04-03) experiment was observing a state that might have existed a few weeks after completion of the 2002 summer cruise (HLY 02-03). Despite these complications, there is little doubt that biological conditions at the ensemble of hydrographic stations occupied in 2004 during the SBI Process Cruises differed significantly from those at the stations occupied in 2002. (c) 2008 Published by Elsevier Ltd.

Mills, MM, Brown ZW, Lowry KE, van Dijken GL, Becker S, Pal S, Benitez-Nelson CR, Downer MM, Strong AL, Swift JH, Pickart RS, Arrigo KR.  2015.  Impacts of low phytoplankton NO3- :PO43- utilization ratios over the Chukchi Shelf, Arctic Ocean. Deep-Sea Research Part Ii-Topical Studies in Oceanography. 118:105-121.   10.1016/j.dsr2.2015.02.007   AbstractWebsite

The impact of Arctic denitrification is seen in the extremely low values for the geochemical tracer of microbial nitrogen (N) cycle source/sink processes N**. (Mordy at al. 2010). The utility of N** as an oceanic tracer of microbial N cycle processes, however, relies on the assumption that phytoplankton utilize dissolved N and P in Redfield proportions, and thus changes in N** are due to either N-2-fixation or denitrification. We present results from two cruises to the Chukchi Sea that quantify nutrient drawdown, nutrient deficits, and particulate nutrient concentrations to estimate production over the Chukchi Shelf and document lower than Redfield N:P utilization ratios by phytoplankton. These low ratios are used to calculate N** (assuming a Redfield NO3- :Pa-4(3-) utilization ratio) and N**(NR) (using the measured particulate N:P ratios) and, combined with current flow speed and direction measurements, to diagnose denitrification rates on the Chukchi Shelf. Our estimates of denitrification rates are up to 40% higher when Redfield proportions are used. However, the denitrification rates we calculate using N**(NR) are still higher than previous estimates (up to 8 fold) of denitrification on the Chukchi shelf. These estimates suggest that Arctic shelves may be a greater sink of oceanic N than previously thought. (C) 2015 Elsevier Ltd. All rights reserved.

Fransson, A, Chierici M, Anderson LC, Bussmann I, Kattner G, Jones EP, Swift JH.  2001.  The importance of shelf processes for the modification of chemical constituents in the waters of the Eurasian Arctic Ocean: implication for carbon fluxes. Continental Shelf Research. 21:225-242.   10.1016/s0278-4343(00)00088-1   AbstractWebsite

Carbon transformation along the Eurasian shelves in water of Atlantic origin is estimated. Nutrient, oxygen, and inorganic and organic carbon data were used in the evaluation. By comparing the relative deficit of the different chemical constituents it is possible to evaluate the transformation of carbon. It can be seen that the chemical signature in the shelf seas was modified extensively, corresponding to an export production from the upper 50 m in the Barents Sea of 28-32 g C m(-2), which is five times higher than that in the Kara-Laptev Seas and over the deep Eurasian basin. The difference in the export production, computed from the nutrient deficit, and the observed deficit of dissolved inorganic carbon is attributed air-sea exchange of CO2. With this approach the relative oceanic uptake of CO2 from the atmosphere was estimated to be 70% (44 g C m(-2)) in the Barents Sea and 15% (1 g C m(-2)) in the Kara-Laptev Seas, relative to the export production. Of the export production in the Barents Sea, about a quarter is found as DOC. The difference between the chemical signature at the Laptev Sea shelf slope and over the Lomonosov Ridge is negligible, which shows that the transformation of carbon is very small in the surface layers of the Eurasian basin. Combining the chemical transformation with reported volume transports gives an annual export production of 9.6 x 10(12) g C yr(-1) in the Barents Sea. The oceanic uptake of CO2 for the same area is 9.2 x 10(12) g C yr(-1). (C) 2001 Elsevier Science Ltd. All rights reserved.

