Publications

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Book Chapter
Swift, JH.  1986.  The Arctic waters. The Nordic Seas. ( Hurdle BG, Ed.).:129-153., New York: Springer-Verlag Abstract

Thorough, multidisciplinary account of the physical environment of this ocean area which includes the Greenland, Barents and Norwegian seas. Includes chapters on climatology; ice cover; the physical properties of the sea ice cover; brief overview of the physical oceanography; the arctic waters; the sound-speed structure; features of fjord and ocean interaction; tide, bathymetry; seafloor topography, sediments and paleoenvironments; geophysical and geochemical signatures and plate tectonics.

Swift, JH.  1985.  A few comments on a recent deep-water freshening. Glaciers, ice sheets, and sea level : effect of a CO2-induced climatic change. :129-138., Washington, D.C.: U.S. Dep. of Energy Abstract
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Swift, JH.  1995.  A few notes on a recent deep-water freshening. Natural climate variability on decade-to-century time scales. ( Council N, Ed.).:290-294., Washington, D.C.: National Academy Press Abstract
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Swift, JH.  1984.  A recent -S Shift in the deep water of the northern North Atlantic. Climate processes and climate sensitivity. 5( Hansen JE, Takahashi T, Eds.).:39-47., Washington, D.C.: American Geophysical Union Abstract

Papers presented at the Fourth Biennial Maurice Ewing Symposium held at Palisades, NY, October 25-27, 1982 arranged under the headings: Atmosphere and ocean dynamics; Hydrologic cycle and clouds; Albedo and radiation processes; Cryospheric processes; Ice cores and glacial history; Ocean chemistry.

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
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Meincke, J, Jonsson S, Swift JH.  1992.  Variability of convective conditions in the Greenland Sea. Hydrobiological variability in the ICES area, 1980-1989. 195( Dickson RR, Maelkki P, Radach G, Saetre R, Sissenwine MP, Meincke J, Eds.).:32-39., Copenhagen (Denmark): ICES Abstract

Recent observations and data compilations show decadal and interannual variations in the depth of wintertime convection in the Greenland Sea. In a qualitative study the fluctuations are related to changes in wind and thermohaline forcing. Changes in both wind-stress curl and sea-ice cover concur with the results from hydrographic observations indicating that no renewal of deep water has taken place during the 1980s.

Conference Proceedings
Swift, JH.  1984.  Review of North Atlantic source waters. North Atlantic deep water formation : proceedings of a workshop held at Lamont-Doherty Geological Observatory. NASA Publication CP-2367( Bennett T, Broecker WS, Hansen JE, Eds.).:2-4., Palisades, New York: National Aeronautics and Space Administration, Scientific and Technical Information Branch Abstract
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Journal Article
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.

Livingston, HD, Swift JH, Ostlund HG.  1985.  Artificial radionuclide tracer supply to the Denmark Strait overflow between 1972 and 1981. Journal of Geophysical Research-Oceans. 90:6971-6982.   10.1029/JC090iC04p06971   AbstractWebsite

Measurements of the concentrations of the artificial radionuclides 3H, 137Cs, and 90Sr in the northern Irminger Sea in 1972 and 1981 are reported. In both years, tracer measurements from this area included data from samples of the dense overflow water from the north through Denmark Strait. All three tracers were strongly correlated inversely with salinity in the dense outflows—the tracer maxima being related directly to the salinity minimum. When the tracer characteristics in the outflows in 1972 and 1981 were compared, concentrations of all in 1981 were observed to be about double the 1972 values. The individual tracer concentrations—on a decay-corrected, density-normalized basis—were higher in increasing order: 90Sr (+93%) < 3H (+115%) < 137Cs (+150%). The relatively greater increases for 3H and 137Cs were attributed to contributions of new sources of these tracers in northern surface waters: the 3H source is argued to derive from atmospheric hydrological recycling, whereas the 137Cs source is identified as the input to the Greenland and Iceland seas of advected European nuclear fuel reprocessing wastes. Both the tracer and hydrographic data are used to identify northern locations of intermediate water formation capable of supplying the observed dense overflow water characteristics. It is argued, from the time taken for the overflow water to reflect the new surface 137Cs source, that transport from the source to the overflow can be quite rapid (about 2 years).

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.

