Arctic Sea Ice 2015 - Update 10

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 and currents. 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.

The big melt in Greenland and the Arctic in general is causing further problems. Isostatic adjustment following melting can contribute to seismic events such as earthquakes, shockwaves and landslides that can destabilize methane hydrates contained in sediments on the Arctic Ocean seafloor.

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.

The water of the Arctic Ocean is very warm, not only at the surface, but even more so underneath the surface. What has...
Posted by Sam Carana on Tuesday, September 22, 2015

August 2015 Had Highest Sea Surface Temperature on Record

Across the oceans, the August 2015 globally-averaged sea surface temperature was 0.78°C (1.40°F) above the 20th century average—the highest temperature for any month in the 1880–2015 record. NOAA analysis further shows that in August 2015, the sea surface on the Northern Hemisphere was 1.02°C (1.84°F) warmer than it was in the 20th century, as illustrated by the graph below.

As the image below shows, the August data for sea surface temperature anomalies on the Northern Hemisphere contain a trendline pointing at a rise of 2°C (3.6°F) well before the year 2030. In other words, if this trend continues, the Northern Hemisphere sea surface will be 2°C (3.6°F) warmer in about a dozen years time from now.

Such a temperature rise would be catastrophic, as there are huge amounts of methane contained in the form of hydrates and free gas in sediments under the Arctic Ocean seafloor. A relatively small temperature rise of part of these sediments could cause a huge abrupt methane eruption, further speeding up local warming and triggering further methane eruptions, in a spiral of runaway warming that will cause mass destruction and extinction, as described in the reference page The Mechanism.

The situation is dire and calls for comprehensive and effective action, as discussed at the Climate Plan page.

August data for sea surface temperature anomalies on the Northern Hemisphere contain a trendline pointing at a rise of 2...

Posted by Sam Carana on Sunday, September 20, 2015

Arctic Sea Ice Collapse Threatens - Update 9

The image below shows that Arctic sea ice had reached a level of 4.45 million square kilometers on September 16, 2015 (end of dark blue line at center of image).

NSIDC has meanwhile called the 2015 minimum, but the first sentence of their post hastens to add that on September 11, Arctic sea ice reached its likely minimum for 2015,  at 4.41 million square kilometers (1.70 million square miles), putting 2015 in the fourth lowest place since satellite records began. Arctic sea ice minimum was lower only in 2012 (dotted line), 2007 (light blue line) and 2011 (orange line). Sea ice extent was 4.413 million square kilometers both on September 9, 2015, as well as on September 10 and 11, 2015.

September 9 would be early for the sea ice to reach its minimum, as a comparison with earlier years on above image illustrates. The dark blue line on above image shows that sea ice extent fell slightly on September 16, compared to the day before, and is now below the 2011 extent (orange line) for this time of the year. Over the next few days, sea ice extent may well fall somewhat further, and reach a level below the 2011 minimum, thus reaching the third lowest minimum extent since record began. This could eventuate due to winds compacting the sea ice.

More importantly, sea ice thickness is still falling, as illustrated by the image below showing the sea ice thickness on September 9 in the left panel and a forecast for thickness on September 24 in the right panel.

The image below compares sea ice thickness between September 24, 2012 (left panel) with that forecast for September 24, 2015 (right panel).

Above image illustrates why the situation in 2015 is even more threatening than it was in 2012. Only the ice that is colored light green, yellow and red is more than 3 meters thick. In 2015, ocean heat has been melting the sea ice from underneath. So, even while the currently lower temperatures of the air may have resulted in a slight increase in extent over the past week, the added ice is very thin. Ocean heat first of all goes into melting the thickest sea ice, i.e. the parts that are meters below the surface. This because the water at surface level is colder than the water underneath the surface. This explains why much of the water surface will remain covered by (very thin) ice as air temperatures are now falling (compared to air temperatures over the past few months).

The image below shows sea surface temperatures as at September 17, 2015.

In conclusion, while the sea ice appears to have survived the 2015 melting season without collapsing, the threat that this will occur in the coming years is ominous. Lack of multi-year sea ice makes that sea ice is in a very vulnerable situation. Total collapse of sea ice is therefore more likely to happen in the coming years. Every time ocean heat will arrive in the Arctic Ocean at its fullest strength in future, this heat will no longer be able to be fully absorbed by the process of melting thick sea ice, so what's left of the sea ice will melt very quickly.

