This seems to be, for all intents and purposed the final word for the 2015 season
Arctic Sea Ice 2015 -
Update 10
22
September, 2015
It
looks like sea ice has passed its minimum extent for the year 2015,
as illustrated by the image below.
There
are some differences between the various websites measuring extent,
such as to whether the 2015 low was the third or fourth
lowest. Japanese
measurements show
that sea ice extent was 4.26 million square km on September 14, 2015,
i.e. lower than the 2011 minimum of 4.27 million square km, as
illustrated by the image below.
Meanwhile,
the Polar
Science Center at the University of Washington has
announced that Arctic sea ice volume minimum was reached on September
12, 2015, with a total volume of 5,670 cubic km. The image below
shows a polynomial trendline based on their annual Arctic sea ice
volume minima, including this volume for 2015.
Importantly,
the sea ice in many places is now less thick than it was in 2012, as
illustrated by the image below, showing sea ice thickness on
September 27, 2012 (panel left) and a forecast for September 27, 2015
(panel right).
The
reason for the dramatic decrease in thickness of the multi-year sea
ice is ocean heat, as illustrated by the image below, showing sea
surface temperature anomalies in the Arctic as at September 21, 2015.
The
water of the Arctic Ocean is very warm, not only at the surface, but
even more so underneath the surface. What has contributed to
this situation is described by the image below. From 2012, huge
amounts of fresh water have run off Greenland, with the accumulated
fresh water now covering a huge part of the North Atlantic.
Since
it's fresh water that is now covering a large part of the surface of
the North Atlantic, it will not easily sink in the very salty water
that was already there. The water in the North Atlantic was very
salty due to the high evaporation, which was in turn due to high
temperatures and strong winds. As said, fresh water tends to stay on
top of more salty water, even though the temperature of the fresh
water is low, which makes this water more dense. The result of this
stratification is less evaporation in the North Atlantic, and less
transfer of ocean heat to the atmosphere, and thus lower air
temperatures than would have been the case without this colder
surface water.
Meanwhile,
global warming continues to heat up the oceans, while less of this
ocean heat can now be transferred from the water to the atmosphere in
the North Atlantic, since the fresh water is acting like a lid.
The
danger is thus that warmer water will be pushed into the Arctic Ocean
at lower depth, and that it will reach the seafloor of the Arctic
Ocean where huge amounts of methane are contained in sediments. Ice
acts like a glue, holding these sediments together and preventing
destabilization of methane hydrates. Warmer water reaching these
sediments can penetrate them by traveling down cracks and fractures
in the sediments, and reach the hydrates.
In the video below,
by Nick
Breeze,
Professor Peter Wadhams discusses the situation.
The
situation is dire and calls for comprehensive and effective action as
discussed at the Climate Plan.
There are some differences between the various websites measuring extent, such as to whether the 2015 low was the third or fourth lowest. Japanese measurements show that sea ice extent was 4.26 million square km on September 14, 2015, i.e. lower than the 2011 minimum of 4.27 million square km, as illustrated by the image below.
Meanwhile, the Polar Science Center at the University of Washington has announced that Arctic sea ice volume minimum was reached on September 12, 2015, with a total volume of 5,670 cubic km. The image below shows a polynomial trendline based on their annual Arctic sea ice volume minima, including this volume for 2015.
Importantly, the sea ice in many places is now less thick than it was in 2012, as illustrated by the image below, showing sea ice thickness on September 27, 2012 (panel left) and a forecast for September 27, 2015 (panel right).
The reason for the dramatic decrease in thickness of the multi-year sea ice is ocean heat, as illustrated by the image below, showing sea surface temperature anomalies in the Arctic as at September 21, 2015.
The water of the Arctic Ocean is very warm, not only at the surface, but even more so underneath the surface. What has contributed to this situation is described by the image below. From 2012, huge amounts of fresh water have run off Greenland, with the accumulated fresh water now covering a huge part of the North Atlantic.
Since it's fresh water that is now covering a large part of the surface of the North Atlantic, it will not easily sink in the very salty water that was already there. The water in the North Atlantic was very salty due to the high evaporation, which was in turn due to high temperatures and strong winds. As said, fresh water tends to stay on top of more salty water, even though the temperature of the fresh water is low, which makes this water more dense. The result of this stratification is less evaporation in the North Atlantic, and less transfer of ocean heat to the atmosphere, and thus lower air temperatures than would have been the case without this colder surface water.
Meanwhile, global warming continues to heat up the oceans, while less of this ocean heat can now be transferred from the water to the atmosphere in the North Atlantic, since the fresh water is acting like a lid.
The danger is thus that warmer water will be pushed into the Arctic Ocean at lower depth, and that it will reach the seafloor of the Arctic Ocean where huge amounts of methane are contained in sediments. Ice acts like a glue, holding these sediments together and preventing destabilization of methane hydrates. Warmer water reaching these sediments can penetrate them by traveling down cracks and fractures in the sediments, and reach the hydrates.
In the video below, by Nick Breeze, Professor Peter Wadhams discusses the situation.
The situation is dire and calls for comprehensive and effective action as discussed at the Climate Plan.
I would just add the following, from Harold Hansell
Arctic Sea Ice 09 21 2015 with pink for sea ice concentration of 15 % or less. I am thinking that what I am seeing is Arctic sea ice that has had most of it undermined by warm water
I'm always amazed at how calm these scientists seem to stay while describing the probable cause of our demise. As I have suspected, the ice held on this year, by a small margin, but next year could be a very different story,
ReplyDeleteThe ice cap is entering winter very thin & as he said, it would take just one storm to send much of that ice down the east side of Greenland & into the Atlantic.