Fig. 1.
Map of the Nordic Seas. The grey lines show (from light to dark) the 500, 1000, 1500, 2000, 3000 and 4000 m isobaths. The bold black contour outlines our definition of the Greenland Sea gyre, and the green x marks the position of the Faroe-Shetland Channel hydrographic time series. The generalised circulation pattern in the region is shown with red and blue arrows indicating warm and cold currents, respectively.
Fig. 2.
Interpolated time series of (a) salinity, (b) potential temperature (θ, °C), (c) oxygen (μmol kg−1) in the Greenland Sea gyre. The black dots indicate the wintertime (February–April) average profiles for salinity and θ, and the annual average profile for oxygen.
Fig. 3.
Figure showing the temporal evolution of winter mean (circles) salinity and potential temperature (θ, °C) for three different depths in the Greenland Sea gyre. The shaded area indicates one standard deviation of the mean of all data in each year.
Table 1.
Trends in winter (February–April) temperature and salinity for three different depth levels over the years 1985 to 2016. To limit the effect of sampling bias, the regression is based on the mean of winter observations each year. The uncertainty is estimated using a Monte Carlo simulation (1000 runs) of possible slopes within the one standard deviation confidence interval of each year (as shown in Fig. 3). Note that all regressions are statistically significant with a p-value of zero for a Student’s t-test.
Fig. 4.
Diagram of wintertime (February–April): (a) potential temperature and salinity; (b) potential temperature and oxygen. All points are annual averages over 500–1500 m in the Greenland Sea gyre in period 1985–2016. The arrow in (b) indicates the direction of change if only the solubility of oxygen changed.
Fig. 5.
Time series of (a) oxygen inventory (mol m−2) integrated over the top 2000 m of the Greenland Sea gyre; (b) maximum wintertime mixed-layer depths (m) in the Greenland Sea gyre. For both (a) and (b) the error bars indicate one standard deviation of the annual average.
Fig. 6.
Time series of (a) potential temperature anomalies and (b) salinity anomalies in the core of Atlantic Water in the Faroe-Shetland Channel (black bars), and the surface waters (<150 m) of the Greenland Sea gyre (red line).