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Landscape on the Greenland Ice Sheet near Kangerlussuaq. America. North America. Greenland. Denmark. Photo: Martin Zwick/REDA&CO/UIG via Getty Images.

Sea level rise isn't the only thing we have to worry about as the Greenland and Antarctic ice sheets melt. A new modeling study finds that runoff from these ice sheets could significantly alter crucial ocean currents in ways that disrupt the Gulf Stream and accelerate ice loss in West Antarctica.

Why it matters: The study, published in the journal Nature on Wednesday, shows the potentially far-reaching ramifications of ice melt.

The big picture: Scientists are racing to better understand and anticipate the pace, extent and impacts of melting glaciers, both in Greenland and Antarctica. Since the last report from the UN Intergovernmental Panel on Climate Change in 2014, sea level rise estimates have increased, but uncertainties remain high.

  • The new study, by a group of researchers from New Zealand, Canada, Germany and the U.K., is one of the first to pair a climate model with an ice sheet model — fed with the latest observational data on ice loss — to see how ice melt might alter the planet's climate.
  • It finds that the influences may be profound.

The threat: If the Greenland or Antarctic ice sheets melt quickly and significantly enough, they could pour enough cold, relatively light freshwater into adjacent areas of the ocean to disrupt global ocean circulation, the study finds.

  • In particular, the study adds to the growing concern in the scientific community about a slowdown in a current known as the Atlantic-Meridional Overturning Circulation, or AMOC.
  • This current is also referred to as a global conveyor belt or global thermohaline circulation, carrying heat and oxygen from the bottom of the world to the far north, and back again.
  • There are clear signs that part of this current is already slowing down, due to freshwater inputs from Greenland.

The new study says this could lessen the heat transported to Europe and may make weather more variable in the northeastern U.S., among many other areas. Worse yet, in the Antarctic, adding freshwater to the surface ocean would serve to reduce the amount of mixing between ocean layers, the study says.

  • This would trap salty and warm water well below a film of cool, freshwater on the surface.
  • Such warm, salty waters are melting marine-terminating glaciers in West Antarctica by eating away at their floating ice shelves and infiltrating the ice bed in areas where the bedrock is below sea level.

What they're not saying: The study assumes that the ocean is not playing a large role in melting Greenland's glaciers, which is at odds with observations, according to Eric Rignot, a professor of Earth system science at UC Irvine, who was not involved in the new study.

  • Rignot says Greenland will melt faster and more extensively than the study's models show.

What they're saying: Luke Trusel, a study coauthor and geology professor at Rowan University, told Axios that melting ice sheets will have effects far beyond sea level rise.

"Ice sheets aren't passive bodies of ice, they're dynamic, interactive components of the Earth system. They change in response to climate, and climate then responds to their change."
— Luke Trusel, Rowan University

"'Melting ice sheets don't just cause sea level rise. They also disrupt the climate system, by dumping a lot of cold freshwater into the ocean," says study coauthor Kaitlin Naughten of the British Antarctic Survey, in an email to Axios. "This affects deep ocean circulation, surface ocean currents, and weather patterns across the globe."

Go deeper:

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Scoop: Gina Haspel threatened to resign over plan to install Kash Patel as CIA deputy

CIA Director Gina Haspel. Photo: Win McNamee/Getty Images

CIA Director Gina Haspel threatened to resign in early December after President Trump cooked up a hasty plan to install loyalist Kash Patel, a former aide to Rep. Devin Nunes (R-Calif.), as her deputy, according to three senior administration officials with direct knowledge of the matter.

Why it matters: The revelation stunned national security officials and almost blew up the leadership of the world's most powerful spy agency. Only a series of coincidences — and last minute interventions from Vice President Mike Pence and White House counsel Pat Cipollone — stopped it.

Updated 7 hours ago - Politics & Policy

Coronavirus dashboard

Illustration: Sarah Grillo/Axios

  1. Health: Coronavirus deaths reach 4,000 per day as hospitals remain in crisis mode — CDC warns highly transmissible coronavirus variant could become dominant in U.S. in March.
  2. Politics: Biden says, "We will manage the hell out of" vaccine distribution — Biden taps ex-FDA chief to lead Operation Warp Speed amid rollout of COVID plan — Widow of GOP congressman-elect who died of COVID-19 will run to fill his seat.
  3. Vaccine: Battling Black mistrust of the vaccines"Pharmacy deserts" could become vaccine deserts — Instacart to give $25 to shoppers who get vaccine.
  4. Economy: Unemployment filings explode againFed chair: No interest rate hike coming any time soon —  Inflation rose more than expected in December.
  5. World: WHO team arrives in China to investigate pandemic origins.

John Weaver, Lincoln Project co-founder, acknowledges “inappropriate” messages

John Weaver aboard John McCain's campaign plane in February 2000. Photo: Robert Schmidt/AFP via Getty Images)

John Weaver, a veteran Republican operative who co-founded the Lincoln Project, declared in a statement to Axios on Friday that he sent “inappropriate,” sexually charged messages to multiple men.

  • “To the men I made uncomfortable through my messages that I viewed as consensual mutual conversations at the time: I am truly sorry. They were inappropriate and it was because of my failings that this discomfort was brought on you,” Weaver said.
  • “The truth is that I'm gay,” he added. “And that I have a wife and two kids who I love. My inability to reconcile those two truths has led to this agonizing place.”