Glacier melt adds ancient edibles to marine buffet

December 23, 2009

Glaciers along the Gulf of Alaska are enriching stream and near shore marine ecosystems from a surprising source - ancient carbon contained in glacial runoff, researchers from four universities and the U.S. Forest Service report in the December 24, 2009, issue of the journal Nature*.

In spring 2008, Eran Hood, associate professor of hydrology with the Environmental Science Program at the University of Alaska Southeast, set out to measure the nutrients that reach the gulf from five glaciated watersheds he can drive to from his Juneau office. "We don't currently have much information about how runoff from glaciers may be contributing to productivity in downstream marine ecosystems. This is a particularly critical question given the rate at which glaciers along the Gulf of Alaska are thinning and receding" said Hood.

Hood then asked former graduate school colleague Durelle Scott, now an assistant professor of biological systems engineering at Virginia Tech, to help analyze the organic matter and nutrient (nitrogen and phosphorus) loads being exported from the Juneau-area study watersheds. "Because there are few reports of nutrient yields from glacial watersheds, Eran and I decided to compare the result from a non-glacial watershed with those of a watershed partially covered by a glacier and a watershed fully covered by a glacier," said Scott.

Hood and Scott's initial findings, reported in the September 2008 issue of the journal Nature Geoscience (http://www.nature.com/ngeo/journal/v1/n9/abs/ngeo280.html), presented something of a mystery. As might be expected, there is more organic matter from a forested watershed than from a fully or partially glacier-covered watershed. With soil development, organic matter is transported from the landscape during runoff events. However, there was still a considerable amount of organic carbon exported from the glaciated landscape.

How can a glacier be a source of the organic carbon? His curiosity peaked, in spring 2009, Hood's Ph.D. student, Jason Fellman, collected samples from 11 watersheds along the Gulf of Alaska from Juneau to the Kenai Peninsula. The samples were analyzed to determine the age, source, and biodegradability of organic matter derived from glacier inputs.

"We found that the more glacier there is in the watershed, the more carbon is bioavailable. And the higher the percentage of glacier coverage, the older the organic material is - up to 4,000 years old," said Scott.

Hood and Scott hypothesize that forests that lived along the Gulf of Alaska between 2,500 to 7,000 years ago were covered by glaciers, and this organic matter is now coming out. "The organic matter in heavily glaciated watersheds is labile, like sugar. Microorganisms appear to be metabolizing ancient carbon and as the microorganisms die and decompose, biodegradable dissolved organic carbon is being flushed out with the glacier melt," said Scott.

How much? "Our findings suggest that runoff from glaciers may be a quantitatively important source of bioavailable organic carbon for coastal ecosystems in the Gulf of Alaska and, as a result, future changes in glacier extent may impact the food webs in this region that support some of the most productive fisheries in the United States," said Hood.
-end-
*The article, "Glaciers as a source of ancient, labile organic matter to the marine environment," was authored by Hood; Fellman, now at the Institute of Arctic Biology at the University of Alaska Fairbanks; Robert G.M. Spencer and Peter J. Hernes of the Department of Land, Air and Water Resources at the University of California Davis; Rick Edwards and David D'Amore of the Pacific Northwest Research Station of the U.S.D.A. Forest Service in Juneau, and Scott.

The research is supported by Scott and Hood's three-year grant from National Science Foundation to study the impact of Alaska's melting glaciers on the transport and fate of nutrients in coastal watersheds in the Gulf of Alaska.

Also as part of the NSF-funded research, this past summer, Scott and his Ph.D. student, Michael Nassry of Hopwood, Pa., along with biological systems engineering senior Andrew Jeffery of Fairfax, Va., who was doing a 10-week undergraduate research study with Hood, conducted the first hydrologic tracer experiment on a supraglacial stream -- a stream entirely on top of the glacier. The helicopter company Northstar provided complimentary transportation to the base camp on the Mendenhall Glacier, where the team injected a salt, reactive nitrogen, and phosphorus over a 150 meter range, then collected water samples over a five-hour period. "At the end of the experiment, the helicopters were no longer flying, which provided the opportunity to sleep on top of the glacier," said Scott. Samples from this experiment are still being analyzed, and initial findings will be presented at the annual meeting of the American Geophysical Union December 14-18 in San Francisco.

Learn more about Eran Hood's research at http://www.uas.alaska.edu/dir/ewhood.html

Learn more about Durelle Scott's research at https://filebox.vt.edu/users/dscott/web/

Virginia Tech

Related Glaciers Articles from Brightsurf:

Rock debris protects glaciers from climate change more than previously known
A new study which provides a global estimate of rock cover on the Earth's glaciers has revealed that the expanse of rock debris on glaciers, a factor that has been ignored in models of glacier melt and sea level rise, could be significant.

New 'law' to explain how glaciers flow over soft ground
Addressing a major source of uncertainty in glacier-flow models, researchers present a new slip law to describe glaciers sliding on soft, deformable material.

Melting glaciers will challenge some salmon populations and benefit others
A new Simon Fraser University-led study looking at the effects that glacier retreat will have on western North American Pacific salmon predicts that while some salmon populations may struggle, others may benefit.

How the ocean is gnawing away at glaciers
The Greenland Ice Sheet is melting faster today than it did only a few years ago.

Last remaining glaciers in the Pacific will soon melt away
The last remaining tropical glaciers between the Himalayas and the Andes will disappear in the next decade -- and possibly sooner -- due to climate change, a new study has found.

Drones help map Iceland's disappearing glaciers
Dr. Kieran Baxter from the University of Dundee has created composite images that compare views from 1980s aerial surveys to modern-day photos captured with the help of state-of-the-art technology.

Disappearing Peruvian glaciers
It is common knowledge that glaciers are melting in most areas across the globe.

New insight into glaciers regulating global silicon cycling
A new review of silicon cycling in glacial environments, led by scientists from the University of Bristol, highlights the potential importance of glaciers in exporting silicon to downstream ecosystems.

Tidewater glaciers: Melting underwater far faster than previously estimated?
A tidewater glacier in Alaska is melting underwater at rates upwards of two orders of magnitude greater than what is currently estimated, sonar surveys reveal.

Asia's glaciers provide buffer against drought
A new study to assess the contribution that Asia's high mountain glaciers make to relieving water stress in the region is published this week (May 29, 2019) in the journal Nature.

Read More: Glaciers News and Glaciers Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.