The semi-annual oscillation and Antarctic climate. Part 1: influence on near surface temperatures (1957–79)

1998 ◽  
Vol 10 (2) ◽  
pp. 175-183 ◽  
Author(s):  
Michiel R. Van Den Broeke
Keyword(s):  
Surface Pressure ◽  
Meridional Circulation ◽  
Second Harmonic ◽  
Temperature Inversion ◽  
East Antarctica ◽  
Temperature Cycle ◽  
Near Surface ◽  
Antarctic Plateau ◽  
Surface Temperatures ◽  
The Antarctic

We studied the influence of the semi-annual oscillation (SAO) on near-surface temperatures in Antarctica, using observations of 27 stations that were operational during (part of) the period 1957–79. For the annual cycle of surface pressure, the second harmonic explains 17–36% of the total variance on the Antarctic Plateau, 36–68% along the East Antarctic coast and almost 80% on the west coast of the Peninsula, and decreases further to the north. As a result of the amplification of the wave-3 structure of the circulation around Antarctica, a significant modification of the seasonal cooling is observed at many stations. The magnitude of this modification is largely determined by the strength of the temperature inversion at the surface: the percentage of the variance explained by the second harmonic of the annual temperature cycle is then largest on the Antarctic Plateau (11–18%), followed by the large ice shelves and coastal East Antarctica (6–12%) and stations at or close to the Peninsula (0–5%). A significant coupling between the half-yearly wave in surface pressure and that in surface temperature is found for coastal East Antarctica, which can be directly explained by the changes in meridional circulation brought about by the SAO. We show that the coupling of Antarctic temperatures to the meridional circulation is not only valid on the seasonal time scale of the SAO, but probably also on daily and interannual time scales. This has important implications for the interpretation of time series of Antarctic temperatures, a problem that will be addressed in part 2 of this paper.

scholarly journals An Assessment of ERA5 Reanalysis for Antarctic Near-Surface Air Temperature

Atmosphere ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 217
Author(s):  
Jiangping Zhu ◽  
Aihong Xie ◽  
Xiang Qin ◽  
Yetang Wang ◽  
Bing Xu ◽  
...  
Keyword(s):  
Linear Relationship ◽  
Antarctic Peninsula ◽  
Austral Summer ◽  
Correlation Coefficients ◽  
East Antarctica ◽  
West Antarctica ◽  
Austral Spring ◽  
Reanalysis Dataset ◽  
Near Surface ◽  
The Antarctic

The European Center for Medium-Range Weather Forecasts (ECMWF) released its latest reanalysis dataset named ERA5 in 2017. To assess the performance of ERA5 in Antarctica, we compare the near-surface temperature data from ERA5 and ERA-Interim with the measured data from 41 weather stations. ERA5 has a strong linear relationship with monthly observations, and the statistical significant correlation coefficients (p < 0.05) are higher than 0.95 at all stations selected. The performance of ERA5 shows regional differences, and the correlations are high in West Antarctica and low in East Antarctica. Compared with ERA5, ERA-Interim has a slightly higher linear relationship with observations in the Antarctic Peninsula. ERA5 agrees well with the temperature observations in austral spring, with significant correlation coefficients higher than 0.90 and bias lower than 0.70 °C. The temperature trend from ERA5 is consistent with that from observations, in which a cooling trend dominates East Antarctica and West Antarctica, while a warming trend exists in the Antarctic Peninsula except during austral summer. Generally, ERA5 can effectively represent the temperature changes in Antarctica and its three subregions. Although ERA5 has bias, ERA5 can play an important role as a powerful tool to explore the climate change in Antarctica with sparse in situ observations.

scholarly journals The Weddell Sea region: an important precipitation channel to the interior of the Antarctic ice sheet as revealed by glaciochemical investigation of surface snow along the longest trans-Antarctic route

