The calving front of the Pine Island Glacier, seen by a NASA aircraft in 2016. Image: NASA IceBridge.

An iceberg about five times the size of Manhattan has broken off the Pine Island Glacier in West Antarctica over the past 24 hours, an ominous sign of the continued retreat of this fast-flowing mass of ice. Like many other marine terminating glaciers in Antarctica, this glacier is retreating over time, and increasing the movement of ice into the sea.

Why it matters: While this iceberg itself is not record-breaking — it ranks as the sixth-largest iceberg to break off the Pine Island Glacier since 2001 — it illustrates the continued instability of marine-terminating glaciers in parts of the icebound continent.

The details: The iceberg had first appeared as a rift across Pine Island Glacier in September, before leading to the calving of about 300 square kilometers, or 116 square miles, of ice. The largest individual iceberg measures about 226 square kilometers in area, or 87 square miles.

Stef Lhermitte, a geoscientist at the Netherlands' Delft University of Technology who closely tracks Antarctic ice, tweeted that the glacier front, where the ice meets the sea, has now receded by about 5 kilometers, or close to a mile inland compared to recent decades.

  • Ice shelves, such as the one at the Pine Island Glacier, act like door stops to the land-based ice behind it. Once they diminish, due to a combination of warming from the ocean below and air temperatures above, it's more likely that inland ice will collapse into the sea, raising global sea levels.

Determining the amount of future ice loss from Antarctica is the biggest source of uncertainty in sea level rise projections, but recent studies have suggested that Antarctic ice melt is likely to be at the higher end of the scale.

  • Recent research published in Nature Climate Change, found that "ice losses from Antarctica have accelerated during the past 25 years," and that 40% of the continent's sea level rise contribution has occurred during just the past 5 years.
  • Antarctica lost 1,883 billion tons of ice between 2007 and 2017, which was significantly higher than scientists estimated in a seminal report published in 2013.

The bottom line: The new iceberg is significant for reflecting trends taking place around Antarctica, which many climate scientists find worrisome.

Go deeper: West Antarctic ice melt poses unique threat to U.S., Antarctica has lost nearly 3 trillion tons of ice since 1992

Go deeper

Updated 2 hours ago - Politics & Policy

Coronavirus dashboard

Illustration: Aïda Amer/Axios

  1. Global: Total confirmed cases as of 12 p.m. ET: 10,920,457 — Total deaths: 522,385 — Total recoveries — 5,789,032Map.
  2. U.S.: Total confirmed cases as of 12 p.m. ET: 2,753,754 — Total deaths: 128,871 — Total recoveries: 781,970 — Total tested: 33,462,181Map.
  3. Public health: The states where face coverings are mandatory Fauci says it has been a "very disturbing week" for the spread of the coronavirus in the U.S.
  4. Business: Top business leaders urge the White House to develop mandatory mask guidelines.
  5. Economy: The economy may recover just quickly enough to kill political interest in more stimulus.
  6. States: Florida reports more than 10,000 new coronavirus cases, and its most-infected county issues curfew.
3 hours ago - Sports

Washington Redskins to review team name amid public pressure

Photo: Patrick McDermott/Getty Images

The Washington Redskins have announced they will be conducting a review of the team's name after mounting pressure from the public and corporate sponsors.

Why it matters: This review is the first formal step the Redskins are taking since the debate surrounding the name first began. It comes after weeks of discussions between the team and the NFL, the team said.

Scoop: Instacart raises another $100 million

Illustration: Sarah Grillo/Axios Visuals

Grocery delivery company Instacart has raised $100 million in new funding, on top of the $225 million it announced last month, the company tells Axios. This brings its valuation to $13.8 billion.

Why it matters: This funding comes at what could be an inflection point for Instacart, as customers it acquired during coronavirus lockdowns decide whether they want to continue with the service or resume in-person grocery shopping.