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Aagaard, K, Barrie L, Carmack E, Garrity C, Jones EP, Lubin D, Macdonald RW, Swift JH, Tucker W, Wheeler PA, Whritner R.  1996.  U.S., Canadian researchers explore Arctic Ocean. EOS, Transactions American Geophysical Union. 77:209,213.   10.1029/96EO00141   Abstract

During July–September 1994, two Canadian and U.S. ice breakers crossed the Arctic Ocean (Figure 1) to investigate the biological, chemical, and physical systems that define the role of the Arctic in global change. The results are changing our perceptions of the Arctic Ocean as a static environment with low biological productivity to a dynamic and productive system. The experiment was called the Arctic Ocean Section (AOS) and the ships were the Canadian Coast Guard ship Louis S. St.-Laurent and the U.S. Coast Guard cutter Polar Sea.

Aagaard, K, Swift JH, Carmack EC.  1985.  Thermohaline circulation in the Arctic Mediterranean Seas. Journal of Geophysical Research-Oceans. 90:4833-4846.   10.1029/JC090iC03p04833   AbstractWebsite

The renewal of the deep North Atlantic by the various overflows of the Greenland-Scotland ridges is only one manifestation of the convective and mixing processes which occur in the various basins and shelf areas to the north: the Arctic Ocean and the Greenland, Iceland, and Norwegian seas, collectively called the Arctic Mediterranean. The traditional site of deep ventilation for these basins is the Greenland Sea, but a growing body of evidence also points to the Arctic Ocean as a major source of deep water. This deep water is relatively warm and saline, and it appears to be a mixture of dense, brine-enriched shelf water with intermediate strata in the Arctic Ocean. The deep water exits the Arctic Ocean along the Greenland slope to mix with the Greenland Sea deep water. Conversely, very cold low-salinity deep water from the Greenland Sea enters the Arctic Ocean west of Spitsbergen. Within the Arctic Ocean, the Lomonosov Ridge excludes the Greenland Sea deep water from the Canadian Basin, leaving the latter warm, saline, and rich in silica. In general, the entire deep-water sphere of the Arctic Mediterranean is constrained by the Greenland-Scotland ridges to circulate internally. Therefore it is certain of the intermediate waters formed in the Greenland and Iceland seas which ventilate the North Atlantic. These waters have a very short residence time in their formation areas and are therefore able to rapidly transmit surface-induced signals into the deep North Atlantic.

Aagaard, K, Fahrbach E, Meincke J, Swift JH.  1991.  Saline outflow from the Arctic Ocean: Its contribution to the deep waters of the Greenland, Norwegian, and Iceland seas. Journal of Geophysical Research-Oceans. 96:20433-20441.   10.1029/91jc02013   AbstractWebsite

Since 1985 various investigators have proposed that Norwegian Sea deep water (NSDW) is formed by mixing of warm and saline deep water from the Arctic Ocean with the much colder and fresher deep water formed by convection in the Greenland Sea (GSDW). We here report on new observations which suggest significant modification and expansion of this conceptual model. We find that saline outflows from the Arctic Ocean result in several distinct intermediate and deep salinity maxima within the Greenland Sea; the southward transport of the two most saline modes is probably near 2 Sv. Mixing of GSDW and the main outflow core found over the Greenland slope, derived from about 1700 m in the Arctic Ocean, cannot by itself account for the properties of NSDW. Instead, the formation of NSDW must at least in part involve a source which in the Arctic Ocean is found below 2000 m. The mixing of various saline outflows is diapycnal. While significant NSDW production appears to occur in northern Fram Strait, large amounts of saline Arctic Ocean outflow also traverse the western Greenland Sea without mixing and enter the Iceland Sea. During the past decade, deep convection in the Greenland Sea has been greatly reduced, while deep outflow from the Arctic Ocean appears to have continued, resulting in a markedly warmer, slightly more saline, and less dense deep regime in the Greenland Sea.

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.

