科学家:气候变化导致极地冰川融化

Michael Gooseff follows water to the end of the earth. The Pennsylvania State University hydrologist works in remote regions of the Arctic and Antarctic, where ice and frozen ground are thawing. He expects polar warming and melting to continue at an accelerating pace if no significant reductions are made in climate-changing greenhouse-gas emissions.

At the annual convention of the Ecological Society of America in Austin, Texas this week he posed this question: “How are those polar systems responding to climate change?”  

The answer is based on his on-going research into how water crosses landscapes and what happens to it above and below ground.

“In the northern regions, of course, we have sea ice, but a smaller surface area than in the Antarctic where we have very large ice sheets. And that actually plays into the differences in climate change responses that we’re seeing at both of those places.”

According to Gooseff, the two regions also differ widely geologically and ecologically. He says the Antarctic McMurdo Dry Valleys station where he’s based “appears like a polar desert system with open exposed soils, with no vascular plants at the surface and with glaciers coming down from the mountains, whereas in northern Alaska, we have a lot of plants. The tundra is actually dense with vegetation and very green.”

Michael Gooseff

Gooseff is documenting change over time, by observing patterns in polar rivers, streams and lakes. He recalls a 2003 visit to Alaska’s North Slope, when his team charted the course of an unusual muddy stream.

“We follow this up and finally we found a big gash in the hill slope essentially, and all of this mud pouring out from underneath it.”

Here’s what had happened: A massive ice wedge under the surface had melted, thawing the permafrost and causing the soil above it to collapse. That created a deep gully in the hillside.

A study of historic aerial photos of the area revealed that this dramatic change, as well as similar warming-induced changes to 25 other landscape features, had occurred over just two decades.

Gooseff explains that as water moves through these altered formations, it picks up sediment and nutrients normally locked up in the permafrost. As that flows into rivers, it could affect fisheries and coastal oceans.

Michael Gooseff

Gooseff says the melting permafrost sets up another dangerous climate scenario.  “As we warm, we release more carbon, that carbon goes into the atmosphere, contributes to more warming, contributes to more permafrost degradation and the cycle sort of continues. In fact, permafrost itself is expected to hold about twice as much carbon as we currently have in the atmosphere.”

At the opposite end of the earth, near the McMurdo Dry Valleys station, Gooseff studies snow patches. Not much snow falls in Antarctica, but what little there is collects in cool shady spots, behind rocks and hills. These patches insulate the soil and may provide small amounts of moisture for microbes below.  

Gooseff says the melt from this frozen precipitation, as well as from older snowpack and glacier ice, is happening faster and is more widespread than a decade ago. The remote sensing devices his research team has deployed are helping to track how that water moves across the land.

“We expect that there are going to be patterns in both time and space that will be somewhat predictable.”

Gooseff hopes his research of climate change at the poles underscores the regions’ interconnectedness with a global climate system that affects everyone on the planet.