Sign up for our daily briefing

Make your busy days simpler with Axios AM/PM. Catch up on what's new and why it matters in just 5 minutes.

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Catch up on coronavirus stories and special reports, curated by Mike Allen everyday

Catch up on coronavirus stories and special reports, curated by Mike Allen everyday

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Denver news in your inbox

Catch up on the most important stories affecting your hometown with Axios Denver

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Des Moines news in your inbox

Catch up on the most important stories affecting your hometown with Axios Des Moines

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Minneapolis-St. Paul news in your inbox

Catch up on the most important stories affecting your hometown with Axios Twin Cities

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Tampa Bay news in your inbox

Catch up on the most important stories affecting your hometown with Axios Tampa Bay

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Charlotte news in your inbox

Catch up on the most important stories affecting your hometown with Axios Charlotte

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Iceberg in the Southern Ocean, where deep ocean waters are seeing rising temperatures and a trend toward lower salinity values. Photo: Freedive Antarctica/Barcroft Media via Getty Images

The Southern Ocean is the planet's main heat and greenhouse gas sink, and without it, global warming would be a lot worse. It's also one of the least-observed and understood parts of the global ocean, due largely to its remoteness and competing influences there, from Antarctic sea ice to changing weather patterns and the slow healing of the stratospheric ozone layer.

The context: We've long known that on the ocean surface, parts of the Southern Ocean have been cooling over time, while deeper waters have been warming and freshening. But why these disparate trends have occurred has eluded scientists.

In a new study, published this week in the journal Nature Geoscience, scientists compiled the most comprehensive set of Southern Ocean observations available from 1950-2014. The study compares observations collected by ships and floats with model results.

They then used a "detection and attribution" approach using computer modeling combined with statistical techniques and observations to determine what causes of climate change best align with observed changes.

What they found: A combination of increasing amounts of greenhouse gases in the atmosphere and the gradual healing of the human-caused ozone hole over Antarctica are the main two drivers of change in a large part of the Southern Ocean, with greenhouse gases playing the dominant role.

  • This suggests that as we emit more greenhouse gases, deep ocean warming and freshening will continue, potentially altering regional or even global ocean circulation.
  • The Southern Ocean is the region where deep water interacts with the atmosphere, acting as "Kind of a gateway between the atmosphere and the ocean" study lead author Neil Swart of the Canadian Center for Climate Modeling and Analysis, told Axios.

Study co-author Sarah Gille, a scientist at the Scripps Institution of Oceanography, told Axios that it's critical that scientists better understand changes underway in the Southern Ocean, otherwise we won't be able to project the future climate with any accuracy.

"The Southern Ocean is the major connector between the Atlantic, Indian, and Pacific Oceans. The current system of the Southern Ocean, the Antarctic Circumpolar Current, carries more water than any other current on the planet," Gille told Axios.

"We want to understand this system, because we'd like to know how much heat and carbon dioxide it will continue to absorb, and what might make it stop taking up heat and carbon dioxide."
— Sarah Gille, Scripps Institution of Oceanography

In an accompanying news & views piece, Nathaniel Bindoff, who was not involved in the study, says it's the first to apply a rigorous approach to estimate the relative importance of each factor causing Southern Ocean changes.

Go deeper

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 8 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.”