Woodgate, RA, Aagaard K, Swift JH, Smethie WM, Falkner KK.  2007.  Atlantic water circulation over the Mendeleev Ridge and Chukchi Borderland from thermohaline intrusions and water mass properties. Journal of Geophysical Research-Oceans. 112   10.1029/2005jc003416   AbstractWebsite

[ 1] Hydrographic and tracer data from 2002 illustrate Atlantic water pathways and variability in the Mendeleev Ridge and Chukchi Borderland (CBLMR) region of the Arctic Ocean. Thermohaline double diffusive intrusions (zigzags) dominate both the Fram Strait (FSBW) and Barents Sea Branch Waters (BSBW) in the region. We show that details of the zigzags' temperature-salinity structure partially describe the water masses forming the intrusions. Furthermore, as confirmed by chemical tracers, the zigzags' peaks contain the least altered water, allowing assessment of the temporal history of the Atlantic waters. Whilst the FSBW shows the 1990s warming and then a slight cooling, the BSBW has continuously cooled and freshened over a similar time period. The newest boundary current waters are found west of the Mendeleev Ridge in 2002. Additionally, we show the zigzag structures can fingerprint various water masses, including the boundary current. Using this, tracer data and the advection of the 1990s warming, we conclude the strongly topographically steered boundary current, order 50 km wide and found between the 1500 m and 2500 m isobaths, crosses the Mendeleev Ridge north of 80 degrees N, loops south around the Chukchi Abyssal Plain and north around the Chukchi Rise, with the 1990s warming having reached the northern ( but not the southern) Northwind Ridge by 2002. Pacific waters influence the Atlantic layers near the shelf and over the Chukchi Rise. The Northwind Abyssal Plain is comparatively stagnant, being ventilated only slowly from the north. There is no evidence of significant boundary current flow through the Chukchi Gap.

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.

The Polarstern Shipboard Scientific Party.  1988.  Breakthrough in Arctic deep-sea research; the R/V Polarstern expedition 1987. EOS, Transactions, American Geophysical Union. 69:665,676--678., Washington, DC, United States (USA): American Geophysical Union, Washington, DC   10.1029/EO069i025p00665   AbstractWebsite

During summer 1987, the R/V Polarstern of the Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Federal Republic of Germany (FRG), succeeded in penetrating the eastern Arctic ice pack as far north as the Nansen-Gakkel Ridge in the central eastern Arctic Basin. Our northernmost location, at 86°H′N (Figure 1), was further north than any surface vessel dedicated to marine research has attained previously, although Soviet nuclear-powered ice breakers have managed to penetrate to the North Pole. Prior to this cruise, most knowledge about the eastern Arctic Basin came from remote sensing techniques, Nansen's Fram expedition during 1893–1896 [Bøggild, 1906; Gran, 1904; Nansen, 1902, 1904, 1906], Russian ice camps [Gordienko and Laktionov, 1969], the U.S. ice island camps Fram I-Fram IV, 1979–1982 [Hunkins et al, 1979; Baggeroer and Dyer, 1982; Manley et al, 1982; Kristoffersen, 1982; Kristoffersen et al, 1982; Kristoffersen and Husebye, 1985], and explorations by submarines.

Talley, LD, Feely RA, Sloyan BM, Wanninkhof R, Baringer MO, Bullister JL, Carlson CA, Doney SC, Fine RA, Firing E, Gruber N, Hansell DA, Ishii M, Johnson GC, Katsumata K, Key RM, Kramp M, Langdon C, Macdonald AM, Mathis JT, McDonagh EL, Mecking S, Millero FJ, Mordy CW, Nakano T, Sabine CL, Smethie WM, Swift JH, Tanhua T, Thurnherr AM, Warner MJ, Zhang J-Z.  2016.  Changes in Ocean Heat, Carbon Content, and Ventilation: A Review of the First Decade of GO-SHIP Global Repeat Hydrography. Annual Review of Marine Science. 8:185-215.   10.1146/annurev-marine-052915-100829   AbstractWebsite

Global ship-based programs, with highly accurate, full water column physical and biogeochemical observations repeated decadally since the 1970s, provide a crucial resource for documenting ocean change. The ocean, a central component of Earth's climate system, is taking up most of Earth's excess anthropogenic heat, with about 19% of this excess in the abyssal ocean beneath 2,000 m, dominated by Southern Ocean warming. The ocean also has taken up about 27% of anthropogenic carbon, resulting in acidification of the upper ocean. Increased stratification has resulted in a decline in oxygen and increase in nutrients in the Northern Hemisphere thermocline and an expansion of tropical oxygen minimum zones. Southern Hemisphere thermocline oxygen increased in the 2000s owing to stronger wind forcingand ventilation. The most recent decade of global hydrography has mapped dissolved organic carbon, a large, bioactive reservoir, for the first time and quantified its contribution to export production (∼20%) and deep-ocean oxygen utilization. Ship-based measurements also show that vertical diffusivity increases from a minimum in the thermocline to a maximum within the bottom 1,500 m, shifting our physical paradigm of the ocean's overturning circulation.

