Spatial variability of climate and past atmospheric circulation patterns from central West Antarctic glaciochemistry

Atmospheric circulation patterns and the spatial variability of atmospheric chemistry and moisture transport in central West Antarctica are investigated using new 40 year long (1954–1994 A.D.) glaciochemical and accumulation rate records developed from four firn cores from this region. The core sites lie on a 200 km traverse from 82° 22′ S, 119° 17′ W to 81° 22′ S, 107° 17′ W. The glaciochemical records represent the major ionic species present in Antarctic snow: Na+, K+, Mg2+, Ca2+, Cl−, NO3−, and SO42−. High spatial variability appears in comparisons of full record averages and poor intersite linear correlation results. Accumulation rates show 50–100% changes over distances of 50–100 km and sea‐salt concentrations drop by 50% between the middle two sites. One likely contributor to the high variability seen at this spatial scale is variability in synoptic‐ and finer‐scale meteorology. Empirical orthogonal function (EOF) analysis shows that 80% or more of the variance in site chemistry can be attributed to two types of air masses: winter season air (50–70% of site variance) with a strong marine signature (heavy loading of sea‐salt species) and summer season air (21% of the variance), marked by marine biogenic non‐sea‐salt SO4 plus NO3. This pattern of winter and summer regimes appears at other West Antarctic sites suggesting it may apply to the entire region. We show that a general picture of the patterns of variability in West Antarctica can best be drawn by using an analysis technique that fully exploits high resolution, multiparameter, multisite data sets

Sea level pressure variability in the Amundsen Sea region inferred from a West Antarctic glaciochemical record

Using European Center for Medium‐Range Weather Forecasts (ECMWF) numerical operational analyses, sea ice extent records, and station pressure data, we investigate the influence of sea level pressure variability in the Amundsen Sea region on a West Antarctic (Siple Dome) glaciochemical record. Empirical orthogonal function analysis of the high‐resolution Siple Dome multivariate ice core chemical time series record (SDEOF1) documents lower tropospheric transport of sea‐salt aerosols to the site. During 1985–1994 the SDEOF1 record of high (low) aerosol transport corresponds to anomalously low (high) sea level pressure (SLP) in the Amundsen Sea region. Spatial correlation patterns between ECMWF monthly SLP fields and the annual SDEOF1 record suggest that a majority of sea‐salt aerosol is transported to Siple Dome during spring (September, October, and November). Analysis of zonal and meridional wind fields supports the SLP/SDEOF1 correlation and suggests the SDEOF1 record is sensitive to changes in regional circulation strength. No relationship is found between sea ice extent and the SDEOF1 record for the period 1973–1994. To investigate the SDEOF1 record prior to ECMWF coverage, a spring transpolar index (STPI) is created, using normalized SLP records from the New Zealand and South America/Antarctic Peninsula sectors, and is significantly correlated (at least 95% c.l.) with the SDEOF1 record on an annual (r = 0.32, p \u3c 0.001) and interannual (3 years; r = 0.51, p \u3c 0.001) basis. Dominant periodicities (3.3 and 7.1 years) in the annual SDEOF1 record (1890–1994 A.D.) suggest that a portion of the recorded interannual variability may be related tropical/extratropical ENSO teleconnections. Changes in the periodic structure of the full (850–1994 A.D.) Siple Dome record suggests a shift in SLP forcing during the Little Ice Age (∼1400–1900 A.D.) interval

Bipolar Changes in Atmospheric Circulation During the Little Ice Age

Annually dated ice cores from Siple Dome, West Antarctica, and central Greenland indicate that meridional atmospheric circulation intensity increased in the polar South Pacific and North Atlantic at the beginning (∼1400 A.D.) of the most recent Holocene rapid climate change event, the Little Ice Age (LIA). As deduced from chemical concentrations at these core sites, the LIA was characterized by substantial meridional circulation strength variability, and this variability persists today despite strong evidence for an end to LIA cooling. Thus, increased late 20th century storm variability may be in part a result of the continuation of these climatic fluctuations