Results from a 20-year study reveal dramatic ecological changes to lakes in Antarctica caused by a 1 C temperature increase.
The findings, reported this week in Science, are yet more evidence of extreme changes in the Antarctic Peninsula region. This area has experienced some of the most rapid warming of anywhere on Earth in the past 50 years (2.5 C). The study lakes, on Signy Island, lie some 700 km north-east of the Antarctic Peninsula.
Scientists from the Cambridge-based British Antarctic Survey (BAS) are attempting to understand complex changes in the Antarctic and investigate the implications for global change.
The new results show that summer air temperatures increased by about 1 C during the study period. Each year Signy's lakes freeze and thaw. Between 1981 and 1995 the number of ice-free days increased by about a month. These conditions have caused lake water temperatures to rise by 0.2-1.3 C, whilst local sea temperatures remained the same.
An increase in the amount of solar energy absorbed and the introduction of nutrients transported by glacier melt-water flowing over exposed ground has altered the lakes' ecology. A ten-fold increase in the amount of phosphate has acted as a natural fertilizer, enabling algae to flourish.
Dr. Wendy Quayle, lead author of the research, says, "The value of long-term studies such as these -- there are no other records like this for Antarctica -- is our ability to observe the effects of an increase in temperature of just 1 C. We've seen how this can boost life in these lakes -- for example, there is now three times the amount of chlorophyll from algae in the lake than there was 20 years ago."
Professor Lloyd Peck of BAS says, "Because the Signy Island lakes used in this study have not been contaminated by human or animal waste they are very different from lakes in most parts of the world. The pristine nature of Antarctic lakes give us a unique natural laboratory -- where we can identify changes that are undetectable in contaminated lakes."
BAS Meteorologist John Turner says, "In recent decades we've seen a complex picture of temperature change over the whole Antarctic continent. Whilst the Antarctic Peninsula region has seen one of the largest temperature increases on Earth over the last 50 years, the South Pole has experienced a small cooling. However, what we can say with certainty is that Antarctica is extremely sensitive to environmental change."
British Antarctic Survey
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