McLaughlin, FA, Carmack EC, Macdonald RW, Melling H, Swift JH, Wheeler PA, Sherr BF, Sherr EB.  2004.  The joint roles of Pacific and Atlantic-origin waters in the Canada Basin, 1997-1998. Deep-Sea Research Part I-Oceanographic Research Papers. 51:107-128.   10.1016/j.dsr.2003.09.010   AbstractWebsite

Physical and geochemical data collected weekly during the year-long 2800 km drift of the CCGS des Groseilliers show that Canada Basin waters, and in particular the composition of the halocline, can no longer be viewed as laterally homogeneous and in steady state. The halocline was thinner over the Mendeleyev Abyssal Plain and northern Chukchi Plateau. Here, Pacific-origin upper and middle halocline waters occupied the upper 80m of the water column and underlying Atlantic-origin lower halocline waters were fresher, colder and much more ventilated than observed in the past. These new observations of a sub-surface oxygen maximum suggest that outflow from the East Siberian Sea now supplies the Canada Basin lower halocline. East of the Northwind Ridge the halocline was thicker and appeared relatively unchanged. Here Pacific-origin upper and middle halocline waters occupied the top 225 m and Atlantic-origin lower halocline waters were identified by an oxygen minimum. The intensity of the Pacific-origin signal, characterized by a nutrient maximum, was strongest over the Chukchi Gap-the passage between the Chukchi Shelf and Plateau-and the Northwind Abyssal Plain and identified two winter-water spreading pathways. Atlantic-origin waters as much as 0.5degreesC warmer than the historical record were observed over the Chukchi Gap and also over the northern flank of the Chukchi Plateau. These observations signaled that warm-anomaly Fram Strait Branch (FSB) waters, first observed upstream in the Nansen Basin in 1990, had arrived downstream in the Canada Basin eight years later and also indicate two routes whereby FSB waters enter the southern Canada Basin. Although samples were collected throughout one annual cycle, seasonal effects were small and confined to the upper 50 m of the water column. These data show Canada Basin waters are in transition, responding to the effects of upstream change in atmospheric and oceanic circulation. Crown Copyright (C) 2003 Published by Elsevier Ltd. All rights reserved.

Aagaard, K, Andersen R, Swift J, Johnson J.  2008.  A large eddy in the central Arctic Ocean. Geophysical Research Letters. 35   10.1029/2008gl033461   AbstractWebsite

[1] Long-term moored measurements of temperature, salinity, and velocity over the abyssal plain near the North Pole show a rich array of eddy-like structures over a wide range of depths. Here we demonstrate an anticyclone that extends from the surface to at least 1700 m, is about 60 km across, and has a likely origin along the Eurasian continental margin.

Dickson, R, Lazier J, Meincke J, Rhines P, Swift J.  1996.  Long-term coordinated changes in the convective activity of the North Atlantic. Progress in Oceanography. 38:241-295.   10.1016/s0079-6611(97)00002-5   AbstractWebsite

The North Atlantic is a peculiarly convective ocean. The convective renewal of intermediate and deep waters in the Labrador Sea and Greenland/Iceland Sea both contribute significantly to the production and export of North Atlantic Deep Water, thus helping to drive the global thermohaline circulation, while the formation and spreading of 18-Degree Water at shallow-to-intermediate depths off the US eastern seaboard is a major element in the circulation and hydrographic character of the west Atlantic. For as long as time-series of adequate precision have been available to us, it has been apparent that the intensity of convection at each of these sites, and the hydrographic character of their products have been subject to major interannual change, as shown by AAGAARD (1968), CLARKE, SWIFT, REID and KOLTERMANN (1990), and MEINCKE, JONSSON and SWIFT (1992) for the Greenland Sea, in the OWS BRAVO record from the Labrador Sea, (egLAZIER, 1980 et seq.), and at the Panulirus / Hydrostation "S" site in the Northern Sargasso off Bermuda (eg JENKINS, 1982, TALLEY and RAYMER, 1982). This paper reviews the recent history of these changes showing that the major convective centres of the Greenland and Labrador Seas are currently at opposite convective extrema in our postwar record, with vertical exchange at the former site limited to 1000 m or so, but with Labrador Sea convection reaching deeper than previously observed, to over 2300 m. As a result, the deep water of the Greenland Sea has become progressively warmer and more saline since the early '70s as a result of increased horizontal exchange with the Arctic Ocean through Fram Strait, while the Labrador Sea Water has become progressively colder and fresher over the same period through increased vertical exchange; most recently, convection has become deep enough there to reach into the more saline NADW which underlies it, so that cooler, but now saltier and denser LSW has resulted. The horizontal spreading of these changing watermasses in the northern gyre is described from the hydrographic record. The theory is advanced that the scales of atmospheric forcing have imposed a degree of synchrony on convective behaviour at all three sites over the present century, with ventilation at the Sargasso and Greenland Sea sites undergoing a parallel multi-decadal evolution to reach a long term maximum in the 1960s, driven by the twin cells of the North Atlantic Oscillation (NAO). During the NAO minimum of the 1960s, with an extreme Greenland ridge feeding record amounts of fresh water into the northern gyre in the form of the Great Salinity Anomaly, and its partner cell over the Southeast USA causing a southwestward retraction of storm activity (DICKSON and NAMIAS, 1976), the surface freshening and postwar minimum in storm activity in the intervening area of the Labrador Sea also brought a progressive reduction, and ultimately a cessation, of wintertime convection there during the 1960s. In other words, the evolution of winter convective activity during the century was in phase but of different sign at the three sites. In these events, we see strong evidence of a direct impact of the shifting atmospheric circulation on the ocean; while this certainly does not rule out either feedbacks from anomalous ice and SST conditions on the atmosphere, or autonomous oscillations of the ocean's overturning circulation, it does tend to minimise them. Crown copyright (C) 1997 Published by Elsevier Science Ltd