Anderson, LG, Tanhua T, Bjork G, Hjalmarsson S, Jones EP, Jutterstrom S, Rudels B, Swift JH, Wahlstom I.  2010.  Arctic ocean shelf-basin interaction: An active continental shelf CO2 pump and its impact on the degree of calcium carbonate solubility. Deep-Sea Research Part I-Oceanographic Research Papers. 57:869-879.   10.1016/j.dsr.2010.03.012   AbstractWebsite

The Arctic Ocean has wide shelf areas with extensive biological activity including a high primary productivity and an active microbial loop within the surface sediment. This in combination with brine production during sea ice formation result in the decay products exiting from the shelf into the deep basin typically at a depth of about 150 m and over a wide salinity range centered around S similar to 33. We present data from the Beringia cruise in 2005 along a section in the Canada Basin from the continental margin north of Alaska towards the north and from the International Siberian Shelf Study in 2008 (ISSS-08) to illustrate the impact of these processes. The water rich in decay products, nutrients and dissolved inorganic carbon (DIC), exits the shelf not only from the Chukchi Sea, as has been shown earlier, but also from the East Siberian Sea. The excess of DIC found in the Canada Basin in a depth range of about 50-250 m amounts to 90 +/- 40 g C m(-2). If this excess is integrated over the whole Canadian Basin the excess equals 320 +/- 140 x 10(12) g C. The high DIC concentration layer also has low pH and consequently a low degree of calcium carbonate saturation, with minimum aragonite values of 60% saturation and calcite values just below saturation. The mean age of the waters in the top 300 m was calculated using the transit time distribution method. By applying a future exponential increase of atmospheric CO2 the invasion of anthropogenic carbon into these waters will result in an under-saturated surface water with respect to aragonite by the year 2050, even without any freshening caused by melting sea ice or increased river discharge. (C) 2010 Elsevier Ltd. All rights reserved.

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.

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.

Anderson, LG, Bjork G, Holby O, Jones EP, Kattner G, Koltermann KP, Liljeblad B, Lindegren R, Rudels B, Swift J.  1994.  Water masses and circulation in the Eurasian Basin: Results from the Oden 91 expedition. Journal of Geophysical Research-Oceans. 99:3273-3283.   10.1029/93jc02977   AbstractWebsite

The Oden 91 North Pole expedition obtained oceanographic measurements on four sections in the Nansen and Amundsen basins of the Eurasian Basin and in the Makarov Basin of the Canadian Basin, thereby proving the feasibility of carrying out a typical oceanographic program using an icebreaker in the Arctic Ocean. The data show greater spatial variability in water structure and circulation than was apparent from previous data. The results show that a clear front exists between the Eurasian and Canadian basins such that upper halocline water in the Canadian Basin is almost absent from the Eurasian Basin. The lower halocline water produced in the Barents-Kara Sea region permeates much of the Eurasian Basin and flows along the continental slope into the Canadian Basin. The deeper circulation is strongly influenced by topography. Three return flows of the Atlantic layer are identified, one over the Nansen-Gakkel Ridge, one over the Lomonosov Ridge, and a third flowing from the Canadian Basin. The slight differences observed in salinity and temperature characteristics of the deeper waters of the Nansen and Amundsen basins do not lead to an obvious explanation of their origin or flow pattern.

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.

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.

Arrigo, KR, Perovich DK, Pickart RS, Brown ZW, van Dijken GL, Lowry KE, Mills MM, Palmer MA, Balch WM, Bates NR, Benitez-Nelson CR, Brownlee E, Frey KE, Laney SR, Mathis J, Matsuoka A, Greg Mitchell B, Moore GWK, Reynolds RA, Sosik HM, Swift JH.  2014.  Phytoplankton blooms beneath the sea ice in the Chukchi sea. Deep Sea Research Part II: Topical Studies in Oceanography. 105:1-16.   10.1016/j.dsr2.2014.03.018   AbstractWebsite

In the Arctic Ocean, phytoplankton blooms on continental shelves are often limited by light availability, and are therefore thought to be restricted to waters free of sea ice. During July 2011 in the Chukchi Sea, a large phytoplankton bloom was observed beneath fully consolidated pack ice and extended from the ice edge to >100 km into the pack. The bloom was composed primarily of diatoms, with biomass reaching 1291 mg chlorophyll a m−2 and rates of carbon fixation as high as 3.7 g C m−2 d−1. Although the sea ice where the bloom was observed was near 100% concentration and 0.8–1.2 m thick, 30–40% of its surface was covered by melt ponds that transmitted 4-fold more light than adjacent areas of bare ice, providing sufficient light for phytoplankton to bloom. Phytoplankton growth rates associated with the under-ice bloom averaged 0.9 d−1 and were as high as 1.6 d−1. We argue that a thinning sea ice cover with more numerous melt ponds over the past decade has enhanced light penetration through the sea ice into the upper water column, favoring the development of these blooms. These observations, coupled with additional biogeochemical evidence, suggest that phytoplankton blooms are currently widespread on nutrient-rich Arctic continental shelves and that satellite-based estimates of annual primary production in waters where under-ice blooms develop are ~10-fold too low. These massive phytoplankton blooms represent a marked shift in our understanding of Arctic marine ecosystems.

