climate change in the antarctic. turner et al, 2006. significant warming of the antarctic winter...
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Climate change in the Antarctic
• Turner et al, 2006. Significant warming of the Antarctic Winter Troposphere. Science, vol 311, pp 1914-1916.
Radiosonde records have been digitized and passed quality control (Scientific Committee of Antarctic Research).
Climate change in the Antarctic
Turner et al, 2006
Annual and seasonal T trends at 500-hPa level (1971-2003)
Turner et al, 2006
Mean vertical profile of T trends for the 9 stations
40-year European Center for Medium-Range Weather Forecasts reanalysis set (ERA-40)
• Agrees with trends of radiosonde data
• Larger warming trends except over Antarctic Peninsula
• Another discrepancy in West Antarctica
Turner et al, 2006
• Major source of uncertainty: radiation correction (applied due to radiative effects on T sensor) study in winter, correction is small
• Data collected by different programs and instrument types. Analyses make them confident of their results.
Turner et al, 2006
500 mbar T for 9 stations and their mean
Also analyzed model (GCM) outputs, among other things agreement, on average, of a maximum warming in mid troposphere.
• Turner et al, 2006. Significant warming of the Antarctic Winter Troposphere. Science, vol 311, pp 1914-1916.
• Velicogna and Wahr, 2006. Measurements of Time-Variable Gravity Show Mass Loss in Antarctica. Science, vol 311, pp. 1754-1756.
Gravity Recovery and Climate Experiment (GRACE) satellites – 2002-2005
Climate change in the Antarctic
• Problems with methodology – no vertical resolution. Gravity changes due to change in snow and ice on the surface, atmospheric mass or post-glacial rebound.
• Other sources of error: errors in GRACE gravity fields and contamination from other geophysical sources of gravity-field variability.
Estimate and correct errors and arrive to confidence intervals of ~70%
Velicogna and Wahr, 2006
Velicogna and Wahr, 2006
• Turner et al, 2006. Significant warming of the Antarctic Winter Troposphere. Science, vol 311, pp 1914-1916.
• Velicogna and Wahr, 2006. Measurements of Time-Variable Gravity Show Mass Loss in Antarctica. Science, vol 311, pp. 1754-1756.
• Thompson and Solomon, 2002. Interpretation of Recent Southern Hemisphere Climate Change. Science, vol. 296, pp 895-899.
Climate change in the Antarctic
Thompson and Solomon, 2002.
• 30 yrs. (1969-1998) monthly mean radiosonde data from 7 stations
• 32 yrs. (1969-2000) monthly surface Temperature
• 30 yrs. (1969-1998) ground-based total column ozone measurements
(Halley station)
• 22 yrs. (1979-2000) tropospheric geopotential height data from
NCEP/NCAR reanalysis
They discuss the trends in tropospheric circulation and relate their results to warming in the Antarctic Peninsula and Patagonia (west) and cooling of eastern Antarctica and the Antarctic Plateau (east).
Trends are due largely to ozone losses.
Thompson and Solomon (2002) find a trend in the tropospheric circulation (with high westerly flow encircling the polar cap)
Largest and most significant trends can be traced and tied to trends in the lower stratospheric polar vortex.
Thompson and Solomon, 2002.
• Find trends in geopotential height data, consistent with SAM (large-scale pattern of variability dominating the SH wk-wk mth-mth t.s.)
• Months of high-index polarity of SAM cold polar Ts, low geopotential height over polar cap and strong circumpolar flow along 60° S
• SAM is accompanied by thermally indirect vertical motions at polar latitudes, high-index polarity favors cooling over much of Antarctica.
• Except for Antarctic Peninsula anomalously strong westerlies decrease the incidence of cold form the south and leads to increased advection from the Southern Ocean.
Thompson and Solomon, 2002.
• Modeling studies that run with increasing GHG and/or stratospheric ozone losses have also simulated these trends found in the SAM, or at least the same sign.
Ozone losses and anthropogenic activities
Summary
• Different observations are used, such as radiosonde data, satellite images, surface temperature and total-column ozone measurements to support the idea that even though we cannot determine with certainty the climate dynamics in the Antarctic region, there is evidence that climate change is taking place and that it can be linked to anthropogenic activity.