Arctic Sea Ice Minimum for 2019

The ice is melting everywhere.

One of the most dramatic melts is the North polar icecap, which is shrinking rapidly.  The US National Snow and Ice Data Center reports this fall on the “minimum” for 2019, based on measurements from several satellites [1].  On September 17, the area covered by ice was 4.15 million square kilometers, which is the second smallestarea  ever recorded (these records go back to 1979).

The NSIDC reminds us that there still could be a late season heat wave or storm that pushes the ice back even farther.  The lowest recorded minimum in 2012 was partly due to a powerful cyclone that smashed into the ice [2].

Changing winds or late-season melt could still reduce the Arctic ice extent, as happened in 2005 and 2010.  (from [1])

It seems clear that the ice is disappearing at the North pole, as it is everywhere.

These particular data are a bit tricky to define for a number of reasons.  For one thing, “sea ice cover” is a bit, well, slushy.  There can be a lot of ice in the water that is still mostly water, and a lot of chunks with water in between, and also ice under the surface.  The NSIDC has heuristics for estimating these, and for defining areas “covered” with sea ice, so these annual estimates should at least be comparable to each other.

In addition to uncertainties in the data, there is no data at all before 1979, a mere 40 years ago.  So, we can’t really say much about long term trends in the past.  And while this year is the second lowest on record, over the last dozen years the data are basically going up and down in a small range.  We are in a relatively low ice period, but things aren’t changing fast.

Still, I’d bet the ice will continue to shrink, just as all the models predict.  This will have, and probably already is having, a positive feedback effect on ocean temperatures.  Exposed sea water is darker and absorbs sunlight faster than ice, increasing the warming in the summer, and generating warmer water that contributes to the overall warming of the oceans.

One thing that the melting ice cap does not do is increase sea levels, at least in any direct sense.  Going from ice to liquid reduces the volume of the water.

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1. National Snow and Ice Data Center, Arctic sea ice reaches second lowest minimum in satellite record, in Arctic Sea Ice & Anaysis. 2019. https://nsidc.org/arcticseaicenews/2019/09/arctic-sea-ice-reaches-second-lowest-minimum-in-satellite-record/
2. Maria-José Viñas, 2019 Arctic Sea Ice Minimum Is Second Lowest, in NASA Earth Observatory. 2019. https://earthobservatory.nasa.gov/images/145641/2019-arctic-sea-ice-minimum-is-second-lowest

East Antarctica is Melting, Too

It’s December, so it’s time for the AGU! (The American Geophysical Union Fall Meeting )  That means lots of splashy research results.

One of the reports from NASA indicates that the East Antarctic glaciers are “waking up” [2].

This sinding is important because we know that West Antarctic glaciers are moving and generally look to be thinning.  But there had been little indication of such changes in East Antarctica, as well.  Uh, oh.

The new study using satellite and other data shows that quite a few of the EA glaciers have accelerated in the past few years.  This is similar to the trends from other parts of Antarctica, so it can’t be too surprising.  And it also means that pretty much the whole continent is melting.

This map shows the flow of the Antarctic ice sheet as measured from the tracking of subtle surface features across millions of Landsat repeat image pairs. The “donut hole” marks the maximum latitude visible by the Landsat satellites. The data used for this map is an early version of the NASA MEaSUREs ITS_LIVE project and was produced by Alex Gardner, NASA-JPL. Credit: NASA Earth Observatory/Joshua Stevens (from [2])

With the Northern ice rapidly shrinking, and mountain glaciers receding everywhere, Antarctica round out the picture of a rapidly melting cryosphere.  In a century, the concept of a “cryosphere” of permanent ice will be a nostalgic memory.  Not that there will be very many human’s around: “There is enough ice in the drainage basins in this sector of Antarctica to raise the height of the global oceans by 28m.” [1]   Glub.

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1. Jonathan Amos, East Antarctica’s glaciers are stirring, in BBC News – Science & Environment. 2018. https://www.bbc.com/news/science-environment-46517396
2. Maria-José Viñas, More Glaciers in East Antarctica Are Waking Up, in NASA’s Earth Science News. 2018. https://www.nasa.gov/feature/goddard/2018/more-glaciers-in-antarctica-are-waking-up

Arctic Ice Minimum For 2018

The ice is melting everywhere.

This fall the Arctic icecap reached its summer minimum, which appears to be the sixth lowest on record.

There isn’t much more to say, except maybe “glub!”.  (“I’ll keep it to myself. Until the water reaches my lower lip, and then I’m gonna mention it to SOMEBODY!”)

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1. Maria–José Viñas and Mike Carlowicz, Arctic Sea Ice Reaches 2018 Minimum, in NASA Earth Observatory. 2018. https://earthobservatory.nasa.gov/images/92817/arctic-sea-ice-reaches-2018-minimum

 

The Ice is Melting

We are now in the first years of the Anthropocene, which future geologists will detect in a variety of signatures in the rocks. Massive migrations and extinctions of thousands of species, sediments filled with plastics, hydrocarbons, and other unusual chemicals, and, above all else, the loss of ice and rise of sea levels

When I was younger, I expected these things to happen long after I was dead. But maybe I will live to see the ice melt after all.