Bjork, G, Jakobsson M, Rudes B, Swift JH, Anderson L, Darby DA, Backman J, Coakley B, Winsor P, Polyak L, Edwards M.  2007.  Bathymetry and deep-water exchange across the central Lomonosov Ridge at 88-89°N. Deep-Sea Research Part I-Oceanographic Research Papers. 54:1197-1208.   10.1016/j.dsr.2007.05.010   AbstractWebsite

Seafloor mapping of the central Lomonosov Ridge using a multibeam echo-sounder during the Beringia/Healy-Oden Trans-Arctic Expedition (HOTRAX) 2005 shows that a channel across the ridge has a substantially shallower sill depth than the similar to 2500 m indicated in present bathymetric maps. The multibeam survey along the ridge crest shows a maximum sill depth of about 1870 m. A previously hypothesized exchange of deep water from the Amundsen Basin to the Makarov Basin in this area is not confirmed. On the contrary, evidence of a deep-water flow from the Makarov to the Amundsen Basin was observed, indicating the existence of a new pathway for Canadian Basin Deep Water toward the Atlantic Ocean. Sediment data show extensive current activity along the ridge crest and along the rim of a local Intra Basin within the ridge structure.(c) 2007 Elsevier Ltd. All rights reserved.

Brewer, PG, Broecker WS, Jenkins WJ, Rhines PB, Rooth CG, Swift JH, Takahashi T, Williams RT.  1983.  A climatic freshening of the deep Atlantic north of 50°N over the past 20 years. Science. 222:1237-1239.   10.1126/science.222.4629.1237   AbstractWebsite

Observations made in summer 1981 show a significant and widespread decrease in salinity, averaging 0.02 per mil, in deep waters of the subpolar North Atlantic over the past two decades. This implies a relatively rapid response of deep water formation to climatic perturbation.

Brown, ZW, Casciotti KL, Pickart RS, Swift JH, Arrigo KR.  2015.  Aspects of the marine nitrogen cycle of the Chukchi Sea shelf and Canada Basin. Deep-Sea Research Part Ii-Topical Studies in Oceanography. 118:73-87.   10.1016/j.dsr2.2015.02.009   AbstractWebsite

As a highly productive, seasonally ice-covered sea with an expansive shallow continental shelf, the Chukchi Sea fuels high rates of sedimentary denitrification. This contributes to its fixed nitrogen (N) deficit relative to phosphorus (P), which is among the largest in the global ocean, making the Chukchi Sea severely N-limited during the phytoplankton growth season. Here, we examine aspects of the N cycle on the Chukchi Sea shelf and the downstream Canada Basin using nutrients, dissolved oxygen (O-2), and the stable isotopes of nitrate (NO3-). In the northward flow path across the Chukchi shelf, bottom waters experienced strong O-2 drawdown, from which we calculated a nitrification rate of 1.3 mmol m(-2) d(-1). This nitrification was likely primarily in sediments and directly fueled sedimentary denitrification, historically measured at similar rates. We observed significant accumulations of ammonium (NH4+) in bottom waters of the Chukchi shelf (up to > 5 mu M), which were inversely correlated with delta N-15(NO3), indicating a sediment source of N-15-enriched NH4+. This is consistent with a process of coupled partial nitrification-denitrification (CPND), which imparts significant N-15 enrichment and O-18 depletion to Pacific-origin NO3-. This CPND mechanism is consistent with a significant decrease in delta O-18(NO3) relative to Bering Sea source waters, indicating that at least 58% of NO3- populating the Pacific halocline was regenerated during its transit across the North Bering and Chukchi shelves, rather than arriving preformed from the Bering Sea slope. This Pacific-origin NO3- propagates into the Canada Basin and towards the North Atlantic, being significantly N-15-enriched and O-18-depleted relative to the underlying Atlantic waters. (C) 2015 Published by Elsevier Ltd.

