But, What About Antarctica?

Finishing out the big three ice reservoirs, let's talk about what is happening in Antarctica.

Now, first a word about the difference in the Greenland Ice Sheet (GIS) and the Antarctic land ice. The Arctic sea ice is just what it says, it is frozen ocean floating on top of the water. There are all sorts of important things about the sea ice, but one thing it does not affect is the sea level. The sea ice is already in the water and it will not affect the sea level when it melts. The GIS and the Antarctic ice sheets are not in the water - they are on land. As they melt, the water runs off into the oceans and is partly responsible for the rising sea level observed worldwide (heating the water also causes the sea level to rise). The more they melt in the future, the more the sea level will rise. We saw yesterday the GIS is melting at an alarming rate and that rate is continuously increasing. Now, let's turn our attention to Antarctica.

Unlike Greenland, Antarctica has two major ice sheets - the West Antarctic Ice Sheet (WAIS) and the East Antarctic Ice Sheet (EAIS). These two ice sheets combined are unbelievably large. The GIS, the second largest ice sheet in the world, is about 2.8 million cubic kilometers and covers an area three times the size of Texas. If all of that ice were to melt it would raise the world's sea level by about 7.2 meters. In comparison, the EAIS and WAIS combined have about 30 million cubic kilometers, more than ten times the volume of the GIS. The Antarctic ice covers an area greater than the continental U.S. and Mexico combined. If all of that ice was to melt it would raise the sea level by about 70 m. Together, these ice sheets contain 99% of all of the fresh water ice on the planet.

Now, I give those statistics to provide an idea of the mass of these ice sheets. I am in no way suggesting any of these three ice sheets are at risk of completely melting within the next few hundred years. But, what if only 10% were to melt? That would result in a rise in the sea level of about 7.7 meters (25.26 feet) and that would be enough to inundate every coastal area of the world. What if only 5% were to melt within the foreseeable future? That is still enough to drown all coastal areas with about 3.9 meters (12.8 feet) of sea level rise. The point is, we don't need a catastrophic failure of the ice sheets to have a catastrophe. For this reason, it is extremely important for us to pay attention to the ice sheets. There is no turning back at this point. The sheets will melt and we will have to pay many trillions of dollars as a result as the coasts are drowned. The question is, just when are we going to have to pay? Of course, Southern Florida is already being drowned.

So, we understand the state of the ice in Antarctica is important, but just what is the state of those ice sheets?

People skeptical of climate change frequently claim the total ice mass is increasing. This is a false claim. The total ice mass around the world is decreasing and decreasing at an alarming rate. However, they are correct if they limit their claim to Antarctic sea ice. This is a plot of the southern sea ice trend for September, the month of maximum extent in the south:

Source: NSIDC

This would be reassuring, if that were all there was to the story. Unfortunately, most of that ice melts in the southern summer, reaching a minimum of about 4.4 million square kilometers in March every year. Also, this plot is for only the sea ice and does not include the land ice. Here is a comparison plot of the mass for the both the GIS and the Antarctic ice:

Source: Penn State University Department of Geosciences

Comparison of these two plots shows bad news, good news, and more bad news.

The first bad news is obvious. The ice sheets in both Greenland and Antarctica are losing mass, i.e., they're melting. This is not good due to the data I provided above. Melting land ice raises sea levels and the two largest reservoirs of ice on land are both melting.

The good news is that Antarctica is not melting at fast as Greenland. Draw a tangent line and you can see the line for the Greenland data has a steeper slope than the line for the Antarctica data.

But, that brings up the second batch of bad news - the slope on both is increasing. This means the rate of melting for both land masses is increasing. That is really bad news.

The EAIS is gaining mass due to an increase in snow fall. Unfortunately, at the same time, the melting of the WAIS is accelerating. The melt increase in the west is more than enough to offset the snowfall gain in the east. The result is a net mass loss, and one that is increasing in rate. In fact, the loss rate in the west has doubled in the last six years.

So, while the winter sea ice extent has been increasing in recent years, the land is losing about 90 Gtons of ice per year. The complete picture is that the southern continent is losing ice - and it is losing it at an increasing rate.

Meanwhile, In Greenland...

I have been discussing the Arctic sea ice a lot lately and haven't really mentioned land ice. The reason is pretty simple - there's lots of data on the Arctic sea ice and it is very dynamic up there. There isn't as much data on Greenland and Antarctica and it takes a long time to see a change in either. Having said that, let's take a look at Greenland and see what's going on there.

