Antarctic sea ice hit 35-year record high Saturday

Antarctic sea ice extent on September 22 compared to 1981-2010 median depicted by orange curve (NSIDC)

Antarctic sea ice has grown to a record large extent for a second straight year,
baffling scientists seeking to understand why this ice is expanding
rather than shrinking in a warming world
.
On Saturday, the ice extent reached 19.51 million square kilometers,
according to data posted on the National Snow and Ice Data Center Web site.

That number bested record high levels set earlier this month and in 2012
(of 19.48 million square kilometers). Records date back to October 1978.

(NSIDC)

The increasing ice is especially perplexing since the water beneath the ice has warmed, not cooled.

“The overwhelming evidence is that the Southern Ocean is warming,” said Jinlun Zhang,
a University of Washington scientist, studying Antarctic ice. “Why would sea ice be increasing?
Although the rate of increase is small, it is a puzzle to scientists.”

In a new study in the Journal of Climate, Zhang finds both strengthening and converging winds
around the South Pole can explain 80 percent of the increase in ice volume which has been observed.

“The polar vortex that swirls around the South Pole is not just stronger than it was when satellite records began in the 1970s, it has more convergence, meaning it shoves the sea ice together to cause ridging,”
the study’s press release explains.

“Stronger winds also drive ice faster, which leads to still more deformation and ridging.
This creates thicker, longer-lasting ice, while exposing surrounding water and thin ice
to the blistering cold winds that cause more ice growth.”

But no one seems to have a conclusive answer as to why winds are behaving this way.

“I haven’t seen a clear explanation yet of why the winds have gotten stronger,” Zhang
told Michael Lemonick of Climate Central.

Some point to stratospheric ozone depletion, but a new study published in the Journal of Climate
notes that computer models simulate declining – not increasing
– Antarctic sea ice in recent decades due to this phenomenon (aka the ozone “hole”).

“This modeled Antarctic sea ice decrease in the last three decades is at odds with observations,
which show a small yet statistically significant increase in sea ice extent,”says the study,
led by Colorado State University atmospheric scientist Elizabeth Barnes.
A recent study by Lorenzo Polvani and Karen Smith of Columbia University
says the model-defying sea ice increase may just reflect natural variability.

If the increase in ice is due to natural variability, Zhang says, warming from manmade greenhouse gases should eventually overcome it and cause the ice to begin retreating.

“If the warming continues, at some point the trend will reverse,” Zhang said.

However, a conclusion of the Barnes study is that the recovery of the stratospheric ozone layer
– now underway – may slow/delay Antarctic warming and ice melt.

Ultimately, it’s apparent the relationship between ozone depletion, climate warming from
greenhouse gases, natural variability, and how Antarctic ice responds is all very complicated.

In sharp contrast, in the Arctic, there seems to be a relatively straight forward relationship
between temperature and ice extent.

Related: Arctic sea ice has *not* recovered, in 7 visuals (link below / and, posted into this posting)

http://www.washingtonpost.com/blogs...rctic-sea-ice-has-not-recovered-in-7-visuals/
(posted in below)


“And now it’s global COOLING! Record return of Arctic ice cap as it grows by 60% in a year” shouts the astonishingly misleading headline of a story by the Daily Mail’s David Rose.
It is true, that compared to last year, Arctic sea ice has bounced back some from its mind-boggling record low in 2012, 49 percent below the 1979-2000 average.

(National Snow and Ice Data Center)
But this September’s Arctic sea ice extent, now near its minimum, is not exactly prospering, some 23 percent below normal. (As of Monday, the Arctic was covered by 2.00 million square miles of sea ice, compared to the 1979-2000 average of 2.59 million square miles.)

(National Snow and Ice Data Center)
This year’s minimum should be the sixth lowest on record (since 1979), with only 2007, 2008, 2010, 2011 and 2012 having less extensive ice.

(National Snow and Ice Data Center)

(Japan Aerospace Exploration Agency)
Not only is the Arctic sea surface ice melting, but so is the ice underneath, as illustrated in this excellent visualization (hat tip: Andrew Revkin):
And in this chart:

(University of Washington)
There is no basis, based on a one-year uptick, to conclude the long-term decline in Arctic ice has ceased.


BACK TO ORIGINAL ARTICLE:

Thus, in the Antarctic, we shouldn’t necessarily expect to witness the kind of steep decline
in ice that has occurred in the Arctic.

“…the seeming paradox of Antarctic ice increasing while Arctic ice is decreasing
is really no paradox at all,” explains Climate Central’s Lemonick.

“The Arctic is an ocean surrounded by land, while the Antarctic is land surrounded by ocean.
In the Arctic, moreover, you’ve got sea ice decreasing in the summer;
at the opposite pole, you’ve got sea ice increasing in the winter.
It’s not just an apples-and-oranges comparison: it’s more like comparing apple pie with orange juice.”


Jason Samenow is the Capital Weather Gang's chief meteorologist and serves as the Washington Post's Weather Editor.