This summer we have seen yet more indications that all the ice on Earth is melting, at an accelerating pace.

We’ve been watching the crack in the Larsen C Antarctic ice shelf . (Larsen A and B have already broken up.) After years of dormancy, a huge piece broke off, now termed the A-68 iceberg. Much of the information is from Earth Observing satellites flown by NASA and ESA.

This event in itself isn’t necessarily unusual or significant. As Maria-Jose Viñas reports, large pieces of ice break off all the time. [1] So far, there is no indication that there will be a further disintegration or movement of the ice as happened with Larsen A and Larsen B.

A large reduction in the ice shelf would reduce the pressure holding the inland glaciers, possible allowing them to flow more rapidly into the sea. So, though this event doesn’t directly point to higher sea levels, it may indirectly open the way for faster melting of Antarctic ice. Researchers will continue to monitor the area with satellites and possibly other measurements.

Meanwhile, up north (everything is ‘up north’ from Antarctica), long term satellite observations indicate that not only is the ice melting, but the ice is getting darker.

For one thing, the is soot and other pollution that has blown in from the continents. Researchers are also observing an increase in algae growing in the ice, which absorb a lot more sunlight that clean white snow and ice [2]. Warming temperatures encourage algae, algae warm the surface. It’s a positive feedback loop, speeding the melting.

Another report indicates that decades of satellite observations show that there has been a decrease in cloud cover in the last twenty years [1]. This means that more and stronger sunlight reaches the ice, which has cause most of the melting during this period.

Stefan Hofer and colleagues point out that this effect is not modelled by many climate simulations. They argue that the melting is not due to higher atmospheric temperatures themselves. Rather, warming air and sea has altered the large scale circulation, decreasing the overcast. The researchers note that this also has fed the algae that has darkened the ice.

Together, these findings add to the overwhelming evidence that Greenland’s ice cap are melting rapidly, and at an accelerating pace. There is a lot of ice up there, so it will take a while. But things are moving fast and accelerating. So who knows?

The implications are serious.   If and when Greenland’s ice melts, that is enough water to raise sea level by some 7 meters. Most of us live less than 7 meters above sea level. Glub.

Antarctica’s ice is something like 7000 meters deep in places (almost as deep as Mount Everest or the Marianas Trench). If and when it all melts, it could raise seal levels 100 meters or more. Glub, glub. Even if only part of Antarctica melts (e.g., glaciers near the coast speed up dramatically), it would be many meters of sea rise.

Basically, the ocean is coming, and it may be sooner than anyone thinks. This will be one of the key markers for the Anthropocene: a sudden and gigantic rise in sea levels around the world.

Noone can say generation haven’t made our mark on the world!

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1. Stefan Hofer, Andrew J. Tedstone, Xavier Fettweis, and Jonathan L. Bamber, Decreasing cloud cover drives the recent mass loss on the Greenland Ice Sheet. Science Advances, 3 (6) 2017. http://advances.sciencemag.org/content/3/6/e1700584.abstract
2. David Shukma, Sea level fears as Greenland darkens, in BBC News – Environment. 2017. http://www.bbc.com/news/science-environment-40686984
3. Maria-Jose Viñas, Antarctic Ice Shelf Sheds Massive Iceberg, in NASA’s Earth Science News. 2017. https://www.nasa.gov/feature/goddard/2017/massive-iceberg-breaks-off-from-antarctica

 

Space Saturday

 

These reports suggest some great Names for a band:

“As Greenland Darkens”
“Recent Mass Loss”
“Larsen C”

Ice Retreating Everywhere

Twenty years ago I was happy to collaborate with the NASA Earth Observatory folks, to ramp up a long term, continuous, global record of the Earth, especially the Earth’s climate. My own part was miniscule, but I feel a bit of pride in the quality and importance of the science that continues to roll in.

Yet more remote sensing data from satellites this month documents the melting of the Northern ice cap. As summer ends, it appears that this year tied for the third lowest summer minimum, not quite a low as 2012. Having a similar result for the winter maximum, this year is on course for another near record low. Even in the time the current satellites have been in orbit, we have seen a dramatic speed up.

At the other end of the Earth, spring is coming to Antarctica. The picture there is more complex, with some areas of ice thickening, others thinning, and a possible increase in calving, as glaciers and shelves break up in the warmer sea.

This month satellite observations show rapid change in a crack that may develop into a large calving event. Bearing in mind that this is end of the cold winter months, the growth of the crack means something big is going on there. The satellite coverage means that this event will be observed from the start.

Growing Crack in Antarctica’s Larsen C Ice Shelf Spotted by NASA’s MISR Image credit: NASA/GSFC/LaRC/JPL, MISR Team

Obviously, one crack is only a small event. But the interactions of ice and ocean are really important, and may well be critical to the future of the Southern ice cap, and the fate of life on Earth. If that ice cap melts (and I’m betting it will), sea level will rise 10s of meters everywhere. That will flood most human cities and huge areas of land, and basically change the face of the planet and life on land.

Anyway, these are some nice results from a project that I admire.

Well done.

 

Space Saturday