This is a plot, courtesy of the Polar Portal, showing this year's melt for the Greenland Ice Sheet (GIS):

Source: Polar Portal

The top panel shows the daily GIS mass change since September 2014. The grey line in the middle is the long term average seasonal mass change. The mass increases during the winter as the ice sheet accumulates snow. Then, as the melt season commences (late-May to early-June), there will be some melting and runoff, resulting in a loss of mass. This is to be expected and there is no controversy here. What we want to know is if there is any change in the seasonal process over a period of time. The bottom panel helps answer that question and we can see this year's melt season is significantly below the long-term average. The red line is the melt season for 2012, the disastrous year for ice melt.

So, 2015 is way below average, but you could argue it has 'rebounded' from 2012 and is increasing. Okay, fair enough. Let's take a look of the long term mass balance (again, courtesy of the Polar Portal):

Source: Polar Portal

This clearly shows the total mass balance (i.e., how much ice there is) is not only on a most definite downward trend, but we can see very easily that the rate of loss is increasing. Draw a tangent line for the period of 2003 through 2009. Then, draw another tangent line for the period of 2010 through 2014. The second line will have a much steep slope than the first, meaning the downward trend has been greater since 2010 than it was before that year.

Clearly, things are not going well. We don't need to go any further than this to understand the GIS is melting and it is melting at an ever increasing rate. This is very serious news for climate change and global sea levels. But, if you want more, read this article to see just how bad it truly is. Spoiler alert: It's much worse than we thought.

Greenland is Melting Differently

I was reading a report about a presentation at the American Geophysical Union (AGU) meeting in San Francisco last week. Lora Koenig, a glaciologist at the National Snow and Ice Data Center (NSIDC) led a group that found the way ice is melting on the Greenland Ice Sheet changed during the 1990s. The principle means of melting used to be glaciers calving off into the sea. What Koenig's group found is that, while the glacial flow continues, melt ponds have now become the dominant means of mass loss. The ice will melt during the summer and forms bodies of water that range from small ponds to large lakes. This water finds ways to get through the ice and rivers of melt water form. Some of these ponds are even staying liquid through the winter with a layer of insulating snow on top. This provides a jump start on the next melt season. Additionally, the conditions have changed to allow even more melt water to run off. The top layer of snow used to absorb a lot of melt water, but it has now absorbed so much in some places that it is saturated and freezes solid. Since the snow can no longer absorb the melt water, the water flows over the surface and eventually goes into the sea.

So, if the climate isn't changing, as the denier industry wants us to believe, then why is the means of melting changing on something as large as the Greenland Ice Sheet?

Greenland Mass Loss is Bad and Getting Worse

Greenland is melting, which is not good. Recent studies indicate it is even getting worse, too. Take a look at the mass of the Greenland Ice Sheet (GIS) and see what has been going on. This is plot of the GIS mass and comes from the Danish Polar Portal site:

Source: Polar Portal

This graph is of data obtained by the GRACE satellite and shows the change in mass due to the small change in the gravity field. It is easy to see the total mass of the the GIS is declining. The upticks in the graph show the mass is growing in the winter and the down ticks show the mass is declining in the summer. Hopefully, that is not a surprise nor should there be any controversy with that. But, what we see is that over a period of time the mass is decreasing more during the summer melt season than it is growing during the winter freeze season. As a result, the overall mass is decreasing on an annual basis.

But, there is something even more significant. Take a trend line for the period of about 2003 - 2009. Then, take another trend line for the period of 2010 - 2014. The second trend line is much steeper than the first. That means the rate of decline was much greater in the second period than in the first. Is the rate of decline accelerating? The data suggests it is and is something we will need to monitor. But, it gets worse.

A recent study used NASA laser altimeter data to study the entire surface of the ice sheet. That study found the estimate of mass loss was actually low and the amount lost during the 2003 - 2009 period amounted to 243 metric gigatons per year. This mass loss was enough that it contributed .68 millimeters of sea rise per year. During that one, seven-year period, Greenland melt water raised the oceans by about 5 millimeters (about .2 inches) all by itself. Projections are that melt water from the GIS will add about 9 inches (22 centimeters) to the sea level by the year 2100. That figure does not include melt water from Antarctica and glaciers.