1999 ◽  
Vol 29 ◽  
pp. 55-60 ◽  
Author(s):  
Qin Dahe ◽  
Paul A. Mayewski ◽  
Ren Jiawen ◽  
Xiao Cunde ◽  
Sun Junying
Keyword(s):  
Ice Sheet ◽  
Weddell Sea ◽  
Sea Salt ◽  
East Antarctica ◽  
Antarctic Ice Sheet ◽  
Air Masses ◽  
Antarctic Plateau ◽  
Salt Ions ◽  
Surface Snow ◽  
The Antarctic

AbstractGlaciochemical analysis of surface snow samples, collected along a profile crossing the Antarctic ice sheet from the Larsen Ice Shelf, Antarctic Peninsula, via the Antarctic Plateau through South Pole, Vostok and Komsomolskaya to Mirny station (at the east margin of East Antarctica), shows that the Weddell Sea region is an important channel for air masses to the high plateau of the Antarctic ice sheet (>2000 m a.s.l.). This opinion is supported by the following. (1) The fluxes of sea-salt ions such as Na+, Mg2 + and CF display a decreasing trend from the west to the east of interior Antarctica. In |eneral, as sea-salt aerosols are injected into the atmosphere over the Antarctic ice sheet from the Weddell Sea, large aerosols tend to decrease. For the inland plateau, few large particles of sea-salt aerosol reach the area, and the sea-salt concentration levels are low (2) The high altitude of the East Antarctic plateau, as well as the polar cold high-pressure system, obstruct the intrusive air masses mainly from the South Indian Ocean sector. (3) For the coastal regions of the East Antarctic ice sheet, the elevation rises to 2000 m over a distance from several to several tens of km. High concentrations of sea salt exist in snow in East Antarctica but are limited to a narrow coastal zone. (4) Fluxes of calcium and non-sea-salt sulfate in snow from the interior plateau do not display an eastward-decreasing trend. Since calcium is mainly derived from crustal sources, and nssSO42- is a secondary aerosol, this again confirms that the eastward-declining tendency of sea-salt ions indicates the transfer direction of precipitation vapor.

scholarly journals Antarctic 20th Century Accumulation Changes Based on Regional Climate Model Simulations

2010 ◽  
Vol 2010 ◽  
pp. 1-14 ◽  
Author(s):  
Klaus Dethloff ◽  
Ksenia Glushak ◽  
Annette Rinke ◽  
Dörthe Handorf
Keyword(s):  
Regional Climate Model ◽  
Climate Model ◽  
Regional Climate ◽  
Reanalysis Data ◽  
Horizontal Resolution ◽  
East Antarctica ◽  
Transient Pressure ◽  
Near Surface ◽  
Surface Mass ◽  
The Antarctic

The regional climate model HIRHAM has been applied to Antarctica driven at the lateral and lower boundaries by European Reanalysis data ERA-40 for the period 1958–1998. Simulations over 4 decades, carried out with a horizontal resolution of 50 km, deliver a realistic simulation of the Antarctic atmospheric circulation, synoptic-scale pressure systems, and the spatial distribution of precipitation minus sublimation (P-E) structures. The simulated P-E pattern is in qualitative agreement with glaciological estimates. The estimated (P-E) trends demonstrate surfacemass accumulation increase at the West Antarctic coasts and reductions in parts of East Antarctica. The influence of the Antarctic Oscillation (AAO) on the near-surface climate and the surface mass accumulation over Antarctica have been investigated on the basis of ERA-40 data and HIRHAM simulations. It is shown that the regional accumulation changes are largely driven by changes in the transient activity around the Antarctic coasts due to the varying AAO phases. During positive AAO, more transient pressure systems travelling towards the continent, and Western Antarctica and parts of South-Eastern Antarctica gain more precipitation and mass. Over central Antarctica the prevailing anticyclone causes a strengthening of polar desertification connected with a reduced surface mass balance in the northern part of East Antarctica.

scholarly journals New Reconstruction of Antarctic Near-Surface Temperatures: Multidecadal Trends and Reliability of Global Reanalyses*,+