Carmack, EC, Aagaard K, Swift JH, Macdonald RW, McLaughlin FA, Jones EP, Perkin RG, Smith JN, Ellis KM, Killius LR.  1997.  Changes in temperature and tracer distributions within the Arctic Ocean: Results from the 1994 Arctic Ocean section. Deep-Sea Research Part Ii-Topical Studies in Oceanography. 44:1487-+.   10.1016/s0967-0645(97)00056-8   AbstractWebsite

Major changes in temperature and tracer properties within the Arctic Ocean are evident in a comparison of data obtained during the 1994 Arctic Ocean Section to earlier measurements. (1) Anomalously warm and well-ventilated waters are now found in the Nansen, Amundsen and Makarov basins, with the largest temperature differences, as much as 1 degrees C, in the core of the Atlantic layer (200-400 m). This thermohaline transition appears to follow from two distinct mechanisms: narrow (order 100 km), topographically-steered cyclonic flows that rapidly carry new water around the perimeters of the basins; and multiple intrusions, 40-60 m thick, which extend laterally into the basin interiors. (2) Altered nutrient distributions that within the halocline distinguish water masses of Pacific and Atlantic origins likewise point to a basin-wide redistribution of properties. (3) Distributions of CFCs associated with inflows from adjacent shelf regions and from the Atlantic demonstrate recent ventilation to depths exceeding 1800 m. (4) Concentrations of the pesticide HCH in the surface and halocline layers are supersaturated with respect to present atmospheric concentrations and show that the ice-capped Arctic Ocean is now a source to the global atmosphere of this contaminant. (5) The radionuclide I-129 is now widespread throughout the Arctic Ocean. Although the current level of I-129 level poses no significant radiological threat, its rapid arrival and wide distribution illustrate the speed and extent to which waterborne contaminants are dispersed within the Arctic Ocean on pathways along which other contaminants can travel from western European or Russian sources. (C) 1998 Elsevier Science Ltd. All rights reserved.

Carmack, EC, Aagaard K, Swift JH, Perkin RG, McLaughlin FA, Macdonald RW, Jones EP.  1998.  Thermohaline transitions. Physical processes in lakes and oceans. ( Imberger J, Ed.).:179-186., Washington, DC: American Geophysical Union Abstract
Carter, BR, Feely RA, Mecking S, Cross JN, Macdonald AM, Siedlecki SA, Talley LD, Sabine CL, Millero FJ, Swift JH, Dickson AG, Rodgers KB.  2017.  Two decades of Pacific anthropogenic carbon storage and ocean acidification along Global Ocean Ship-lebased Hydrographic Investigations Program sections P16 and P02. Global Biogeochemical Cycles. 31:306-327.   10.1002/2016gb005485   AbstractWebsite

A modified version of the extended multiple linear regression (eMLR) method is used to estimate anthropogenic carbon concentration (C-anth) changes along the Pacific P02 and P16 hydrographic sections over the past two decades. P02 is a zonal section crossing the North Pacific at 30 degrees N, and P16 is a meridional section crossing the North and South Pacific at similar to 150 degrees W. The eMLR modifications allow the uncertainties associated with choices of regression parameters to be both resolved and reduced. Canth is found to have increased throughout the water column from the surface to similar to 1000 m depth along both lines in both decades. Mean column Canth inventory increased consistently during the earlier (1990s-2000s) and recent (2000s-2010s) decades along P02, at rates of 0.53 +/- 0.11 and 0.46 +/- 0.11 mol Cm-2 a(-1), respectively. By contrast, Canth storage accelerated from 0.29 +/- 0.10 to 0.45 +/- 0.11 mol Cm-2 a(-1) along P16. Shifts in water mass distributions are ruled out as a potential cause of this increase, which is instead attributed to recent increases in the ventilation of the South Pacific Subtropical Cell. Decadal changes along P16 are extrapolated across the gyre to estimate a Pacific Basin average storage between 60 degrees S and 60 degrees N of 6.1 +/- 1.5 PgC decade(-1) in the earlier decade and 8.8 +/- 2.2 PgC decade(-1) in the recent decade. This storage estimate is large despite the shallow Pacific Canth penetration due to the large volume of the Pacific Ocean. By 2014, Canth storage had changed Pacific surface seawater pH by -0.08 to -0.14 and aragonite saturation state by -0.57 to -0.82.