There is a strengthening El Niño, while more open water increases the chance that storms will develop that will push the last remnants of the sea ice out of the Arctic Ocean, as discussed in earlier posts such as this one. Storms can also mix warm surface waters all the way down to the seafloor, as discussed in this earlier post. Cyclones that emerge with greater force due to high sea surface temperatures further increase this danger.

The big danger is that ocean heat will cause methane contained in sediments on the Arctic Ocean seafloor to be released abruptly in large quantities, triggering further methane releases spiraling into runaway warming.

The situation is dire and calls for comprehensive and effective action, as discussed in the Climate Plan.

Below is a text-only version of this post for radio.

Sea ice thickness on September 24, 2012 (left panel) compared to a forecast for September 24, 2015 (right panel). This...
Posted by Sam Carana on Friday, September 18, 2015

3.27°C warmer by 2030?

Will it be 3.27°C warmer by the year 2030?

In December 2015, world delegates will descend on Paris to ensure that global warming will not cross the guardrail of 2°C above pre-industrial levels.

[ click on images to enlarge them ]

In a way, we have already crossed this guardrail. NOAA data show that the year-to-date land surface temperature was 1.47°C above the 20^th century average on the Northern Hemisphere in 2015, as illustrated by the image on the right.

Granted, there was less warming on the Southern Hemisphere, so the globally-averaged land surface temperature was a little bit lower, i.e. 1.34°C above the 20^th century average. For reference, the image below on the right gives an overview of mean 1901-2000 temperatures. Anyway, the difference between hemispheres is small and not very relevant since most people live on the Northern Hemisphere.

[ click on image to enlarge ]

More importantly, this 1.47°C rise is a rise compared to the 20^th century average. The 20^th century average was some 0.60°C higher than temperatures were at the start of the NOAA record in 1880. In other words, temperatures for most people on Earth are already 2.07°C higher than they were in 1880.

Furthermore, between 1750 and 1880 the global average temperature had already increased by some 0.20°C.

Sure, 2015 is an El Niño year, but this El Niño is still strengthening, so 2016 could well be even warmer. Moreover, recent temperatures are in line with expectations of a polynomial trendline that is based on these NOAA data and that points at yet another degree Celsius rise by 2030, on top of the current level, as illustrated by the top image. Altogether, this would make it 3.27°C warmer than in 1750 for most people on Earth by the year 2030.

So, instead of acting as if dangerous global warming could possibly eventuate beyond the year 2100, delegates in Paris should commit to lowering temperatures, starting now.

To lower temperatures, cutting emissions alone will not be enough.

Stopping all emissions by people would make that the aerosols that are currently sent up in the air by burning fuel and that are currently masking the full impact of global warming, will fall out of the air in a matter of weeks. Until now, about half of the global temperature rise is suppressed by such aerosols. Stopping aerosols release overnight could make temperatures rise abruptly by 1.20°C in a matter of weeks.

Furthermore, carbon dioxide that is emitted now will take ten years to reach its peak impact, so we're still awaiting the full wrath of carbon dioxide emitted over the past decade.

A recent study calculates that global mean surface temperature may increase by 0.50°C after carbon emissions are stopped, and they will decrease only minimally from that level for the next 10,000 years.

Removing carbon dioxide from the atmosphere would not work fast enough to avoid further warming and acidification of the oceans. In fact, temperatures look set to rise even faster as feedbacks start to kick in more fully, such as albedo changes due to decline of the snow and ice cover in the Arctic and methane releases from the Arctic Ocean seafloor. Furthermore, water vapor will increase by 7% for every 1°C warming. Water vapor is one of the strongest greenhouse gases, so increasing water vapor will further contribute to a non-linear temperature rise.

In conclusion, the world needs to commit to comprehensive and effective action that includes both emission cuts and removal of greenhouse gases from the atmosphere and oceans, as well as further action to deal with the dire situation in the Arctic, as discussed at the Arctic-news Blog.

In December 2015, world delegates will descend on Paris to ensure that global warming will not cross the guardrail of 2°...
Posted by Sam Carana on Thursday, September 10, 2015