2014 ◽  
Vol 27 (21) ◽  
pp. 8070-8093 ◽  
Author(s):  
Julien P. Nicolas ◽  
David H. Bromwich
Keyword(s):  
Austral Summer ◽  
Southern Annular Mode ◽  
East Antarctica ◽  
Temperature Record ◽  
West Antarctica ◽  
Amundsen Sea ◽  
Near Surface ◽  
Weather Forecasts ◽  
Temperature Trends ◽  
Surface Temperatures

Abstract A reconstruction of Antarctic monthly mean near-surface temperatures spanning 1958–2012 is presented. Its primary goal is to take advantage of a recently revised key temperature record from West Antarctica (Byrd) to shed further light on multidecadal temperature changes in this region. The spatial interpolation relies on a kriging technique aided by spatiotemporal temperature covariances derived from three global reanalyses [the European Centre for Medium-Range Weather Forecasts (ECMWF) Interim Re-Analysis (ERA-Interim), Modern-Era Retrospective Analysis for Research and Applications (MERRA), and Climate Forecast System Reanalysis (CFSR)]. For 1958–2012, the reconstruction yields statistically significant annual warming in the Antarctic Peninsula and virtually all of West Antarctica, but no significant temperature change in East Antarctica. Importantly, the warming is of comparable magnitude both in central West Antarctica and in most of the peninsula, rather than concentrated either in one or the other region as previous reconstructions have suggested. The Transantarctic Mountains act for the temperature trends, as a clear dividing line between East and West Antarctica, reflecting the topographic constraint on warm air advection from the Amundsen Sea basin. The reconstruction also serves to highlight spurious changes in the 1979–2009 time series of the three reanalyses that reduces the reliability of their trends, illustrating a long-standing issue in high southern latitudes. The study concludes with an examination of the influence of the southern annular mode (SAM) on Antarctic temperature trends. The results herein suggest that the trend of the SAM toward its positive phase in austral summer and fall since the 1950s has had a statistically significant cooling effect not only in East Antarctica (as already well documented) and but also (only in fall) in West Antarctica.

scholarly journals Spatial and Temporal Variations of Snow Chemistry in Terre Adélie (East Antarctica)

1985 ◽  
Vol 7 ◽  
pp. 20-25 ◽  
Author(s):  
Michel Legrand ◽  
Robert J. Delmas
Keyword(s):  
Ion Chromatography ◽  
Temporal Variations ◽  
Sea Salt ◽  
East Antarctica ◽  
Snow Chemistry ◽  
Antarctic Plateau ◽  
Time Period ◽  
Terre Adélie ◽  
The Mean ◽  
The Antarctic

The chemistry of recently deposited snow sampled in 1982–83 along a 430 km coast-interior traverse in Terre Adelie, East Antarctica, is reported. In addition, three firn samples, covering the same time period (1959 to 1969) and collected on the traverse at D 55, D 80 and Dome C stations, respectively at 200, 430 and 1070 km from the sea, are also studied. Concentrations of major soluble impurities (H+, , Na+, K+, Cl−, and ) were determined by ion chromatography (except H+ which was titrated) on more than 200 samples. Conditions of sampling and analysis were carefully controlled in order to avoid contamination problems. A balanced ionic budget was generally obtained for each of the samples. For stations occupying an intermediary position between the coastal areas and the central Antarctic plateau, our results demonstrate that the two major impurities are H2SO4 and HNO3. HCl is also present, but at a lower level of concentration; the sea-salt contribution is dominant only at the most coastal sites (within 40 km) of the sea. The degree of neutralization of the snow acidity by NH3 is always very low as indicated by the values of content. The mean concentrations of H2SO4 along the traverse are relatively constant whereas an increase of the HNO3 concentrations is observed when going inland. It decreases, however, in most central areas. These results are discussed in relation to the glaciochemical data published for other locations on the Antarctic plateau, in particular the sulphate concentrations which depend strongly on explosive volcanic activity.

