Common thread at 2015 AGU Conference: Global warming and ‘The Big Melt’

Desdemona Despair

By Bob Henson 
18 December 2015

(Weather Underground) – The weather story of this month is the record warmth swaddling much of eastern North America and Europe. We’ll have much more to say about that next week, but keeping with the warm theme for today, I’ll share a couple of melt-related tidbits that drew my attention at this year’s Fall Meeting of the American Geophysical Union, which Jeff Masters and I attended this week.

This is the world’s largest gathering of Earth-related scientists, with more than 20,000 researchers, journalists, and others in attendance. Thousands of posters and talks cover the whole spectrum of Earth sciences–at any one moment, there can be 50 or more presentations going on. Various science journalists and WunderBlog commentors have done a great job of capturing the broad array of science presented this week.

You can browse the enormous number of abstracts at the meeting website. Many of the presentations were recorded and are now available through AGU On Demand (free registration is required). Here’s a full list of those recorded sessions. (Thanks for WU member spbloom for the tip.] If the drip-drip-drip of climate change news starts getting to you, there’s a handy remedy: Jeff’s AGU post from Wednesday, “The Top Ten Reasons to be Hopeful on Climate Change”.
Lots of red on the Arctic Report Card

NOAA introduced its 2015 Arctic Report Card with a press conference on Tuesday, viewable in archive form (as are all of the press conferences). The Arctic’s grades were not good. Our northern polar regions are failing–that is, failing to shield themselves from the relentless build-up of greenhouse gases. The polar year running from October 2014 to September 2015 was the warmest in more than a century of recordkeeping, with the region now 3°C (5.4°F) warmer than it was at the start of the 20th century.

The minimum summer extent of Arctic sea ice, which occurred on September 11, was not a record–it ranked fourth lowest in the satellite era (starting in 1979). However, the maximum winter extent did set a record low, and that occurred on February 25, two weeks ahead of average and the second earliest max in the satellite era.

One of the lesser-known but still profound changes to the Arctic is the decline in June snow cover, which is decreasing at around 18% per decade. Because the northern sun is at its strongest in June, this decline means that a good deal less sunlight is being reflected from polar regions, thus allowing more absorption of heat at the surface.

More than polar bears at risk

Polar bears are the poster creatures of climate change, which makes it easy to overlook how warming temperatures might affect other Arctic creatures. These impacts can be difficult to pin down, because there are complicated intersections between human-driven warming and other anthropogenic factors, such as variations in hunting rates over time and the build-up of oil and gas infrastructure.

An increase in rain-on-snow events over the Arctic is already having noteworthy impacts on reindeer, which forage for vegetation beneath snow cover during winter. A record number of reindeer (about 20% of a herd of 300,000) died in the winter of 2013-14 on the Yamal Peninsula of Western Siberia. A team led by Bruce Forbes (University of Lapland) described its post-event research in an AGU poster.

“More than a year later, participatory fieldwork with nomadic herders during spring-summer 2015 revealed that the ecological and socio-economic impacts from this extreme event will unfold for years to come,” the group reported. They’re now investigating whether the loss of sea ice in the Barents and Kara Sea is playing a role in the growing prevalence of rain-on-snow events. “There is an urgent need to understand whether and how ongoing Barents and Kara Sea ice retreat may affect the region’s ancient and unique social-ecological systems.”

The state of Arctic walrus is analyzed in detail in this year’s Arctic Report Card. Sea ice is an integral part of walrus life: adults hang out and mate along the edges of pack ice in the winter, and mothers bear their young on ice in the spring. As sea ice retreats further from the shore of Chukchi Sea in late summer, walruses have been making dramatic “haulouts” over land, where young walrus are especially vulnerable to being trampled in the rush. An estimated 35,000 walruses clambered onto the coast at Point Lay, Alaska, in September 2014, and thousands more did the same in 2015. [more]

Common Thread at 2015 AGU Conference: The Big Melt