LAWRENCE -- Last month a new projection of sea-level rise by the year 2050 spurred headlines showing more coastal cities around the world will be submerged than earlier models have predicted. Just how fast and how high sea levels rise globally will be determined by the melting of ice sheets in Greenland and Antarctica. However, the acceleration, retreat and thinning of glaciers where they meet ocean water are still understood poorly.
"Our model projections for how ice sheets change are probably underestimates," said primary investigator Leigh Stearns, KU associate professor of geology and researcher with the Center for the Remote Sensing of Ice Sheets (CReSIS). "There's a lot about the physics of glaciers that we don't understand. It doesn't mean that we can't model them closely, but we're missing things. So, our estimates for sea-level rise have pretty big uncertainty, and that's mostly due to the contribution from ice because we are not able to constrain those processes very well. In order to do that, we really need detailed investigations of glaciers to try to pin down these relationships better. I would say we don't even really know if the ocean is pushing most of the change of the ice sheet, or if it's the atmosphere -- and there are people in our community who would argue both ways, very strongly. That's pretty a fundamental question we haven't really solved yet."
Now, with a four-year, $5.8 million award from the Heising-Simons Foundation, researchers headquartered at the University of Kansas are studying these intricate processes by gathering handpicked experts in an array of specialties to scrutinize ice-loss on just one key ice-sheet -- Greenland's Helheim glacier -- in what they term a "megasite" research project.
"Studies like this where we have a strong interdisciplinary group looking at one specific location, I think is a good way to drive understanding forward," Stearns said. "Clearly we're not going to be able to put instruments in every fjord in Greenland. So, we came up with the idea of having one or two megasites where we're really throwing all our resources at one system to try to figure out what are the important measurements that we need and what don't we need."
Stearns, who previously has earned funding from the Heising-Simons Foundation, was able to conceive the research project and select collaborators. She said it's especially important, for instance, that glaciologists collaborate with atmospheric scientists.
"The atmosphere changes and ocean changes on timescales that we don't entirely understand," Stearns said. "So, we really need people who are experts at working with atmospheric data and running models. We need their viewpoint. They might say, 'Oh, you know this year the response to the glacier was different -- but maybe that's because it was a warm December or it rains a lot in October,' whatever that signal is. For me to try to do that would be very crude. We need people who understand the individual processes and how they might link to the glacier. If the atmosphere is warmer or wetter or drier, that will impact how the glacier is flowing seasonally because some of that water gets to the bottom of the glacier and makes it speed up, but we don't really know that correlation very well."
Because the Helheim Glacier is losing ice at a high rate and contributing to sea-level rise, Stearns said it merits a scientific full-court press to grasp its mechanisms. But beyond that, she hoped understanding the facets of ice loss at the terminus of Helheim could also shed light on dwindling glaciers elsewhere in Greenland and around the world.
"It's a complicated glacier -- and that has its advantages and its disadvantages," she said. "It's important because it's discharging a lot, and it's changing a lot. When we worry about glaciers changing and causing sea levels to rise, this is one of the big ones that contribute a large percentage to the oceans. So, how it behaves matters. In that sense, we don't want to go to a glacier that isn't changing or doing anything significant, because it might be too simple and we might miss something. It's possible that Helheim is so complicated that what we learn doesn't directly translate to other systems. But I think for most of what we're learning it compares very well."
Team members travel in groups to Greenland together, but different work will occur at different times of the year.
"It's hard to do work there unless you've been there before," Stearns said. "You kind of need that background information, so some of us are trying to overlap the logistics as much as we can. Some of the projects need to be there at certain times of year -- for instance, the CReSIS team needs to go before there's melt because the radar does better when there's no water on the surface. But the atmosphere people want to go later, and ocean people want to go later because of the of sea-ice conditions. We're in the throes of that now, figuring out logistics. But it's nice that we can share support where we can."
Stearns said the Heising-Simons foundation set aside additional funds to benefit indigenous communities in Greenland living close to the glacier.
"They want to have a focus on giving back to the Greenlandic community that's near Helheim, and they wanted to have something specifically devoted to helping them," she said. "We proposed to put more time-lapse cameras in the fjords they might hunt in or travel in. There are a lot of small villages on different islands. So, putting cameras on the sea ice so that they could get a better sense of what the sea-ice conditions are before they travel to hunt or see family members could help. I'm excited about that focus on giving back to the community."
For her part, Stearns will contribute to the project by studying where the Helheim Glacier calves into icebergs at the margin of ice and sea.
Her collaborators on the megasite project at Helheim glacier are Sridhar Anandakrishnan of Pennsylvania State University, who will investigate the mechanics of fracturing ice; Douglas Brinkerhoff of the University of Montana, who will synthesize and analyze data collected at the glacier; Mathieu Morlighem of the University of California at Irvine, who will develop numerical models of the ice sheet; Luca Centurioni of the Scripps Institute of Oceanography, who will oversee measurements at the ice terminus; Fiamma Straneo of the Scripps Institute of Oceanography, who will track variability of fjord properties; Emily Shroyer of Oregon State University, who will model the fjord; Sarah Das of Woods Hole Oceanographic Institute, who will research the atmospheric record; Marco Tedesco of the Lamont Doherty Earth Observatory, who will examine atmospheric drivers and surface hydrology and also manage data.
"I'm just really excited to kind of be part of this interdisciplinary team and really have the opportunity to focus on the breadth of the question," Stearns said. "We're often kind of pigeon-holed into only looking at one piece of it in our work. So, it's nice to be given the avenue to focus on the things that we think are important."