scholarly journals Changes in Antarctic temperature, wind and precipitation in response to the Antarctic Oscillation

2004 ◽  
Vol 39 ◽  
pp. 119-126 ◽  
Author(s):  
Michiel R. van den Broeke ◽  
Nicole P. M. van Lipzig
Keyword(s):  
Climate Model ◽  
Weddell Sea ◽  
East Antarctica ◽  
Antarctic Oscillation ◽  
West Antarctica ◽  
Ice Shelf ◽  
Near Surface ◽  
Ross Ice Shelf ◽  
Temperature And Precipitation ◽  
The Antarctic

AbstractOutput of a 14 year integration with a high-resolution (55 km ×55 km) regional atmospheric climate model is used to study the response of Antarctic near-surface climate to the Antarctic Oscillation (AAO), the periodical strengthening and weakening of the circumpolar vortex in the Southern Hemisphere. In spite of the relatively short record, wind, temperature and precipitation show widespread and significant AAO-related signals. When the vortex is strong (high AAO index), northwesterly flow anomalies cause warming over the Antarctic Peninsula (AP) and adjacent regions in West Antarctica and the Weddell Sea. In contrast, cooling occurs in East Antarctica, the eastern Ross Ice Shelf and parts of Marie Byrd Land. Most of the annual temperature signal stems from the months March–August. The spatial distribution of the precipitation response to changes in the AAO does not mirror temperature changes but is in first order determined by the direction of flow anomalies with respect to the Antarctic topography. When the vortex is strong (high AAO index), the western AP becomes wetter, while the Ross Ice Shelf, parts of West Antarctica and the Lambert Glacier basin, East Antarctica, become drier.

scholarly journals Summertime evolution of snow specific surface area close to the surface on the Antarctic Plateau

2015 ◽  
Vol 9 (4) ◽  
pp. 4499-4538
Author(s):  
Q. Libois ◽  
G. Picard ◽  
L. Arnaud ◽  
M. Dumont ◽  
M. Lafaysse ◽  
...  
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Summer Precipitation ◽  
Strong Wind ◽  
Near Surface ◽  
Antarctic Plateau ◽  
Annual Variability ◽  
Wind Events ◽  
The Antarctic

Abstract. On the Antarctic Plateau, snow specific surface area (SSA) close to the surface shows complex variations at daily to seasonal scales which affect the surface albedo and in turn the surface energy budget of the ice sheet. While snow metamorphism, precipitation and strong wind events are known to drive SSA variations, usually in opposite ways, their relative contributions remain unclear. Here, a comprehensive set of SSA observations at Dome C is analysed with respect to meteorological conditions to assess the respective roles of these factors. The results show an average two-to-three-fold SSA decrease from October to February in the topmost 10 cm, in response to the increase of air temperature and absorption of solar radiation in the snowpack during spring and summer. Surface SSA is also characterised by significant daily to weekly variations, due to the deposition of small crystals with SSA up to 100 m2 kg−1 onto the surface during snowfall and blowing snow events. To complement these field observations, the detailed snowpack model Crocus is used to simulate SSA, with the intent to further investigate the previously found correlation between inter-annual variability of summer SSA decrease and summer precipitation amount. To this end, Crocus parameterizations have been adapted to Dome C conditions, and the model was forced by ERA-Interim reanalysis. It successfully matches the observations at daily to seasonal time scales, except for few cases when snowfalls are not captured by the reanalysis. On the contrary, the inter-annual variability of summer SSA decrease is poorly simulated when compared to 14 years of microwave satellite data sensititve to the near surface SSA. A simulation with disabled summer precipitation confirms the weak influence in the model of the precipitation on metamorphism, with only 6 % enhancement. However we found that disabling strong wind events in the model is sufficient to reconciliate the simulations with the observations. This suggests that Crocus reproduces well the contributions of metamorphism and precipitation on surface SSA, but that snow compaction by the wind might be overestimated in the model.

