Exploring how glacial meltwater-driven iron, carbon & microbial contributions impact primary productivity & atmospheric CO2 drawdown in the Amundsen Sea
The Thwaites glacier, roughly about the size of Florida or Britain, contains enough water on its own to raise sea levels worldwide by more than half a meter. It contributes about 4% of annual global sea level rise and has been called the most important glacier in the world. Satellite studies show it is melting far faster than it did in the 1990s.
That is one reason why scientists from around the globe have embarked upon a NERC and NSF partnership, the International Thwaites Glacier Collaboration (ITGC):
Warm ocean water from the Amundsen Sea circulates under the ice, causing it to melt. Melting loosens the ice from the bedrock below, causing it to flow faster and eventually to retreat into the deeper and thicker ice areas where it is likely to speed up still more.
Starting in 2018, and over the next five years, teams of scientists will explore the ocean and marine sediments, measure currents flowing toward the deep ice, and examine the stretching, bending, and grinding of the glacier over the landscape below. The project will involve more than 60 scientists and students.
As part of an ITGC partnership, University of Georgia professor Patricia Yager is returning to Antarctica, leading a team to the glacier to study the impact of glacial melting on the ecosystem of the Amundsen Sea. While an array of projects associated with the expedition are focused on sea level rise and the physical processes related to the melting, Yager is co-chief scientist and lead P.I. on the project ARTEMIS, designed to better understand the impact of melting glaciers and ice shelves, on the coastal ocean’s biological productivity.
Yager’s previous work in the region related the melting to the coastal productivity, the ecosystem, and the carbon cycle immediately adjacent to the ice shelf. Her team's research showed that the glacier melting was responsible for releasing iron, a limiting nutrient for the phytoplankton, triggering a bloom of algae. The rich ecosystem productivity of the Amundsen Sea Polynya acts as a massive sink for carbon dioxide (CO2) from the atmosphere, cycling more CO2 per square meter by a factor of 10 compared to the rest of the Southern Ocean.
“So, it’s a very efficient and large carbon sink, in addition to being a really important ecosystem,” Yager said. “And we showed that that system is very dependent on the melting glacier.”
Her team is connecting the dots to understand how the melting glacier is feeding the bloom.
“The melting is triggering the upwelling of warmer salty water from deep down below the surface of the ocean,” Yager explained. “That’s where the compost pile is – all the fertilizer for the algae that is recycled – and there is a lot of carbon in that deep water as well that is broken down.”
The melting of the glacier is happening very deep, where this very salty, dense but warm – think refrigerator temperature versus the freezer – water at the bottom of the ocean is flowing underneath the glacier at an increasing rate. The glacier is very thick – 600-700 meters thick – and so this warm salty water from the bottom is now increasingly getting pushed against the glacier.
“Consequently, now in the very deep water we have warm salty water, and then you create meltwater, which is cold and fresh. Mixed together, the combination is buoyant – the salinity is now changed in such a way that that water now floats up to the surface. This upwelling is carrying nutrients but it’s also carrying CO2,” Yager said.
The ARTEMIS project led by Yager seeks to understand how that melt rate correlates with what’s happening in the polynya, from year to year. Ultimately, they will try to determine whether the future ecosystem will helpfully take up CO2 from the atmosphere, as it does today, or send CO2 out to the atmosphere, perhaps making climate change even worse.
Joining Yager on the expedition is a diverse team of scientists, from well-seasoned researchers to Ph.D. candidates.
Hilde Oliver is an Assistant Scientist at Woods Hole Oceanographic Institution on Cape Cod (WHOI). She has developed numerical models to study how melting of the Greenland and West Antarctic Ice Sheets can impact the biological productivity of high-latitude coastal seas
Giovanna Azarias Utsimi is a third-year Ph.D. student in marine sciences at UGA. A graduate from the Federal University of Sao Paulo with a bachelor's degree in Marine Science and Environmental Engineering, her current research is focused on biogeochemical processes that can affect organic matter composition in coastal environments.
Patricia Medeiros is an associate professor of marine sciences at UGA whose expertise relies on the use of specific organic compounds, i.e., molecular biomarkers, to investigate sources, transport, transformations, and fate of organic matter in the aquatic and atmospheric environments.
Sharon Stammerjohn is a Senior Research Associate at the Institute of Arctic and Alpine Research of the University of Colorado, Boulder. Her primary research focuses on polar oceanography and climate, specifically on atmosphere-ocean-ice interactions, including ocean, sea ice and ice shelf interactions.
Janelle Steffen is Ph.D. student in Chemical Oceanography from Texas A&M University whose research investigates the use of iron isotopes as tracers for various chemical oceanography processes with locations focusing on both hydrothermal vents and throughout the Southern Ocean.
Robert Sherell is a chemical and geological professor in the department of marine and coastal sciences at Rutgers University. The Sherell lab studies the biogeochemistry of trace metals in the modern ocean and uses this understanding to develop new geochemical paleo-records of past ocean conditions, with particular interest in metals that act as micro-nutrients for phytoplankton. He has active research programs exploring the mechanisms of natural iron fertilization of ocean productivity in two shelf regions off west Antarctica.
Lisa Herbert is a marine biogeochemist, currently an EOAS Fellow at Rutgers University, working with Robert Sherrell and Yair Rosenthal, interested in elemental cycling between the ocean and sediments.
The team departs from Punta Arenas, Chile in early January aboard the research vessel, the Nathaniel B. Palmer, for the two-week voyage across Drakes Passage to Antarctica and the glacier. The expedition will last for a planned 65 days.
“With this project, we saw an opportunity to piggyback on the work of this amazing suite of glaciologists and physical oceanographers using the latest high-tech instruments (including two different robots that will go beneath the ice to measure the melting) working to understand what’s determining how fast the melting is happening, where that meltwater is going and how that might be important,” Yager said.
“It’s the perfect chance to make our biogeochemical measurements, in collaboration with those other measurements,” she said. “We can take all that information that they have and add to it now this understanding that this physical process is having an impact on the ecosystem.
Follow the real time progress and experiences of the team via Twitter @ARTEMISonICE
and Instagram @artemisonice