Fig. 2: North Atlantic Oscillation (NAO)-related atmospheric thermodynamic impacts on an interdecadal scale.
From: Recent slowing of Arctic sea ice melt tied to multidecadal NAO variability
a summer (June-July-August, JJA) 500 hPa geopotential height (HGT, colored, interval: 2, unit: m) regressed onto the standardized September Arctic sea ice (ASI) index, b summer (JJA) 500 hPa geopotential height (HGT, colored, interval: 2, unit: m), c lower-tropospheric (1000-700 hPa) air temperature (AT, colored, interval: 0.1, unit: K), d total column water vapour (WV, colored, interval: 0.08, unit: kg m−2), e downwelling longwave radiation at surface (DLR, colored, interval: 0.4, unit: W m−2) and f September sea ice concentration (SIC, colored, interval: 2, unit: %) anomalies regressed onto the standardized summer (JJA) NAO index. The white dots indicate statistically significance at p < 0.1. Yellow dashed boxes mark the areas of 66.5°–90° N, 90°–40° W. g The time series of standardized September ASI index (dashed red curve), the summer (JJA) NAO index (dashed blue curve), AT index (dashed grey curve), WV index (dashed yellow curve) and DLR index (dashed purple line) from 1955 to 2018. The values r and p denote the correlation coefficients and significant levels between the ASI/NAO index and AT index, between the ASI/NAO index and WV index, between the ASI/NAO index and DLR index, and between the ASI index and NAO index. For convenience, the NAO index and DLR index have been multiplied by one-third. The ASI index is derived from Hadley. These data have been de-trended and subjected to an 11-year sliding average. The atmospheric reanalysis data are derived from ERA5 (European Centre for Medium-Range Weather Forecasts Reanalysis v5) atmospheric reanalysis dataset.