scholarly journals Atmospheric moisture supersaturation in the near-surface atmosphere at Dome C, antarctic plateau

2016 ◽  
Author(s):  
Christophe Genthon ◽  
Luc Piard ◽  
Etienne Vignon ◽  
Jean-Baptiste Madeleine ◽  
Mathieu Casado ◽  
...  
Keyword(s):  
Climate Models ◽  
Ice Cores ◽  
Cirrus Clouds ◽  
In Situ Observation ◽  
Atmospheric Moisture ◽  
Near Surface ◽  
Weather Forecasts ◽  
Antarctic Plateau ◽  
One Year ◽  
The Antarctic

Abstract. Supersaturations in the natural atmosphere are frequent at the top of the troposphere where cirrus clouds form, but are very infrequent near the surface where the air is generally warmer and laden with liquid and/or ice condensation nuclei. An exception is the surface of the high antarctic plateau. One year of atmospheric moisture measurement at the surface of Dome C on the East Antarctic plateau is presented and compared with results from 2 models implementing cold microphysics parametrizations: the European Center for Medium-range Weather Forecasts through its operational analyzes, and the Model Atmosphérique Régional. The measurements are obtained using commercial hygrometry sensors modified to allow air sampling without affecting the moisture content even in case of supersaturation. Supersaturations are very frequent in the observations and in the models, but the statistical distribution differs both between models and observations and between the 2 models, living much room for improvements in both models. Unadapted hygrometry sensors generally fail to report supersaturations, and most reports of atmospheric moisture on the antarctic plateau are thus likely biased low. This is unlikely to strongly affect estimations of surface sublimation because supersaturations are more frequent as temperature is lower, and moisture quantities and thus water fluxes are very small anyway. Ignoring supersaturation may be a more serious issue when considering water isotopes, a tracer of phase change and temperature, largely used to interpret snow and ice samples from the antarctic plateau and reconstruct past climates and environments from ice cores. Longer and more continuous in situ observation series to test parameterizations of cold microphysics, such as those used in the formation of cirrus clouds in climate models, can be obtained at surface levels than higher in the atmosphere.

scholarly journals Spatial and Temporal Variations of Snow Chemistry in Terre Adélie (East Antarctica)

1985 ◽  
Vol 7 ◽  
pp. 20-25 ◽  
Author(s):  
Michel Legrand ◽  
Robert J. Delmas
Keyword(s):  
Ion Chromatography ◽  
Temporal Variations ◽  
Sea Salt ◽  
East Antarctica ◽  
Snow Chemistry ◽  
Antarctic Plateau ◽  
Time Period ◽  
Terre Adélie ◽  
The Mean ◽  
The Antarctic

The chemistry of recently deposited snow sampled in 1982–83 along a 430 km coast-interior traverse in Terre Adelie, East Antarctica, is reported. In addition, three firn samples, covering the same time period (1959 to 1969) and collected on the traverse at D 55, D 80 and Dome C stations, respectively at 200, 430 and 1070 km from the sea, are also studied. Concentrations of major soluble impurities (H+, , Na+, K+, Cl−, and ) were determined by ion chromatography (except H+ which was titrated) on more than 200 samples. Conditions of sampling and analysis were carefully controlled in order to avoid contamination problems. A balanced ionic budget was generally obtained for each of the samples. For stations occupying an intermediary position between the coastal areas and the central Antarctic plateau, our results demonstrate that the two major impurities are H2SO4 and HNO3. HCl is also present, but at a lower level of concentration; the sea-salt contribution is dominant only at the most coastal sites (within 40 km) of the sea. The degree of neutralization of the snow acidity by NH3 is always very low as indicated by the values of content. The mean concentrations of H2SO4 along the traverse are relatively constant whereas an increase of the HNO3 concentrations is observed when going inland. It decreases, however, in most central areas. These results are discussed in relation to the glaciochemical data published for other locations on the Antarctic plateau, in particular the sulphate concentrations which depend strongly on explosive volcanic activity.

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