Meanwhile, another study has been released that also indicates the melt rate is not going in our favor. The second study has to do with the melt ponds on the surface of the ice. As the ice melts in the summer, not all of it can flow away and it forms lakes on top of the ice. Sometimes, these lakes will refreeze when winter returns. Sometimes, the ice will crack and the water can flow into the interior of the ice sheet in a matter of a few hours. Either way, melt ponds are not good. Ponds are darker than ice and absorb more sunlight than the bright ice. The more ponds you have, the more heat gets absorbed, leading to more melting. If the water flows into the interior then it transports that heat into regions that would otherwise be insulated. That heat then gets trapped inside instead of being able to radiate into space. One scenario leads to more melting. The second scenario leads to a lot more melting.

The study released some interesting data. The melt ponds normally do not form outside of a band along the edge of the ice sheet. Away from the coast, it remains cold enough through most summers to prevent melt ponds from forming. But, that melt pond band has grown by 35 miles (56 kilometers) since the 1970s and is expected to have doubled by the middle of this century. Meaning, the melt rate will accelerate.

This changing nature of the melt ponds has not been included in projections, so the authors of this study believe the projections are low and we can expect to see even larger amounts of ice melt than we previously thought we would.

All in all, the data is not looking good for anyone in low-lying coastal areas. That's only a few billion people.

Once again, tell me how global warming is good for us.

The Status of the Greenland Melt Season

Although it is located in the Arctic Region, the Greenland ice sheet (GIS) is much different than the Arctic sea ice. For one thing, it is on land and not in water. But, it is also much thicker. The average thickness of the GIS is about 7000 ft (1.4 miles) and about 10,000 ft (1.9 miles) at the thickest. It covers an area of over 660,000 square miles (2.5 times the size of Texas) and is the second largest ice sheet in the world, after only the Antarctica ice sheet. There is enough ice stored in this ice sheet to raise the world's ocean level by about 24 feet if it all melted.

Naturally, we are concerned with the conditions of the GIS. First, because it is a factor in the world's weather and most North Atlantic icebergs originate here, but because it is a indicator of how the climate is going. Unfortunately, we see one more indicator of global warming going on here.

We would expect to see melting and freezing in the ice sheet due to the seasons, and that is what we see. Some of the ice melts in the summer and then snow is deposited in the winter. In addition to that, we also see that the amount of melt in the summer is greater than the amount of deposit in the winter. Take a look at this graph here:

Source: Polar Portal

This shows the mass of the GIS over a period of more than ten years and we can see that the mass has a seasonal change, just as we expected. It increases in the winter and decreases in the summer. No controversy there. We can also see that the total mass has been declining for the entire period. Before 2004, the total mass was over 1000 gigatons (billion tons) above the long-term average. By 2014, this total mass had dropped to about 1800 gigatons below the average. That is a change of over 2800 billion tons of ice in about 10 years. Not good.

By the way, this occurred during the period when deniers have insisted there is no global warming. Once again, we see facts put the lie to their claims.

So, how are things going this year? Again, not good. Take a look here:

Source: NSIDC

This graph shows the percentage of the ice sheet that is melting at any given point of time compared to the long-term melt extent average (the dotted line). This shows us that the melt extent started out pretty close to average during the early part of the year. There was a spike in May, but that is not too alarming by itself. We expect to see the graph zig-zag back and forth as the weather changes. However, we are seeing much more than just a zig-zag starting with early June. The level of melt extent has shot up to the vicinity of 40%. That means about 40% of the ice sheet is melting right now. That percentage is already far in excess of the average maximum value which typically occurs in late July and reaches about 25%. 

And the forecast for additional melting? It is difficult to make a good forecast, but there is one thing that troubles me. Look at this plot.

Source: Polar Portal

This plot shows the albedo relative to the long-term average. Albedo is the measure of how well something reflects light. Something with an albedo of 1 (or 100) is a perfect reflector. An albedo of 0 means it reflects nothing at all - it would be perfectly black. Red areas on the above plot show where the current albedo is lower than the long-term average. Blue areas show where the current albedo is higher than the long-term average. The lower the albedo, the worse the surface reflects light and the more light it absorbs, leading to increased melting. Blue areas mean the albedo is higher and reflects light better, so melting would be reduced compared to the long-term average. The plot is not encouraging. There are some areas that are colored blue, but some shade of red dominates the plot area.

What could cause the lower albedo? There are two things that have been linked to this. One is soot from fires, the other is melt ponds. As we have more forest and wild fires due to climate change, the soot is carried on the winds and some of it is deposited on the GIS, lowering the albedo. Then, as the ice melts and forms ponds of water, the albedo drops even more because ice is a good reflector, but water is a good absorber.

Combining this data and the melting trend so far makes me think this will be a bad year for ice melt on Greenland. The summer of 2012 was the record bad year, hopefully we won't get that bad.