Saturday, July 20, 2013

Peak Global Sea Ice is Lowest in the Satellite Era

Update 7/21: This post is incorrect. Global sea ice extent has two peaks in a year, one around June/July and a higher one in November. My figure confused the two, and actually this June's local maximum is higher than in most recent years. Here's the plot from Cryosphere Today.

This year's first peak in SIE was 14th lowest out of 35 years. (2011 is lowest, and 2012 next lowest.) For the annual maximum that occurs late in the year, 2012 was the lowest so far, with 2011 second-lowest.

Global sea ice extent has maxed out for the year at 25.30 million square kilometers (on June 26th), it's lowest value ever in the satellite era:


David Messineo said...

Anyone who still questions global warming can just go to Portage Glacier near Anchorage and see how this tidewater glacier has noticeably receded since the 1990s. We saw it firsthand this past week.

Steve said...

Ha! I was just watching a video of Roy Spencer's testimony to the Senate from earlier this week, in which (towards the end), he claimed there were some "half truths"being peddled by other witnesses - like the one who talked about decreasing Arctic Ice, but didn't mention increasing Antarctic Ice.

He has a hide. The video can be seen on Youtube here:

Robert Grumbine said...

David (Appel):
Your figures are for sea ice extent, not area. Your point holds either way. Sea ice is seldom a solid pack. There's open water even in the high Arctic in winter. Area won't count that water, but extent will. (nit: its, not it's in your comment)

David (Messineo):
you want more than 20 years for deciding what glaciers are doing in a climate sense. Fortunately, we have more than that, and your conclusion holds. See for a collection of glacier photos taken from the same vantage to over 100 years apart.

Arno Arrak said...

When you combine Arctic and Antarctic sea ice volumes you are mixing apples and oranges. There is nothing much interesting happening in the Antarctic except that the ice is being undercut in places by up-welling warm water. In the past this has led to periodic collapses of the ice sheet. According to the sedimentary record a large amount of melt water cascaded into the Ross Sea 18,000 years ago, again 10,500 years ago, again 5,500 years ago and then again 1,500 years ago. This tells us that if warm water keeps undermining the ice, as it still is, we can look forward to another such periodic collapse in a somewhat unpredictable future. The ice sheet facing the Amundsen Sea in particular is being undermined because shore winds push the cold surface water away and warmer water from below replaces it. In the Arctic the situation is entirely different. The Arctic today is the only part of the world that is still warming. That is possible only because Arctic warming is not greenhouse warming. It began at the turn of the twentieth century after 2,000 years of slow cooling, paused for 30 years in mid-century, then resumed, and is still going strong. There was no increase of atmospheric carbon dioxide when the warming started and this is what rules out the greenhouse warming as its cause. That is because the infrared absorbency of carbon dioxide is a property of the gas and cannot be changed. You must increase the number of absorbing molecules to start a warming. The start of warming was caused by a relatively rapid reorganization of North Atlantic current system that began carrying warm Gulf Stream water into the Arctic ocean. The pause in mid-century would then be explained by a temporary return of the former flow pattern of currents. Direct measurement of ocean temperature by research vessel in 2010 showed that water temperature reaching the Arctic now exceeds anything within the last 2,000 years. In addition to North Atlantic currents a lesser amount of warm water enters through the Bering Strait. It is usually enough to clear the Chuckchi Sea of ice in the summer. But in 2007 pole-ward winds brought so much warm water through that it melted a large patch of open water to its north. The Russian side was unaffected. And what about the future? The warming continues, but nature is fickle and what has happened before can happen again. What if the warming pause of mid-twentieth century should repeat itself? Someone ought to study this to avoid being blindsided by nature. Arno Arrak