How will Antarctica respond to global warming?

Long-term studies show potential impacts of climate change

Antarctic biodiversity is at risk from climate change. Photo by Bob Berwyn.
Antarctic ecosystems are at risk from climate change. @bberwyn photo.

Staff Report

A new set of scientific reports highlights the value of long-term observations in relatively undisturbed ecosystems and also offers a preview of how global warming may change Antarctica in coming decades.

The research shows that a period of unusual warmth in 2001 and 2002, caused by a confluence two natural climate cycles,  accelerated the microbial food chain and shook up the distribution of penguin populations and thinned glaciers according to October issue of the journal BioScience .

The research came out of two long-term ecological research stations, including Palmer Station, on the West Antarctic Peninsula, where scientists study how “changing sea ice extent influences marine ecology and the multilayered food webs of the coastal, nearshore, and continental slope ecosystems.” Other studies were done at the  McMurdo Dry Valleys LTER, in an ice-free polar desert where glacial meltwater plays a huge role in ecosystems.

Both sites are supported by the National Science Foundation, which manages the U.S. Antarctic Program, the nation’s research program on the southernmost continent.

“These two vastly different polar ecosystems offer insights into how diverse ecosystems around the world will respond to climate change,” said Hugh Ducklow, the Columbia University ecologist who leads the Palmer LTER. “With long-term studies already in place, we were able to observe the effects on so many different levels.”

On the West Antarctic Peninsula, the climate shift thickened sea ice along the shore, while increased melting at the edge flushed a surge of fresh water and ice algae directly into the upper mixed layer of the ocean. These nutrient inputs supported a large spring algal bloom and a population boom of Antarctic krill, a major food source for penguins, whales, seals, fish and flighted seabirds.

The same atmospheric patterns brought high snowfall amounts and earlier spring snowmelt to the coastal region along the peninsula. The runoff flooded the nests of early-hatching Adélie penguins to the benefit of later-nesting gentoo and chinstrap species.

In the Dry Valleys, a warm, downsloping foehn wind (similar to the Chinook) melted mountain glaciers and delivered water to a normally parched landscape. The runoff scoured streambeds, raised lake levels, and revealed windblown dust deposits hidden in the glaciers. The characteristic thick layer of lake ice (typically 4-6 meters) also thinned rapidly, allowing more sunlight than usual to reach the upper layers of the plankton community that thrives in lake water under the ice.

At the same time, inputs of dissolved organic carbon from newly active streams fed increased bacterial productivity deeper in the lakes. Early results from genomic studies suggest that one season of change may drive long-term changes in the structure of the lakes’ microbial communities.

At Palmer LTER, the physical impacts of the 2001-2002 climate anomaly were transient. At McMurdo, that single season of warming marked the start of nearly a decade of rising lake levels with an initial pulse of increased turbidity.

The changes show how ice buffers ecosystems from impacts. The  long-term ecological studies  enable scientists to capture insights from today’s brief climate excursions to understand how ecosystems may respond when the unusual becomes the typical.

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