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    Summary of linear decadal trends (red lines) and pattern of changes in the following: (a) Anomalies in Arctic sea ice extent from satellite passive microwave observations [based on procedures in Comiso and Nishio (2008)]. Uncertainties are discussed in the text. (b) Multiyear sea ice coverage on 1 Jan from analysis of the Quick Scatterometer (QuikSCAT) time series (Kwok 2009); gray band shows uncertainty in the retrieval. (c) Sea ice thickness from submarine (blue), satellites (black) (Kwok and Rothrock 2009), and in situ/electromagnetic (EM) surveys (circles) (Haas et al. 2008); trend in submarine ice thickness is from multiple regression of available observations within the data release area (Rothrock et al. 2008). Error bars show uncertainties in observations. (d) Anomalies in buoy (Rampal et al. 2009) and satellite-derived sea ice drift speed (Spreen et al. 2011). (e) Length of melt season [updated from Markus et al. (2009)]; gray band shows the basinwide variability. From Vaughan et al. (2013).

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    Norbert Untersteiner (1926–2012)

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    Schematic diagram showing oceanic domains (shelves vs basins) and key processes (lateral and vertical) affecting ocean heat fluxes in the Arctic Ocean. Refer to the text for details about SML, NSTM, PW, LH, AW, and DW. Note that the areas of shelf and basin are roughly equal and that PW is largely confined within the Canadian basin. Distinct ice features include 1) landfast ice, 2) ridged (stamukhi) ice, 3) flaw lead zones between landfast and floe ice, 4) first-year ice over shelf regions, 5) first-year ice over basins, and 6) multiyear and ridged ice over basins. Oceanic processes include 7) formation of the NSTM, 8) free and forced convection, 9) the subduction and circulation of PW, 10) the subduction and circulation of AW, 11) coastal-trapped flows of river and low-salinity inflows, 12) wind forcing, 13) the drainage of shelf-modified waters to depth, 14) mixing due to tides and internal waves, 15) mixing due to shear, 16) double diffusion, 17) thermohaline intrusions, and 18) shelf-break upwelling. The polar vortex is schematically shown by the height of the 850-mb surface and is bounded by the polar jet stream (PJS). The regional variation in solar angle by latitude and season is shown by the angles α1 and α2. Application of logistics and specific instrumentation (e.g., ships, ice camps, satellite remote sensing, gliders AUVs, ITPs) will depend critically on matching regional and seasonal challenges with appropriate technologies.

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    Circulation of the surface water (blue), intermediate Pacific Water (pink/blue), and Atlantic Water (red) of the Arctic Ocean.

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    Double-diffusive staircases and heat fluxes in the Arctic Ocean. 1) Summary diagram for a conductivity–temperature–depth (CTD) profile collected in autumn 2012 at 77°N, 140°W in the Beaufort Sea. (a) Codependence of potential temperature and salinity, with blue indicating a subdomain containing staircase signatures and red indicating one with interleaving signatures. (b) Temperature and salinity profiles in the staircase region, showing roughly homogeneous layers a few meters thick, separated by much thinner interfaces. (c) Temperature and salinity profiles in the interleaving zone, revealing an alternating-sign pattern in temperature and salinity gradients on a scale of a few tens of meters, along with some thinner layers within the presumed intrusions. 2) Map of heat flux (W m–2) estimated by averaging over the 200–300-m-deep thermohaline staircases from the ITPs (Timmermans et al. 2008a). 3) Microstructure observations for a typical station from the Laptev Sea slope region. (a) Temperature is shown by shading and salinity is shown by the thick line. (b) Estimates of turbulent heat flux derived from microstructure measurements. (c) Double-diffusive heat flux derived from microstructure measurements of temperature and salinity. For further details, see Lenn et al. (2009). Horizontal axes in (b) and (c) use logarithmic scale.

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    Ice-mass buoy observations reveal the important role of bottom ice melt in areas of dramatic sea ice loss. Inset: 2008 observations placed in a long-term framework, demonstrating the major increase in bottom melt [modified from Perovich et al. (2011)].

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    (top) Potential temperature θ (°C) and (bottom) salinity S along the ITP drifts. (a) Canadian basin. (b) Eastern and central Eurasian basin, ITP-36/-37 drifts, 2009/10. Horizontal axis for both ITPs shows profile number complemented by approximate time. White segments indicate missing data. (right) Black solid line (ITP-37) shows the depth of the upper mixed layer; (bottom right) black broken line (ITP-37, salinity) shows the depth of the cold halocline layer (CHL) base. (c) Central Nansen basin. For all insets: the ranges of parameters used for color maps are shown in white inserted windows; the first (last) color scale is used for values less (more) than the identified range. Data for (a) and (b) are available from www.whoi.edu/itp.

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    Main map: mean barotropic tidal speed (m s–1; color scale on right), following Padman and Erofeeva (2004). White contours are 500-, 1000-, 2000-, and 3000-m isobaths. Inset: 25-day record of (from top to bottom) temperature (T), salinity (S), buoyancy frequency (N), turbulent dissipation rate (ε), and water depth as functions of time (t) and depth (z) as the Coordinated Eastern Arctic Experiment (CEAREX) Oceanography “O” Camp drifted across the Yermak Plateau in 1989; see Padman and Dillon (1991) for details. Tides in this region are primarily diurnal, seen in T(t, z) and S(t, z). (bottom) Tidal amplitudes vary with both position relative to topography and time within the approximately 14-day spring–neap cycle owing to the superposition of major tidal constituents. Plot of ε(t, z) shows tidal modulation of mixing rates in the pycnocline and in the SML at the base of the sea ice.

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Toward Quantifying the Increasing Role of Oceanic Heat in Sea Ice Loss in the New Arctic

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  • 1 Fisheries and Oceans Canada, Sidney, British Columbia, Canada, and College of Natural Science and Mathematics, University of Alaska Fairbanks, Fairbanks, Alaska
  • | 2 International Arctic Research Center, and College of Natural Science and Mathematics, University of Alaska Fairbanks, Fairbanks, Alaska
  • | 3 Earth and Space Research, Corvallis, Oregon
  • | 4 Geophysical Institute, University of Bergen and Bjerknes Centre for Climate Research, Bergen, Norway
  • | 5 Los Alamos National Laboratory, Los Alamos, New Mexico
  • | 6 Oregon State University, Corvallis, Oregon
  • | 7 Hakai Institute, Heriot Bay, British Columbia, Canada
  • | 8 Dalhousie University, Halifax, Nova Scotia, Canada
  • | 9 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California
  • | 10 Dalhousie University, Halifax, Nova Scotia, Canada
  • | 11 Fisheries and Oceans Canada, Sidney, British Columbia, Canada
  • | 12 Cold Regions Research and Engineering Laboratory, Hanover, New Hampshire
  • | 13 Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, Colorado
  • | 14 Dalhousie University, Halifax, Nova Scotia, Canada
  • | 15 Yale University, New Haven, Connecticut
  • | 16 Woods Hole Oceanographic Institution, Woods Hole, Massachusetts
  • | 17 Dalhousie University, Halifax, Nova Scotia, Canada
  • | 18 Center for Climatic Research, University of Wisconsin–Madison, Madison, Wisconsin
  • | 19 Institute of Marine Science, University of Alaska Fairbanks, Fairbanks, Alaska
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