Swift, JH, Aagaard K, Timokhov L, Nikiforov EG.  2005.  Long-term variability of Arctic Ocean waters: Evidence from a reanalysis of the EWG data set. Journal of Geophysical Research-Oceans. 110   10.1029/2004jc002312   AbstractWebsite

We have examined interannual to decadal variability of water properties in the Arctic Ocean using an enhanced version of the 1948-1993 data released earlier under the Gore-Chernomyrdin environmental bilateral agreement. That earlier data set utilized gridded fields with decadal time resolution, whereas we have developed a data set with annual resolution. We find that beginning about 1976, most of the upper Arctic Ocean became significantly saltier, possibly related to thinning of the arctic ice cover. There are also indications that a more local upper ocean salinity increase in the Eurasian Basin about 1989 may not have originated on the shelf, as had been suggested earlier. In addition to the now well-established warming of the Atlantic layer during the early 1990s, there was a similar cyclonically propagating warm event during the 1950s. More remarkable, however, was a pervasive Atlantic layer warming throughout most of the Arctic Ocean from 1964-1969, possibly related to reduced vertical heat loss associated with increased upper ocean stratification. A cold period prevailed during most of the 1970s and 1980s, with several very cold events appearing to originate near the Kara and Laptev shelves. Finally, we find that the silicate maximum in the central Arctic Ocean halocline eroded abruptly in the mid-1980s, demonstrating that the redistribution of Pacific waters and the warming of the Atlantic layer reported from other observations during the 1990s were distinct events separated in time by perhaps 5 years. We have made the entire data set publicly available.

Arrigo, KR, Perovich DK, Pickart RS, Brown ZW, van Dijken GL, Lowry KE, Mills MM, Palmer MA, Balch WM, Bahr F, Bates NR, Benitez-Nelson C, Bowler B, Brownlee E, Ehn JK, Frey KE, Garley R, Laney SR, Lubelczyk L, Mathis J, Matsuoka A, Mitchell GB, Moore GWK, Ortega-Retuerta E, Pal S, Polashenski CM, Reynolds RA, Schieber B, Sosik HM, Stephens M, Swift JH.  2012.  Massive Phytoplankton Blooms Under Arctic Sea Ice. Science. 336:1408.   10.1126/science.1215065   AbstractWebsite

Phytoplankton blooms over Arctic Ocean continental shelves are thought to be restricted to waters free of sea ice. Here, we document a massive phytoplankton bloom beneath fully consolidated pack ice far from the ice edge in the Chukchi Sea, where light transmission has increased in recent decades because of thinning ice cover and proliferation of melt ponds. The bloom was characterized by high diatom biomass and rates of growth and primary production. Evidence suggests that under-ice phytoplankton blooms may be more widespread over nutrient-rich Arctic continental shelves and that satellite-based estimates of annual primary production in these waters may be underestimated by up to 10-fold.

Swift, JH.  1999.  The oceanography of the Arctic Ocean. Current. 15:28-32. Abstract
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Swift, JH, Koltermann KP.  1988.  The origin of Norwegian Sea Deep Water. Journal of Geophysical Research-Oceans. 93:3563-3569.   10.1029/JC093iC04p03563   AbstractWebsite

A nearly homogeneous water mass, the Norwegian Sea Deep Water, is found below 2000-m depth in the Norwegian and Lofoten basins of the Norwegian Sea. Recent observations indicate that this water is a mixture of relatively cold and fresh Greenland Sea Deep Water with warmer, saltier Eurasian Basin Deep Water from the Arctic Ocean. We have found this mixture along the western and southern periphery of the Greenland Sea, near the level where the pressure-compensated densities of the parent water masses are equal. The along-isopycnal mixing produces a remarkably uniform water mass, which can be traced only a short distance away from its entry into the Norwegian Sea through gaps in the mid-ocean ridge north of Jan Mayen Island. Direct measurements of flow through these gaps confirm motion in the proper sense to accomplish this connection.