He earned BA and MS degrees in atmospheric science from the University of Virginia and University of Wisconsin-Madison.


http://www.washingtonpost.com/blogs...tic-sea-ice-hit-35-year-record-high-saturday/

 

Antarctic sea ice reaches greatest extent

so late in season, 2nd largest extent on record



By Jason Samenow

By Jason Samenow

Annual Antarctic sea extents in million square kilometers from 1979-2012 (each line represents a different year).
The current level of 16.22 million square kilometers is the highest so late in the season and second highest on record. See interactive chart. (University of Illinois Polar Research Group)Almost two weeks ago, Arctic sea ice extent shrank
to a stunning record low.

Yet, at the other end of the planet, Antarctic sea ice is nearing or breaking records for largest extent.

At face value, it’s remarkable to see such contrasting extremes in sea ice cover on opposing sides of our planet.
For those unconvinced the Earth is warming, the Antarctic ice boom provides a convenient retort to alarms sounded about the Arctic ice “death spiral.”

But, in reality, it is incredibly misleading to equate the two records. Statistically, the decline in Arctic sea ice
is much more dramatic. Further, the increase in Antarctic sea ice is not directly related to local air temperatures,
which are actually going up.

Let’s begin by examining at the state of Antarctic sea ice.

There’s no disputing it’s in record territory.

Data from the University of Illinois Polar Research Group (see chart above) show Antarctic sea ice extent
reached 16.22 million square kilometers this week (around September 25). That is not only the largest extent
ever reached so late in Antarctica’s cold season (seasons are reversed in the southern hemisphere),
but also the second largest extent logged at any time dating back to 1979, when records began.

The largest extent on record - 16.23 million square kilometers - occurred around September 20, 2007
and could be eclipsed soon.
As impressive as these numbers are in the Antarctic, they’re nothing compared to the Arctic statistics.

Antarctic and Arctic sea ice extent on September 27 indicated by the blue and orange Xs following their respective
blue curves. The black line is the 1979-2000 average and the gray shaded area bounds two standard deviations. (National Snow and Ice Data Center)

If we look at current Arctic and Antarctic sea ice extents compared to their 1979-2000 averages,
Arctic sea ice is almost 50 percent below average whereas Antarctic sea ice is just between 5 and 10 percent
above average.

It’s not that we should dismiss the Antarctic difference from average.

At some two standard deviations from (above) the mean, that signifies there’s just about a 5 percent chance
of this happening (assuming a normal distribution). But the Arctic difference from average is in an entirely different universe statistically speaking, way, way beyond two standards deviations from (below) the mean.

Arctic versus Antarctic sea ice extents in August from 1979-2012. (National Snow and Ice Data Center)

Moreover, the long term rate of decline in Arctic ice obliterates the converse rate of increase in the Antarctic.

In August, for example, Arctic sea ice is declining at a rate of 10 percent per decade since 1979
compared to an increase of 0.6 percent per decade in the Antarctic.

How does warming lead to increasing ice in the Antarctic?

Even if the decrease in Arctic ice easily trumps the increase in Antarctic ice, we still haven’t resolved the paradox
of why Antarctic sea ice is increasing if local and global temperatures are warming.

Much has been written about this in recent weeks in different articles and blogs, so I’ll just excerpt the explanations most frequently mentioned:From the Houston Chronicle SciGuy, Eric Berger:

“ Unlike the Arctic, Antarctica is surrounding by water, so its less responsive to changes in air temperatures.
Its climate is more governed by wind and ocean currents.”
See related explanation on the National Snow and Ice Data Center’s website.

From Live Science: “Another reason why the sea-ice extent in the Antarctic is remaining fairly high is,
interestingly, the ozone hole,” [Mark] Serreze [director of the National Snow and Ice Data Center] told Life’s Little Mysteries. ...

“The ozone hole affects the circulation of the atmosphere down there. Because of the ozone hole, the stratosphere above Antarctica is quite cold. Ozone in the stratosphere absorbs UV light, and less absorption [by] ozone makes the stratosphere really cold. This cold air propagates down to the surface by influencing the atmospheric circulation
in the Antarctic, and that keeps the sea ice extensive.”

• From John Cook at Skeptical Science: “Another contributor is changes in ocean circulation. The Southern Ocean consists of a layer of cold water near the surface and a layer of warmer water below. Water from the warmer layer rises up to the surface, melting sea ice. However, as air temperatures warm, the amount of rain and snowfall also increases. This freshens the surface waters, leading to a surface layer less dense than the saltier, warmer water below. The layers become more stratified and mix less. Less heat is transported upwards from the deeper, warmer layer. Hence less sea ice is melted.”

In short, the behavior of Antarctic sea ice is complex.

The general expectation is that it will take much longer for Antarctic sea ice to respond to climate warming
compared to the Arctic.

As Climate Central’s Michael Lemonick explains: “By the second half of the century, however,
climatologists say that the human warming signal will become more apparent,
and Antarctic sea ice will begin to follow its Arctic cousin in a downward spiral.


Jason Samenow is the Capital Weather Gang's chief meteorologist
and serves as the Washington Post's Weather Editor.

He earned BA and MS degrees in atmospheric science from the University of Virginia and University of Wisconsin-Madison.

http://www.washingtonpost.com/blogs...72625d8-098e-11e2-a10c-fa5a255a9258_blog.html