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Warming Trend | Antarctic Climate Change in the Last Fifty Years

Antarctic climate change is older than most would assume, and Antarctica did not always have the climatic features that it possesses now. Antarctica had been much warmer in its distant geological past, such that there are fossils to indicate that trees grew in Antarctica at various geological times. As expected, Antarctica was placed in different locations many millions of years ago and with the movement of tectonic plates, this played a significant part in influencing Antarctica’s climate in the distant past. However, Antarctica has remained an almost completely ice-covered continent for at least the last 6 million years. The much older geological evidence of a warmer Antarctic however, cannot be an exact guide.

SAGHAA IV 2017

Studies of Past Antarctic Climate Change

The ice core samples from Antarctica show records that extend back to a period of about 800,000 years ago. In this time span, land and sea distribution globally has remained roughly the same as in present times and studies of Antarctic ice are more informative about climatic variability under the present tectonic configurations than of any geological period in the distant past. Studies on these ice cores can thus provide a more accurate foretelling about the near future over Antarctic climate change conditions.

Ice cores are obtained by drilling into a glacier or an ice sheet to extract a section of ice that is cylindrical in shape. These long sections of ice represent snow deposits going back by many thousands of years. Snow that settles on the surface falls over previous layers of snow, and with the passage of time, these become compressed to form glacial ice. Each layer in the ice core, like in soil deposits visible in certain canyons at other parts of the Earth, represents snow that had fallen at a certain time in the past. Each layer in the ice core thus functions as a time capsule, with samples that can tell researchers about the atmospheric composition of the deposition of snow at the time, for example, which might be helpful in identifying the patterns of climate at the time

.Fig: An Extracted ice core
Source: NASA

Ice cores can greatly help in understanding Antarctic climate change in many ways. Studies by the British Antarctic Survey (2017) reveal that the mean annual surface air temperature in Antarctica has fluctuated by over 10oC over the extent of the time frame that Antarctic ice cores can represent, going back to many thousands of years. There is also correlation between the Antarctic and the North Pole over the pattern of glacial and interglacials occurring in the past, with correlation also in the cases of levels of carbon di oxide and methane in Antarctic ice cores corresponding to periods of global cooling and warming. Their most significant finding however is that the current concentrations of atmospheric greenhouse gases are higher than in any other period recorded in the extracted Antarctic ice cores.

In another study led by Matthew Amesbury of the University of Exeter (2013), studies of mosses and microbes in southern Antarctica reveal that unprecedented ecological changes have occurred over the last 50 years in the region chiefly due to warmer temperatures. The Antarctic Peninsula is among the most rapidly warming places on Earth, with an average of a 0.5oC rise in annual temperatures here each decade since the 1950s. The study was a bid to understand the changing ecology in the region.

A more recent study following up on the one published in 2013 was led by Dan Charman, a researcher at the University of Exeter (2017). In this study, the dramatic effect on moss banks in Antarctica due to increases in temperature was highlighted, with a rapid increase in growth rates and also in microbial activity. Charman came to the conclusion that if this warming were to continue, Antarctica might have much more vegetation in the future.

Records of Antarctic Climate Change in the Last 50 Years

A published study on Antarctic climate change during the last 50 years based on a data set from the Reference Antarctic Data for Environmental Research (READER) project. The data set included data on near-surface temperature, mean sea-level pressure and wind speed in 19 stations in Antarctica over 50 years. Out of these, 11 stations reported warming trends and 7 stations reported cooling trends, with 1 station having too little data to be counted. The larger trend regarding Antarctic climate change over the last 50 years has been one of a major warming trend. The data indicates a greater warming trend in the period between the years 1961 and 1990 as compared to the period between 1971 and 2000.

Studies on Antarctic climate change and warming usually tend to focus on warming in the Antarctic Peninsula, which is among the most rapidly warming places on Earth, as mentioned before. This is coupled with many of Antarctica’s ice shelves disintegrating, and sites at low elevations by the Antarctic Peninsula such as the Bellingshausen Sea at the western coast of the Antarctic Peninsula which has witnessed great increases in temperature over the last 50 years. In fact, since the 1950s, the annual mean surface temperature at Vernadsky (formerly Faraday) station near the tip of the Antarctic Peninsula has witnessed an increase of about 2.5oC. In fact in Vernadsky station in the period between 1951 and 2000 has witnessed an increase in annual temperature by 0.56oC per decade.

In terms of mean sea-level pressure, all the stations in the study except for Orcadas (which has no records) recorded decreases in pressure, which was most prominent in Molodezhnaya and Mirny. The mean sea-level pressure over the Antarctic Peninsula was significantly lower than in other areas in the Antarctic, which could be attributed to differential heating as a constituent cause. Long term records for wind speed however, could only be collected for 11 coastal stations, out of which 8 have recorded wind speed increases in the last 50 years. The western part of the Antarctic Peninsula records the most consistent wind speed increases. Many studies serves to confirm the theory that warming has increased over the western Antarctica with the Antarctic Peninsula being particularly affected.

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