Zheng, Y, Schlosser P, Swift JH, Jones EP.  1997.  Oxygen utilization rates in the Nansen Basin, Arctic Ocean: implications for new production. Deep-Sea Research Part I-Oceanographic Research Papers. 44:1923-1943.   10.1016/s0967-0637(97)00046-0   AbstractWebsite

In situ consumption of oxygen is balanced by ventilation if the observed distribution of dissolved oxygen below the euphotic zone is in steady state. Apparent oxygen utilization rates (AOURs) can be estimated from the observed oxygen distribution if the waters of the upper layers can be dated. It has been shown previously that tritium/(3)He ages can be used, together with observed oxygen concentrations, to estimate AOURs for waters with ages of several months to several decades. This method is applied to data obtained from the Nansen Basin, Arctic Ocean, during the 1987 cruise of F.S. Polarstern. New production is estimated by depth integration of AOURs calculated for several isopycnals to be 19+/-5g C m(-2) year(-1) for the southern part and 3+/-2 g C m(-2) year(-1) for the northern part of the Nansen Basin section. The results are discussed and compared with previous estimates based on different methods. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.

Jones, EP, Anderson LG, Jutterstrom S, Mintrop L, Swift JH.  2008.  Pacific freshwater, river water and sea ice meltwater across Arctic Ocean basins: Results from the 2005 Beringia Expedition. Journal of Geophysical Research-Oceans. 113   10.1029/2007jc004124   AbstractWebsite

Pacific water, sea ice meltwater, and river water are the primary sources of freshwater in the Arctic Ocean. We have determined their relative fractions on a transect across the Arctic Ocean Section 2005 Expedition onboard IB Oden, which took place from 21 August to 23 September 2005. The transect began north of Alaska, continued through the central Canada Basin to the Alpha Ridge and into the Makarov Basin, and ended in Amundsen Basin. Pacific freshwater and river water were the major sources of freshwater throughout the central Canada Basin and into Makarov Basin, with river water fractions sometimes considerably higher than Pacific water in the top similar to 50 m. Pacific freshwater extended to depths of about 200 m. Pacific water found over the Alpha Ridge and in the Amundsen Basin is suggested to have been transported there in the Transpolar Drift. The inventories of Pacific freshwater and river water were roughly constant along the section through most of the Canada and Makarov basins. River water fractions were greater than those of Pacific freshwater in the Amundsen Basin. Sea ice meltwater fractions were negative (reflecting net ice formation) or near zero throughout most of the section. A comparison of freshwater inventories with those at stations occupied during expeditions in 1991, 1994, and 1996 indicated an increase in river water inventories in the Makarov and Amundsen basins on the Eurasian side of the Arctic Ocean.

Woodgate, RA, Aagaard K, Swift JH, Falkner KK, Smethie WM.  2005.  Pacific ventilation of the Arctic Ocean's lower halocline by upwelling and diapycnal mixing over the continental margin. Geophysical Research Letters. 32   10.1029/2005gl023999   AbstractWebsite

Pacific winter waters, a major source of nutrients and buoyancy to the Arctic Ocean, are thought to ventilate the Arctic's lower halocline either by injection (isopycnal or penetrative) of cold saline shelf waters, or by cooling and freshening Atlantic waters upwelled onto the shelf. Although ventilation at salinity ( S) > 34 psu has previously been attributed to hypersaline polynya waters, temperature, salinity, nutrient and tracer data suggest instead that much of the western Arctic's lower halocline is in fact influenced by a diapycnal mixing of Pacific winter waters ( with S similar to 33.1 psu) and denser eastern Arctic halocline ( Atlantic) waters, the mixing taking place possibly over the northern Chukchi shelf/slope. Estimates from observational data confirm that sufficient quantities of Atlantic water may be upwelled to mix with the inflowing Pacific waters, with volumes implying the halocline over the Chukchi Borderland region may be renewed on timescales of order a year.