Mixing it up
LARISSA encourages cross fertilization between disciplines
Posted September 18, 2009
So what do ice cores have to do with free-floating algal blooms? What is the link between seafloor sediments and hard-charging glaciers?
The LARISSA program is taking a “systems” approach to the study of the Larsen Embayment, where the collapse of a 10,000-year-old ice shelf will allow access to a quickly evolving ecosystem. The scientists who will work aboard the RVIB Nathaniel B. Palmer represent disciplines as diverse as glaciology, biology, oceanography and sedimentology.
How will the findings from one branch inform the work of the others? It’s a question the scientists themselves are still figuring out.
“By studying the system all at once we’re going to find ways in which one research discipline feeds into another one,” said Ted Scambos , lead scientist at the National Snow and Ice Data Center (NSIDC) in Boulder, Colo.
For example, Scambos said the Crane Glacier fjord intrigues both the glaciologists and the marine geologist, Eugene Domack — the chief scientist for the two-month science cruise who specializes in sedimentology and paleoclimate — because the retreat of the glacier allows them to map the entire fjord by sonar. The fjord shows a series of deep pockets, which both scientists think represent a chain of lakes that formerly lay under the ice.
“Eugene sees a potential climate record in the sediment layers left by the lakes — and what I see is evidence that some of the recent speed-up of the glacier may be caused by yet another lake, still under the ice,” Scambos explained.
As this lake drains, the glacier surface lowers, and becomes steeper, causing it to speed up. “So there’s a link between what the marine geology is doing and what the glaciology program hopes to measure right there,” Scambos said.
Another connection involves the eventual analysis of an ice core that a team from The Ohio State University will drill into a 2,000-meter-high ice ridge on the Antarctic Peninsula. In addition to a detailed temperature record that the scientists will glean by measuring the relative abundances of the different isotopes of oxygen and hydrogen preserved in the ice, various chemicals in the ice will have other stories to tell.
Biologist Maria Vernet said the ice core team will analyze a derivative of the sulfurous compounds produced by phytoplankton in the water, linking glaciology and biology.
Photo Credit: Wendy Kozlowski
Maria Vernet runs samples in the lab aboard the ARSV Laurence M. Gould.
“That is going to give us a long-term idea of phytoplankton production in the Larsen area,” said Vernet, with the Scripps Institution of Oceanography at UC San Diego . “As phytoplankton only lives a few days to a few weeks, chemicals accumulated in the ice can help illustrate productive events in the past.”
“We will then relate productivity in the past with ice shelf extent, and reconstruct the past based on what we learn on the cruise of present-day production and ice shelf dynamics,” Vernet said.
Ellen Mosley-Thompson , the lead investigator of the Ohio State team, said she expects to develop a lot of synergy between the ice-core record and discoveries by other members of the team.
“I think the information we will provide will be informative for the other team members,” she said. “I’m also confident that once we’ve reconstructed the various chemical and physical profiles, there will be things that we’ll see in our record that we won’t be able to interpret independently. We will need the information, for example, coming from the sediment cores.”
The cores from the seafloor mud provide their own paleoclimate record based on the types of sediments and rocks found. In addition, the sediments can provide clues as to what mechanisms might have been at work before the Larsen B Ice Shelf collapsed. What role might a subglacial lake have played in the instability of the ice shelf? How did the grounding line where the ice attached to bedrock erode?
“These are all really important questions in terms of interpreting other Antarctic sequences that have been drilled,” noted Domack, referring to other sediment-drilling programs like the Cape Roberts Project and ANDRILL on the other side of the continent.
Noted Scambos, “It’s a great area to invest all of this effort into, and we’re really making maximum use of everything the Palmer can do,” he said. “We’re really living up to the interdisciplinary concept that [the National Science Foundation ] has been talking about for a long time.”
The LARISSA project is one of two large, integrated IPY projects — the other is studying the Pine Island Glacier region — that are funded by NSF’s Antarctic Integrated System Science (AISS) program , which came online in 2007, and is intended to be the home for integrated projects, both large and small.
NSF-funded research in this story: Eugene Domack, Hamilton College, Award No. 0732467 ; Ted Scambos, University of Colorado at Boulder, Award No. 0732921 ; Ellen Mosley-Thompson and Lonnie Thompson, Ohio State University, Award No. 0732655 ; Maria Vernet, University of California-San Diego Scripps Institution of Oceanography, Award No. 0732983 .