Old Ice

Chris Mooney, WaPo:

Over the past three decades of global warming, the oldest and thickest ice in the Arctic has declined by a stunning 95 percent, according the National Oceanic and Atmospheric Administration’s annual Arctic Report Card.

The finding suggests that the sea at the top of the world has already morphed into a new and very different state, with major implications not only for creatures such as walruses and polar bears, but in the long term, perhaps, for the pace of global warming itself.

The oldest ice can be thought of as a kind of glue that holds the Arctic together and, through its relative permanence, helps keep the Arctic cold even in long summers.

“The younger the ice, the thinner the ice, the easier it is to go away,” said Don Perovich, a scientist at Dartmouth who coordinated the sea ice section of the yearly report.

- and -

The new findings about the decreasing age of ice in the Arctic point to a less noticed aspect of the dramatic changes occurring there. When it comes to the icy cap atop the Arctic ocean, we tend to talk most often about its surface area — how much total ocean is covered by ice, rather than by open water. That’s easily visible — it can be glimpsed directly by satellite — and the area is, indeed, in clear decline.

But the loss of old and thick ice, and the simultaneous decline in the total ice volume, is even larger — and arguably a much bigger deal. Young and thin ice can regrow relatively quickly once the dark and cold winter sets in. But it may not add much stability or permanence to the Arctic sea ice system if it just melts out again the next summer.

Remember - it's the volume, not the area:

- and - keeping in mind the tendency of "conservatives" to cherry-pick the data, watch out for the assertion, "everything's just peachy because the ice is making a comeback" - along the same lines of their famous bullshit about how "AGW has paused, and the planet is actually cooling now".

In fairness, the ice volume has rebounded somewhat since 2012. And PIOMAS is only a model, cautioned the University of Washington’s Axel Schweiger, who runs the analysis. (The model draws upon direct measurements of ice thickness taken from submarines, satellites, and other sources.) Still, Schweiger agreed that when you think about the total volume of the ice, rather than its mere surface extent, you realize that far more has been lost.

“We’ve lost about half of the extent, we’ve lost half of the thickness, and if you multiply these two things, we’ve lost 75 percent of the September sea ice,” he said

Scientists get it wrong sometimes. I'll still take their word for things over the deniers because science is self-correcting - deniers will always just deny because that's what they believe, as opposed to people who can be convinced due to evidentiary knowledge.