Figure 1.
Location map of Arctic Ocean underway and discrete inorganic carbon data.
Locations are shown for the HLY1002 and HLY1102 cruises, as well as previous work. Previous data are from the Carbon Dioxide Information Analysis Center (http://cdiac.ornl.gov/oceans/datmet.html), Japan Agency for Marine Earth Science and Technology (http://www.godac.jamstec.go.jp/dataportal/viewer.htm), and BioChem (http://www.meds-sdmm.dfo-mpo.gc.ca/BioChem/biochem-eng.htm). Digital bathymetry is from the International Bathymetric Chart of the Arctic Ocean [48]. The highlighted sector is shown in subsequent figures.
Table 1.
Methods used to measure carbonate system parameters on the HLY1002 (2010) and HLY1102 (2011) cruises.
Figure 2.
Sensitivity of mixing-model output (fSW, fSIM, and fMW) to variations in assumed end-member compositions.
Upper panels show the effect of varying end-member δ18O by 10% of the observed δ18O range: i.e., by ±0.1(δ18Omax−δ18Omin) = ±0.2‰. Lower panels show the effect of varying end-member S by 10% of the observed S range: i.e., by ±0.1(Smax−Smin). Model sensitivity is calculated for a hypothetical sample with S and δ18O equal to the mid-range values of the combined HLY1002 and HLY1102 data sets: Smodel = Smin+½(range S) and δ18Omodel = δ18Omin+½(range δ18O).
Figure 3.
Aragonite saturation state, Ωa, calculated from discrete samples and from underway MICA readings.
(A) Cross plot of discrete sample values with nearest-neighbor MICA values. (B) Map of 2010 discrete sample values. (C) Map of 2010 MICA values.
Table 2.
Regional median values (and ranges) for 2011 surface water data and mixing-model output.
Table 3.
Dunn’s Method Q-statistic results for pairwise multiple comparisons of the four Arctic Ocean regions.
Figure 4.
Surface salinity in the western Arctic Ocean.
(A) Map showing August mean salinity (through 1997) at 10 m depth from the World Ocean Atlas 1998 [51]. Data provided by Physical Sciences Division, Earth System Research Laboratory, NOAA (http://www.esrl.noaa.gov/psd/). (B) Map of HLY1002 (2010) and HLY1102 (2011) discrete sample salinities.
Figure 5.
Surface water aragonite saturation state (Ωa) and ice cover in the western Arctic Ocean.
(A) Canadian Basin (outlined in blue) and area of surface Ωa undersaturation during 2010–2011 (red). (B) HLY1002 aragonite saturation state. (C) HLY1102 aragonite saturation state. Maps (B) and (C) also show average sea ice concentration (% ice cover) for August 2010 and September 2011, respectively [70]. The Makarov Basin, Sever Spur, and coastal Beaufort Sea regions are encircled in red; the remaining data points are assigned to the Canada Basin region. All Ωa values are calculated from discrete sample data.
Figure 6.
Surface pCO2 in the western Arctic Ocean.
(A) HLY1002. (B) HLY1102. The data points show underway pCO2 values recorded at locations where discrete surface water samples were collected. The maps also show average sea ice concentration (% ice cover) for August 2010 and September 2011, respectively [70].
Figure 7.
Modeled freshwater fractional contributions to surface waters of the western Arctic Ocean.
(A) Fraction of sea ice melt, fSIM. (B) Fraction of meteoric water, fMW. The maps also show average sea ice concentration (% ice cover) during September 2011 [70].
Table 4.
Spearman rank-order correlations between the Arctic Ocean regions.
Figure 8.
Aragonite saturation state and freshwater contributions in regions of the western Arctic Ocean.
Comparison of aragonite saturation state (Ωa) to freshwater source fractions (fSIM plotted on x-axis, fMW coded to point color). Symbol shapes identify the basin, where the data were collected. Ellipses outline general data clusters from each region.
Figure 9.
Modeled Ωa:fSIM for conservative mixing of seawater and sea ice meltwater.
(A) Effect of variable pCO2 with constant fMW = 0.18. (B) Effect of variable fMW with constant pCO2 = 372.6 µatm. The values of the constants are equal to the mid-range values observed during the 2011 cruise. The gray points show the data from Figure 8. For the freshwater end-member [33], [35], [39], [55], TAMW = 1000 µmol kg−1, SFW = 0, and TCO2MW = 940 µmol kg−1. For the sea ice meltwater end-member [40], [71], TASIM = 540 µmol kg−1, SSIM = 4, and TCO2SIM = 300 µmol kg−1. Atlantic seawater is characterized according to mean values observed at the thermocline in the HLY1102 station data, 250–400 m depth: TASW = 2318.5 µmol kg−1, SSW = 34.92, and TCO2SW = 2156.6 µmol kg−1). All models are calculated at a seawater T of −1.47°C (median value of the HLY1102 data set).