Antarctic terrestrial ecosystems abide: Changes in soils, lakes and streams of the McMurdo Dry Valleys as the cooling trend ends

Background/Question/Methods

Ecosystems are significantly influenced by their physiography, geographic setting, and climate. The McMurdo Dry Valleys (MDV) experienced a decadal cooling trend in mean annual (-0.7°C/decade) and austral summer (-1.2°C/decade) air temperatures, and increasing solar radiation (+8.1 W/m²/decade) from 1986 to 1999.  The MDV ecosystem responded with decreases in soil invertebrate populations, glacial meltwater generation, chlorophyll-a content in stream algal mats and lake water columns, lake levels, and lake primary productivity, and increases in lake ice-cover thickness.  In the 2001-02 austral summer, the highest flow season since 1993 occurred as a consequence of several weeks of warm, cloud-free weather.  In the decade since, mean summer air temperatures have stabilized at cool temperatures (no trend 2003-2011, mean of -4.2°C, variance of 0.15°C). We now seek to determine how the MDV ecosystem responds since the end of the cooling trend.

Results/Conclusions

Coincident with the summer air temperature stability, responses observed to be coincident with the cooling trend have ceased (no patterns in soil invertebrate populations, stream algal mat chl-a), reversed (stream algal mat biomass, lake level rise, lake ice thinning, lake primary production), and some have become more pulsed (meltwater production). These changes in ecosystem properties since the 2001-02 summer further demonstrate the primary control of climate on this ecosystem, and also indicate the differential responses to climate for communities in each landscape unit.