Misconceptions on Antartica Ice

Deniers keep citing evidence of increasing sea ice around Antarctica as evidence that global warming is not real. So, let’s review the facts.

Antarctica sea ice is increasing. Take look at this plot:

Source: NSIDC

This shows the annual extent of sea ice in May every year up to this year (the last complete month). Keeping in mind the seasons are opposite in the south, this represent the ice extent as the region is approaching the heart of winter. You can see that there is a trend of increasing ice and this last May, (the last plus mark on the right) was the highest ice extent ever recorded.

At this point deniers are going, “See, we told you so!” and this would be just one more example of how deniers ignore anything they don’t want to see.There are major differences between the Arctic and the Antarctic. See a discussion about this from NSIDC here.  Among those differences are the circumpolar currents in the atmosphere and the oceans that isolate Antarctica and make it a unique environment. Another difference is even bigger – land ice. Deniers conveniently ignore the fact that Antarctica is the largest reservoir of land ice in the world. What is going on with the land ice?

The reality is that Antarctica is losing ice in large amounts. One of the reasons sea ice is increasing is because it is coming from the land ice that is sliding into the ocean. Evidence indicates is losing land ice at a rate of over 100 billion tons a year. That is enough to raise the sea level in excess of a millimeter per year. That may not sound like much, but in ten years that amounts to a one-centimeter rise in world sea levels and that does not include other sources of sea level rise.

A NASA/ESA study incorporating more satellite data than past studies confirmed that both Greenland and Antarctica are losing ice mass.

The loss of land ice is increasing and it was recently determined that the massive West Antarctica Ice Sheet has reached the point of no return. Even if we stopped emitting greenhouse gases today, the ice sheet will still melt.

The evidence is conclusive, the total amount of ice in the Antarctic region is decreasing, not increasing.

So, if deniers want to talk about ice in the Antarctic region, make sure they include the land ice. Its a very different story when you do.

The Great Arctic Ice Recovery of 2013

One of the more common claims deniers make is that the Arctic sea ice recovered in 2013 and that the issue of the vanishing Arctic sea ice is no longer valid. Frequently, this issue is pulled out as evidence that global warming is not real, or at least over blown.

Let’s look at the facts to see the validity of these claims.  Below is a plot from the National Snow and Ice Data Center (NSIDC) showing the amount of Arctic sea ice. The solid black line is the long-term average. The dotted line on the bottom is the data from 2012, which was a catastrophic year and, by far, the year with the lowest amount of sea ice. The line in between those two is the data from 2013. As you can see, the ice made a recovery, but not even to the average.

Source: NSIDC

To put it another way, look at this similar graphic. This time we still have the long-term average as the black line, but the two lines below it represent the data for 2013 and for 2009. The 2013 ice data is very similar to the 2009 levels. In other words, the ice in 2013 recovered to only about the 2009 level.

Source: NSIDC

What does that mean when I say it recovered to 2009 levels? Take a look at this plot of the September sea ice extent (annual minimum extent) over time.

ftp://sidads.colorado.edu//DATASETS/NOAA/G02135/Sep/N_09_plot.png
Source: NSIDC

You can easily see the big dip in 2012 and the recovery that occurred in 2013 as the last two data points on the right. Start at the 2013 data point (the last plus mark) and make a horizontal line to the left to compare it to previous years. You can see it is about the same as 2009. Otherwise, there are only five data points that are lower and that is going back all the way to 1979.

There is a clear downward trend to the plot above, but the individual years go up and down. There is nothing surprising about that. We can see that 2012 was an abnormally bad year. Likewise, 2013 was a nice recovery that we hope will continue. But, you can’t make judgements about the trend based on one, or even two years. If scientists were to make claims based on just 2012 alone, it would be as wrong as deniers making claims based on 2013 alone. The long-term trend is what is important.

So, will the trend continue in 2014, or did 2013 represent the start of a new trend? Let’s look. Below is a plot showing the ice data for this year (as of June 28). Again, the long-term average is the black line. The complete curve is for 2013 and the partial curve is for what has happened so far this year.

Source: NSIDC

The ice data for this year is consistently tracking at below last year’s. Granted, it is only a little bit below and there is a lot of melt season remaining, so there could be some significant changes in this graph by September. Remember, though, those significant changes could go either way. The point I’m making here is that we are not seeing evidence of a recovery, we are seeing evidence that the data is returning to the trend line.