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.

Smethie, WM, Chipman DW, Swift JH, Koltermann KP.  1988.  Chlorofluoromethanes in the Arctic mediterranean seas: evidence for formation of bottom water in the Eurasian Basin and deep-water exchange through Fram Strait. Deep-Sea Research Part a-Oceanographic Research Papers. 35:347-369.   10.1016/0198-0149(88)90015-5   AbstractWebsite

During July–August of 1984, the polar research vessel R.V. Polarstern occupied sections of oceanographic stations in and north of Fram Strait and across the Greenland Sea (Boreas Basin) south of Fram Strait. The temperature, salinity and chlorofluoromethane (CFM) data for the Polarstern stations within the Eurasian Basin reveal two deep-water masses, Eurasian Basin Bottom Water (EBBW) which lies below the σ2 = 37.46 density surface and Eurasian Basin Deep Water (EBDW) which lies above this surface. The depth of this surface is close to the 2600 m sill depth of Fram Strait. The CFM, temperature and salinity distributions suggest that EBBW is partially composed of dense, high salinity shelf water advected into the deep Eurasian Basin, where it probably circulates around the basin in a deep cyclonic boundary current. An upper limit of about 0.1 Sv was estimated from the CFM data for the transport of pure high salinity shelf water into the Eurasian Basin below 3000 m. These data together with data collected on previous cruises to the Norwegian and Greenland seas reveal that EBDW exchanges with water masses south of Fram Strait, first flowing through Fram Strait in a narrow (<10 km) deep boundary current, then mixing with Greenland Sea Deep Water in the periphery of the Greenland Gyre to form new Norwegian Sea Deep Water (NSDW). Some of this new NSDW flows southeastward into the Norwegian Sea and a mixture of old and new NSDW flows northward on the eastern side of Fram Strait, returning to the Eurasian Basin. We estimate the volume transport of EBDW southwrd through Fram Strait to be 0.80–0.93 Sv. Volume transports between the deep Greenland and deep Norwegian seas and between the surface and deep Greenland Sea were also estimated with respective values of 0.80–0.93 Sv and 0.50 –0.52 Sv.

Swift, JH.  1984.  The circulation of the Denmark Strait and Iceland-Scotland overflow waters in the North Atlantic. Deep-Sea Research Part a-Oceanographic Research Papers. 31:1339-1355.   10.1016/0198-0149(84)90005-0   AbstractWebsite

The bottom waters of the northernmost northeast Atlantic are derived from a dense outflow from the Norwegian Sea through the Faeroe Bank Channel. Near-still mixing increases the salinity and lowers the dissolved oxygen content of the outflow, but when the mixed water later enters the northwest Atlantic through the Charlie-Gibbs Fracture Zone, it is freshened and oxygenated by mixing with the denser, lower-salinity overflow water from Denmark Strait. The end product contributes to a deep tongue of relatively saline, oxygen-rich water that has been traced in other studies throughout much of the World Ocean. This study traces the saline tongue from its origin in the Faeroe Bank Channels to the deep waters south of the Grand Banks. The relatively close coupling of the deep northern North Atlantic with the sea surface in the Greenland, Iceland, and Norwegian seas makes this region potentially responsive to changes introduced at the sea surface, though this study shows no significant temperature and salinity changes in the deep water over the 1957 to 1973 period emphasized in the analysis.

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.

