McMurdo Dry Valleys LTER

Long-term Research Reveals Temperature Trends in Antarctic Lakes

One of the key questions concerning the future of all ecosystems on our planet is how they will respond to natural and anthropogenically induced climate change.

A) PAR at 10m for Nov and Dec (mol photons m-2d-1) B) Primary Productivity (mg Cm-2d-1) C) Nematode density (per kg dry soil)

The McMurdo Dry Valleys (MCM) represent the largest ice-free area in Antarctica and are among the coldest and driest terrestrial environments on the planet. They contain a number of ice-covered, closed-basin lakes. Lake level records collected primarily by New Zealand scientists indicated that the MCM region had been warming in the 1970s into the 1980s. Our meteorological data from Lake Hoare in Taylor Valley represent the longest continuous climate record on the Antarctic continent. Long-term studies at the MCM-LTER site have documented a cooling trend in this portion of Antarctica over the past decade. Seasonally averaged surface temperature has decreased by 0.56°C per decade over a 14-year period.

This environment has long been viewed as extremely sensitive to small changes in climate. As the climate has cooled, MCM-LTER scientists have documented an increase in ice thickness on the lakes, as well as a decrease in lake levels. In addition to these physical changes, we have observed an increase in lake salinity, a decrease in primary production, and dramatic changes in phytoplankton composition within the lakes over this time period. The increase in thickness and reduced underwater irradiance has led to a primary production decrease of 5% per year from 1989 to 2000. Declining populations of nematodes in the soils and changes in algal mat types in the streams have also been observed. Without continuous, long-term monitoring these changes in the ecosystem of the McMurdo Dry Valleys could not have been linked directly to the physical forcing.