The signatures of large‐scale patterns of atmospheric variability in Antarctic surface temperatures

Abstract

We investigate the impact that the four principal large-scale patterns of Southern Hemisphere (SH) atmospheric circulation variability have on Antarctic surface air temperature (SAT): (1) the southern baroclinic annular mode (BAM), which is associated with variations in extratropical storm amplitude; (2) the Southern Annular Mode (SAM), associated with latitudinal shifts in the midlatitude jet; and (3) the two Pacific-South American patterns (PSA1 and PSA2), which are characterized by wave trains originating in the tropical Pacific that extend across the SH extratropics. A key aspect is the use of 35 years of daily observations and reanalysis data, which affords a sufficiently large sample size to assess the signatures of the circulation patterns in both the mean and variability of daily mean SAT anomalies. The BAM exerts the weakest influence on Antarctic SAT, albeit it is still important over select regions. Consistent with previous studies, the SAM is shown to influence SAT across most of the continent throughout the year. The PSA1 also affects SAT across almost all of Antarctica. Regionally, both PSA patterns can exert a greater impact on SAT than the SAM but also have a significantly weaker influence during summer, reflecting the seasonality of the SH response to El Niño-Southern Oscillation. The SAM and PSA patterns have distinct signatures in daily SAT variance that are physically consistent with their signatures in extratropical dynamic variability. The broad-scale climate linkages identified here provide benchmarks for interpreting the Antarctic climate response to future changes in tropical sea surface temperatures, ozone recovery, and greenhouse gas increases.

The Ross Sea Dipole – temperature, snow accumulation and sea ice variability in the Ross Sea region, Antarctica, over the past 2700 years

“…The persistent positive, summer trend of the SAM (decreasing pressure over Antarctica) has been linked to stratospheric ozone depletion and an increase in atmospheric greenhouse gas concentration Thompson et al, 2011). The positive SAM is associated with above-average warming of the Antarctic Peninsula, cooler conditions over East Antarctica due to a reduced poleward pressure gradient and thus diminished transport of heat and moisture, and a reduction in katabatic flow Marshall and Thompson, 2016;Thompson and Solomon, 2002a). While the positive summer SAM trend (also weakly expressed during autumn) along the Antarctic margin is generally associated with an equatorward heat flux, the western Ross Sea is one of two regions (the Weddell Sea being the other) to experience an anomalous poleward heat flux (Marshall and Thompson, 2016) that transports heat and moisture across the Ross Ice Shelf.…”

“…The positive SAM is associated with above-average warming of the Antarctic Peninsula, cooler conditions over East Antarctica due to a reduced poleward pressure gradient and thus diminished transport of heat and moisture, and a reduction in katabatic flow Marshall and Thompson, 2016;Thompson and Solomon, 2002a). While the positive summer SAM trend (also weakly expressed during autumn) along the Antarctic margin is generally associated with an equatorward heat flux, the western Ross Sea is one of two regions (the Weddell Sea being the other) to experience an anomalous poleward heat flux (Marshall and Thompson, 2016) that transports heat and moisture across the Ross Ice Shelf. No such pattern is observed for regional surface air temperature (SAT) (Marshall and Thompson, 2016), which might be masked by the influence of regional sea ice variability on local temperatures.…”

“…While the positive summer SAM trend (also weakly expressed during autumn) along the Antarctic margin is generally associated with an equatorward heat flux, the western Ross Sea is one of two regions (the Weddell Sea being the other) to experience an anomalous poleward heat flux (Marshall and Thompson, 2016) that transports heat and moisture across the Ross Ice Shelf. No such pattern is observed for regional surface air temperature (SAT) (Marshall and Thompson, 2016), which might be masked by the influence of regional sea ice variability on local temperatures. The positive SAM has been shown to contribute at least partially to an increase in total Antarctic sea ice, while a negative SAM has been associated with a reduced sea ice (Ferreira et al, 2015;Holland et al, 2017;Bintanja et al, 2013;Kohyama and Hartmann, 2015;Turner et al, 2017).…”

The impacts of El Niño on the observed sea ice budget of West Antarctica

“…During the El Niño phase of ENSO, a Rossby wave train of alternating positive and negative geopotential height anomalies becomes established from the central Pacific to the ASL region, often described as the positive polarity of the Pacific-South American (PSA-1) teleconnection pattern [Mo and Higgins, 1998;Mo and Paegle, 2001;Irving and Simmonds, 2016]. This is associated with a weakening of the ASL [Marshall and Thompson, 2016;Turner, 2004], resulting in increased sea ice in the Bellingshausen Sea and decreased sea ice in the Ross Sea [Kwok and Comiso, 2002;Dash et al, 2013;Kwok et al, 2016]. This tropical teleconnection and its influence on the Antarctic have been found to be enhanced when El Niño coincides with the negative phase of the Southern Annular Mode (SAM) [Fogt et al, 2011[Fogt et al, , 2012 • Supporting Information S1…”

Can Temperature Extremes in East Antarctica be Replicated from ERA Interim Reanalysis?

“…If such temperature extremes occurred in Antarctica, there would be even greater worldwide effects, since Antarctica has much greater heat reserves. On the other hand, mass loss owing to sublimation and erosion of snow by the wind has a potentially large impact on the surface mass balance (van den Broeke et al, 1999), prolonged katabatic wind events affect the near-surface climate, summer melt percolation and changes in the stress field due to shelf removal play a major role in glacier dynamics, and extreme snowmelt events have a great impact on ice shelf disintegration (Cape et al, 2015;Marshall and Thompson, 2016;Scambos et al, 2004;Shepherd et al, 2012).…”