Look at this plot.This is the ice surface temperature and comes from the Danish Polar Portal. The North Pole is located in the middle of the figure. The color of the ice represents the temperature according to the scale on the bottom. The white areas are areas where data was not collected due to cloud cover. The coldest areas are typically north of Greenland, where the large white area is in this plot. But, the rest of the Arctic region is either close to 0 degrees Celsius or above. In other words, its melting.

Source: Polar Portal

This temperature distribution is about average for this time of year and there is thickness to the ice, so we are not looking at some major collapse of the sea ice. But, the evidence does not support claims that the sea ice extent has recovered. I hope it does recover because this is a critically important part of the world in regards to weather. The data, though, is indicating the reduction in sea ice extent will continue pretty close to the long-term trend.

I will post updates as the melt season continues.

Forest Fires and Arctic Melting

The summer melt season of 2012 was very dramatic. Take a look at this plot from the National Snow and Ice Data Center (NSIDC).

The dark, solid line is the 1989-2010 average Arctic sea ice extent. The dotted line is the 2012 sea ice extent. The light gray line on the left is the 2014 sea ice extent. We can see from this plot that the 2012 extent was pretty average for what has been observed this century all the way up to early-June. At that point, it took a severe turn for the worse and the extent simply collapsed, reaching the all time record low in September.

Something similar was observed in Greenland at the same time. Normally, the ice on top of the ice sheet doesn’t melt, or melts very little. It is over 2 miles high in places and the highest elevations remain below freezing, even during the summer. But, in the summer of 2012, 97% of the ice sheet was melting at one time. This was the most extensive melting event since 1889.

A new study done by researchers at Dartmouth College found evidence that this extensive melting on Greenland was not due solely because of global warming, but by a combination of warming and soot from wildfires. In particular, extreme forest fires in Siberia sent soot and particulate matter high in the atmosphere and some of that matter settled on the Greenland ice sheet. By making the ice slightly darker (known as lowering the albedo), the soot increased the amount of sunlight absorbed by the ice and increased the melting. There is evidence something similar may have occurred in 1889, as well.

The question I now have is, did this also happen to the sea ice? The fires of 2012 may have been responsible for the Greenland melting, but wouldn’t explain the sea ice melting. The fires didn’t start until July, so the smoke could not have been on the sea ice at the beginning of June. The smoke was blowing across the Pacific by early-July, so it is possible it fell on Greenland in time for the big ice melt.

However, there were also massive forest fires in Siberia two years earlier, in the summer of 2010. If the smoke from those fires was lofted high in the atmosphere it might have taken over a year to fall in the Arctic region. We would need to get some ice cores that included that time frame and see if there are traces of soot in the ice. Then, we would need to check the composition of that soot to try and identify where it came from.

This doesn’t mean climate change is off the hook. Even with the soot, global warming is responsible because it made the Arctic region warmer (allowing the ice to melt) and it is also responsible for the events in Siberia that led to the wildfires (putting the soot in the air).

This year might be a test of the hypotheses. If it took 1-1/2 to 2 years for the 2010 smoke to get to the Arctic ice, then that would be a good starting guess for how long it took the smoke from the 2012 fires to get there. If so, this might be a very bad year for Arctic sea ice melting.

Arctic Sea Ice and the Atlantic Multidecadal Oscillation

The Atlantic Multidecadal Oscillation (AMO) is a naturally occurring 60-90 year cycle in sea surface temperatures in the North Atlantic. This cycle consists of alternating cold and warm periods and has an influence on the climate in the region. A recent paper by Martin W. Miles, et al, examines the history of ice extent in the area and compares it to the AMO record. What they found is that ice extent in the region fluctuates in response to the changes in the AMO, resulting in periods of greater and lesser ice extent. They suggest that some of the unprecedented loss of sea ice in the recent decades can be tied to a warm cycle in the AMO.

I have no problem with this. I would expect there to be just such a naturally occurring cycle. But, I do not find this to be enough to explain what we have been witnessing, and the authors emphasize that this in only a part of the puzzle and there are other factors, including warming from manmade emissions, that are contributing to the ice loss.