Swift, JH.  1995.  Comparing WOCE and historical temperatures in the deep southeast Pacific. International WOCE Newsletter, WOCE Int'l Project Office. 18:15-17. AbstractWebsite
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Jenkins, WJ, Doney SC, Fendrock M, Fine R, Gamo T, Jean-Baptiste P, Key R, Klein B, Lupton JE, Newton R, Rhein M, Roether W, Sano YJ, Schlitzer R, Schlosser P, Swift J.  2019.  A comprehensive global oceanic dataset of helium isotope and tritium measurements. Earth System Science Data. 11:441-454.   10.5194/essd-11-441-2019   AbstractWebsite

Tritium and helium isotope data provide key information on ocean circulation, ventilation, and mixing, as well as the rates of biogeochemical processes and deep-ocean hydrothermal processes. We present here global oceanic datasets of tritium and helium isotope measurements made by numerous researchers and laboratories over a period exceeding 60 years. The dataset's DOI is https://doi.org/10.25921/clsn-9631, and the data are available at https://www.nodc.noaa.gov/ocads/data/0176626.xml (last access: 15 March 2019) or alternately http://odv.awi.de/data/ocean/jenkins-tritium-helium-data-compilation/ (last access: 13 March 2019) and includes approximately 60 000 valid tritium measurements, 63 000 valid helium isotope determinations, 57 000 dissolved helium concentrations, and 34 000 dissolved neon concentrations. Some quality control has been applied in that questionable data have been flagged and clearly compromised data excluded entirely. Appropriate metadata have been included, including geographic location, date, and sample depth. When available, we include water temperature, salinity, and dissolved oxygen. Data quality flags and data originator information (including methodology) are also included. This paper provides an introduction to the dataset along with some discussion of its broader qualities and graphics.

Schauer, U, Rudels B, Jones EP, Anderson LG, Muench RD, Bjork G, Swift JH, Ivanov V, Larsson AM.  2002.  Confluence and redistribution of Atlantic water in the Nansen, Amundsen and Makarov basins. Annales Geophysicae. 20:257-273.   10.5194/angeo-20-257-2002   AbstractWebsite

The waters in the Eurasian Basin are conditioned by the confluence of the boundary flow of warm, saline Fram Strait water and cold low salinity water from the Barents Sea entering through the St. Anna Trough. Hydrographic sections obtained from RV Polarstern during the summer of 1996 (ACSYS 96) across the St. Anna Trough and the Voronin Trough in the northern Kara Sea and across the Nansen, Amundsen and Makarov basins allow for the determination of the water mass properties of the two components and the construction of a qualitative picture of the circulation both within the Eurasian Basin and towards the Canadian Basin. At the confluence north of the Kara Sea, the Fram Strait branch is displaced from the upper to the lower slope and it forms a sharp front to the Barents Sea water at depths between 100m and greater than 1000m. This front disintegrates downstream along the basin margin and the two components are largely mixed before the boundary current reaches the Lomonosov Ridge. Away from the continental slope, the presence of interleaving structures coherent over wide distances is consistent with low lateral shear. The return flow along the Nansen Gakkel Ridge, if present at all, seems to be slow and the cold water below a deep mixed layer there indicates that the Fram Strait Atlantic water was not covered with a halocline for about a decade. Anomalous water mass properties in the interior of the Eurasian Basin can be attributed to isolated lenses rather than to baroclinic flow cores. Eddies have probably detached from the front at the confluence and migrated into the interior of the basin. One deep (2500m) lens of Canadian Basin water, with an anticyclonic eddy signature, must have spilled through a gap of the Lomonosov Ridge. During ACSYS 96, no clear fronts between Eurasian and Canadian intermediate waters, such as those observed further north in 1991 and 1994, were found at the Siberian side of the Lomonosov Ridge. This indicates that the Eurasian Basin waters enter the Canadian Basin not only along the continental slope but they may also cross the Lomonosov Ridge at other topographic irregularities. A decrease in salinity around 1000 m in depth in the Amundsen Basin probably originates from a larger input of fresh water to the Barents Sea. The inherent density changes may affect the flow towards the Canadian Basin.

Macdonald, RW, Carmack EC, McLaughlin FA, Falkner KK, Swift JH.  1999.  Connections among ice, runoff and atmospheric forcing in the Beaufort Gyre. Geophysical Research Letters. 26:2223-2226.   10.1029/1999gl900508   AbstractWebsite

During SHEBA, thin ice and freshening of the Arctic Ocean surface in the Beaufort Sea led to speculation that perennial sea ice was disappearing [McPhee Ei al., 1998]. Since 1987, we have collected salinity, delta(18)O and Ba profiles near the initial SHEBA site and, in 1997, we ran a section out to SHEBA. Resolving fresh water into runoff and ice melt, we found a large background of Mackenzie River water with exceptional amounts in 1997 explaining much of the freshening at SHEBA. Ice melt went through a dramatic 4-6 m jump in the early 1990s coinciding with the atmospheric pressure field and sea-ice circulation becoming more cyclonic. The increase in sea-ice melt appears to be a thermal and mechanical response to a circulation regime shift. Should atmospheric circulation revert to the more anticyclonic mode, ice conditions can also be expected to revert a! though not necessarily to previous conditions.