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.

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.

Cooper, AR, Varshney.Ak, Sarkar SK, Swift J, Yen F, Klein L.  1972.  Some aspects of the thermal history of lunar glass. Journal of the American Ceramic Society. 55:260-264.   10.1111/j.1151-2916.1972.tb11276.x   AbstractWebsite

Electron microprobe examination revealed that glassy lunar fragments had inclusions as well as boundaries between mineral glasses of different compositions. Glassy lunar spherules (40 to 60 μm in diameter) showed detectable heterogeneity less marked than that of the fragments. The room-temperature refractive indices and densities of the spherules are changed by heat-treating them at 500° to 7O0°C. The large increases (as much as 2% in density and 0.7% in index of refraction) are difficult to explain on the basis of classical glass-transition phenomena alone unless extremely rapid cooling rates are assumed. Further, the spherules darkened significantly when they were heated in air or a medium vacuum (∼10−5 mm Hg) above 625°C.

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

Downes, SM, Key RM, Orsi AH, Speer KG, Swift JH.  2012.  Tracing Southwest Pacific Bottom Water Using Potential Vorticity and Helium-3. Journal of Physical Oceanography. 42:2153-2168.   10.1175/jpo-d-12-019.1   AbstractWebsite

This study uses potential vorticity and other tracers to identify the pathways of the densest form of Circumpolar Deep Water in the South Pacific, termed "Southwest Pacific Bottom Water" (SPBW), along the 28.2 kg m(-3) surface. This study focuses on the potential vorticity signals associated with three major dynamical processes occurring in the vicinity of the Pacific-Antarctic Ridge: 1) the strong flow of the Antarctic Circumpolar Current (ACC), 2) lateral eddy stirring, and 3) heat and stratification changes in bottom waters induced by hydrothermal vents. These processes result in southward and downstream advection of low potential vorticity along rising isopycnal surfaces. Using delta He-3 released from the hydrothermal vents, the influence of volcanic activity on the SPBW may be traced across the South Pacific along the path of the ACC to Drake Passage. SPBW also flows within the southern limb of the Ross Gyre, reaching the Antarctic Slope in places and contributes via entrainment to the formation of Antarctic Bottom Water. Finally, it is shown that the magnitude and location of the potential vorticity signals associated with SPBW have endured over at least the last two decades, and that they are unique to the South Pacific sector.

Ekwurzel, B, Schlosser P, Mortlock RA, Fairbanks RG, Swift JH.  2001.  River runoff, sea ice meltwater, and Pacific water distribution and mean residence times in the Arctic Ocean. Journal of Geophysical Research-Oceans. 106:9075-9092.   10.1029/1999jc000024   AbstractWebsite

Hydrographic and tracer data collected during ARK IV/3 (FS Polarstern in 1987), ARCTIC91 (IB Oden), and AOS94 (CCGS Louis S. St-Laurent) expeditions reveal the evolution of the near-surface waters in the Arctic Ocean during the late 1980s and early 1990s. Salinity, nutrients, dissolved oxygen, and delta (18)O data are used to quantify the components of Arctic freshwater: river runoff, sea ice meltwater, and Pacific water. The calculated river runoff fractions suggest that in 1994 a large portion of water from the Pechora, Oh, Yenisey, Kotuy, and Lena Rivers did not flow off the shelf closest to their river deltas, but remained on the shelf and traveled via cyclonic circulation into the Laptev and East Siberian Seas. River runoff flowed off the shelf at the Lomonosov Ridge and most left the shelf at the Mendeleyev Ridge. ARCTIC91 and AOS94 Pacific water fraction estimates of Upper Halocline Water, the traditionally defined core of the Pacific water mass, document a decrease in extent compared to historical data. The front between Atlantic water and Pacific water shifted from the Lomonosov Ridge location in 1991 to the Mendeleyev Ridge in 1994. The relative age structure of the upper waters is described by using the (3)H-(3)He age. The mean (3)H-(3)He age measured in the halocline within the salinity surface of 33.1 +/- 0.3 is 4.3 +/- 1.7 years and that for the 34.2 +/- 0.2 salinity surface is 9.6 +/- 4.6 years. Lateral variations in the relative age structure within the halocline and Atlantic water support the well-known cyclonic boundary current circulation.

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.