Take a look at the ice anomaly for September 2012:

And the ice extent for the same month:

The Barents Sea is the area on the right, between Norway and the polar sea ice. With the North  Pole marked in both images, it is the area at about the 4-5 o’clock position. Comparing the two figures, we can see this region has experienced a great deal of sea ice since 1980. Can the AMO explain all of this loss? I would be not, but let’s say that it is still under study.

But, what about the rest of the Arctic Ocean? There is significant loss all around the North Pole and this cannot be explained by the AMO. So, before we get all excited that maybe the loss of the Arctic sea ice is just a naturally occurring event, we can already see that it may be contributing to the recent loss, but it cannot explain for all of it. After all, we never saw the level get this low in previous warm cycles. And, the current loss began during a cool cycle. Clearly, there is more to the ice loss than the AMO.

2014 Arctic Sea Ice Maximum has Passed

It isn’t official yet, but it will be soon. The maximum extent of Arctic sea ice passed in the last week or two. Take a look at these two figures. The first is the daily Arctic sea ice extent as plotted by the National Snow and Ice Data Center. The second is the surface temperature in the Arctic region and was obtained from the Polar Portal. We can see from the first plot that the amount of ice extent is decreasing. Fluctuations are normal and expected, but the second figure shows that the surface temperature of the ice along the fringes is above freezing, so no new ice will be forming.

Source: NSIDC
Source: Polar Portal

Unfortunately, it looks like bad news for the Arctic sea ice this year. There is a long melt season ahead of us, so nothing is for certain. However, we are starting off badly. The level of sea ice this year is significantly below the 2012 level. This is important for two reasons. The summer of 2012 led to the lowest level of Arctic sea ice ever recorded, and this level was much lower than anything measured before. The second reason the 2014 levels are significant is because there was a large rebound of Arctic sea ice last year – a 60% rebound. Many people have been hoping this rebound would lead to increased levels of ice going into the future and slow down the climate change effects occurring in the Arctic region. However, even with the big 60% rebound, we see the extent levels for this year are starting out much lower than in recent years.

Hopefully, the melt rate will be slow this summer and we won’t see a recurrence of 2012, but I don’t feel good about the chances.

Confirmed! Arctic Winter Was Warm

The National Snow and Ice Data Center has confirmed that temperatures in the Arctic this winter were above average. Not surprisingly, the amount of ice cover is also way down, stating:

Arctic sea ice extent in February 2014 averaged 14.44 million square kilometers (5.58 million square miles). This is the fourth lowest February ice extent in the satellite data record, and is 910,000 square kilometers (350,000 square miles) below the 1981 to 2010 average.

A check of the daily plot of the ice extent shows that the ice extent is significantly lower than the 2012 level at this time of year. The significance is that, while 2012 was not the lowest February level (that occurred in 2005), 2012 ended up having, by far, the lowest minimum ice extent in September. This is not to say that this years minimum will be even less than 2012, but it is certainly a red flag. A particularly troubling observation is that the level is below the two standard deviations mark. That means the level is out of the range of statistical uncertainty relative to the long-term average. Just as in some public opinion polls, scientific figures come with a plus-or-minus uncertainty along with the reported value. (That should not be a surprise because public opinion polls are scientific figures.) The solid line at the top of the below figure is the long-term average. The shaded region is the plus-or-minus amount that goes with it. We can see that the current level is below that uncertainty value.

We should we care? Why have I made several postings about the sea ice extent? The Arctic region is the most sensitive to climate change. The observed temperature change is the Arctic region far outpaces what we have seen in the rest of the world. This, of course, is major fly in the ointment to those people that claim measured temperature increases are due to the heat island effect. The region experiencing the most temperature increase is the region that has no heat islands. Bad for the deniers. Unfortunately, it is also bad for the rest of us. Much of our climate is governed by what goes on in the Arctic, including air and ocean currents. The ice of the polar caps reflect sunlight with great efficiency. But, open water absorbs sunlight with great efficiency. When the ice caps melt the region goes from a sunlight reflector to a sunlight absorber. This will increase the temperature rise and will have many impacts on the way the atmosphere and ocean currents behave.

There are those that say we should allow global warming because we can benefit from the change. This really is not likely, but it is a pretty silly bet. Are you willing to bet your well-being and the well-being of your children on that, when the science says otherwise? Remember, this is not something we can take back. Once we make these changes it will take centuries to undo them.

Think about all of that every time you put an ice cube in your drink to cool it down.