Hamann, IM, Swift JH.  1991.  A consistent inventory of water mass factors in the intermediate and deep Pacific Ocean derived from conservative tracers. Deep-Sea Research Part a-Oceanographic Research Papers. 38:S129-S169.   10.1016/S0198-0149(12)80008-2   AbstractWebsite

Estimates of the characteristics and proportional importance of water mass factors are determined by exploratory multivariate Q-mode factor analysis (QMFA) of Pacific Ocean hydrographic data from the region north of 30-degrees-S. The inter-tracer ratios between potential temperature, salinity, the calculated parameters "NO" and "PO" and silicate are used to establish a matrix of similarity coefficients between all station locations. Its rotated eigenvectors ("factors") are viewed as distinct water types of the system. On individual key density surfaces QMFA shows that the spatial distribution of relative contributions from the primary factors can be linked to known or suspected water types and their subsequent spreading. The minor factors reflect smaller perturbations of the dominating ratios. Another QMFA was done in three dimensions by combining all density layers to determine factors derived from diapycnal as well as isopycnal property gradients. Two primary factors represent the opposing vertical temperature and salinity-nutrients gradient: "a deep water melange", which concentrates in the Northeast Pacific (maximum where sigma-1 greater-than-or-equal-to 31.93), and a "subtropical thermocline" factor (maximum on sigma-theta = 25.80) centered in the subtropical gyres. The spatially uneven decrease of relative contribution from a "shallow" factor as one moves down from the upper to the lower thermocline suggests areas where the exchange with the "deeper" factor may be enhanced.

Swift, JH, Aagaard K, Malmberg SA.  1980.  The contribution of the Denmark strait overflow to the deep North Atlantic. Deep-Sea Research Part a-Oceanographic Research Papers. 27:29-42.   10.1016/0198-0149(80)90070-9   AbstractWebsite

Dense water formed in the seas north of the Greenland-Scotland ridge system overflows the ridges and sinks in the North Atlantic. The overflow through Denmark Strait provides the densest component of the Northwest Atlantic Bottom Water, a principal component of the North Atlantic Deep Water. Vertical hydrographic trends in the deep northwest Atlantic differ markedly, however, from those at and north of the Denmark Strait sill. Norwegian Sea Deep Water (NSDW), the densest water mass found north of the sill, contributes less than 10% to the overflow through Denmark Strait. Instead, the principal dense component of this overflow is an intermediate water of arctic origin, at slightly under 34.9% and about 5 T.U. This water is in part formed in winter at the sea surface in the Iceland Sea. The remainder is of more northerly origin, carried southward by the East Greenland Current. Though this intermediate water mass is only slightly less dense than NSDW, its residence time (3 to 4 years) in the waters north of Iceland is an order of magnitude less than that of NSDW. Hence, the deep North Atlantic may be more sensitive to climatological and ecological perturbations than hitherto believed.

Swift, JH, Takahashi T, Livingston HD.  1983.  The contribution of the Greenland and Barents seas to the deep water of the Arctic Ocean. Journal of Geophysical Research-Oceans and Atmospheres. 88:5981-5986.   10.1029/JC088iC10p05981   AbstractWebsite

The deep waters of the Arctic Ocean are traditionally held to be fed by an influx of Norwegian Sea Deep Water (NSDW) via the northward flowing West Spitsbergen Current. Discrete sample and CTD observations obtained from the Greenland-Spitsbergen Passage in August 1981 during the Transient Tracers in the Ocean (TTO) North Atlantic expedition showed a ≈ 100-m-thick layer of modified Greenland Sea Deep Water (GSDW: colder and fresher than NSDW) at 2500 m, spreading northward along the bottom of a deep, unimpeded channel, underneath the NSDW. Since the available data indicate that Arctic Ocean Deep Water (AODW) has a higher salinity than NSDW, mixing of NSDW and GSDW can not produce AODW. Therefore, other sources, such as the peripheral arctic shelf seas, must contribute dense saline water to the Arctic Ocean. Concentrations of 137Cs and 90Sr observed in AODW are greater than those observed in GSDW and NSDW. The concentrations of these radionuclides on the Barents Sea shelf are sufficiently high and in the correct relative proportions to support this proposition.