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 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.