Global climate change has been a pretty hot topic in the world of meteorology and climatology for quite some time now. Skeptics and pro AGW (Anthropogenic — meaning human as opposed to natural — Global Warming) have raged on and on. One of the main components that people like to look at to track the degree of warming is the amount of Arctic Sea Ice loss. As the calendar slides through August and into September, we get closer and closer to the minimum ice extent for the year, before recovering for the fall and winter. Arctic Sea Ice has really declined in the past several years — potentially due to AGW, as the amount of loss last year was absolutely staggering. In fact, the entire 2007-2012 period saw unprecedentedly low levels of Arctic Sea Ice that led many to become quite worried about this being the new normal.
Most global climate simulations indicate that the area of greatest warming would be in the Arctic — mainly because it is easier to heat something that is cold than what is hot. Decreasing the amount of Arctic Sea Ice could lead to lots of devastating climate feedbacks on the Earth’s system, such as a lot less radiation being deflected back into space, and further yielding warming. This is because ice and snow have a higher albedo (ability to reflect heat radiation back into space) than water. Thus, a warming arctic –> more water and less ice & snow –> lower albedo in the arctic –> less heat radiation is reflected back into space (and is instead absorbed by the water) –> warming arctic. This means that the feedback helps to amplify the original effect of warming the arctic, without increasing the warming effect itself.
When the Artic regions are quite warm, this is obviously bad for many ecosystems alike. But it would also greatly alter the weather patterns in that it would change the jet stream configuration, since if you are warming the Arctic a lot more than the equatorial latitudes, you are decreasing the temperature gradient between the two, which is what fuels the jet stream to begin with. There are a lot more climate feedbacks and such, but to save time, we won’t get into that for now.
Arctic Sea Ice can be measured in two ways: ice extent and ice area. The National Snow and Ice Data Center explains the differences well here, but essentially, the analogy is swiss cheese. Extent would be the distance from the edges of the cheese and all of the space inside the edges — so it does not include the holes, whereas the area takes the holes into account. There are pros and cons to using each method, but the NSIDC uses extent.
The chart above shows the Arctic Sea Ice extent from the past several years, in comparison with the 1979-2006 averages. Obviously, we are still well below the 1979-2006 averages, so it is not time to “cancel” global warming. However, we have had a very significant recovery from this time last year — it is almost two million square kilometers above last year’s level! This is great news. Although we are really only near the 2009 level and not necessarily that deviant from the past several years, the increase is quite significant and a bit unprecedented, since year-to-year increases of this magnitude are rare.
Additionally, the NSIDC graph on the right shows that ice extent is now greater than it was in 2009 at this time — again, quite the feat considering how low 2012 was. Thus, the ice extent is actually the highest it has been since 2006. I’m not sure if we will finish above 2009 as far as the minimum extent is concerned (it will be close). But it certainly seems like we could finish above 2010, and remain over 5 million square kilometers during the ice’s minimum.
Potential Implications: It’s hard to completely quantify what this really means. But this is certainly good news — it would have been awful had years like 2007 and 2012 become the new normal. And it seems the doom and gloom regarding ice continuing to descend like the Tower of Terror was a bit unsubstantiated. There are a few ideas that we do have, however. It relates to the feedbacks.
One reason why many speculate that 2012 had such low ice concentration was due the positive (warming) feedback I mentioned earlier. It regards a warming pattern– thus, less ice — further leading to more warming, via creating an environment with a lower albedo. Some even went as far as to say that a negative (cooling) feedback could not have any effect on the ice concentration, given how overwhelming the positive feedbacks are, and how deep of a hole we have dug. Now, the positive feedbacks are pretty overwhelming, but that does not mean that a negative feedback that could help to increase ice extent do not have prevalence — especially if the prevailing weather pattern can undergo some changes that would help to favor more ice, and thus, the negative feedbacks.
If it is true that more ice loss can accelerate warming due to a positive feedback, which could thus help to decrease ice further (it goes on and on — that’s what a feedback is) then it must also be true that more ice gain can accelerate cooling, which would help to increase ice further. Consider this: Figure 1 shows that on July 22, we were actually very close to the 2012 levels of ice, and pretty far below 2009. However, 2012 nosedived after July 22 and especially in August, whereas 2013 really started to level off. It almost seems impossible to explain such recovery without a feedback. A favorable weather pattern for ice sets up, less ice melts, leading to a higher albedo, leading to more heat being reflected back into space. Thus, cooler temperatures, and further, less ice melting. Without this feedback, we probably still would have been above 2012 levels, but perhaps closer to 2008. These feedbacks prove that the weather does matter, and not every climate signal and AGW signal will override that.
What weather patterns lead to more ice and less ice? Some scholarly research papers show that it is related to an Arctic dipole pattern — a positive dipole will generally lead to less ice, and a negative dipole pattern will lead to more ice. A positive dipole essentially means you have a strong positive anomaly of some quantity overlayed with a strong negative anomaly of some quantity. With regards to weather, the quantity is usually pressure. A positive dipole pattern in the Arctic will lead to stronger winds, which helps to transport more sea ice from the Arctic towards Greenland and the Barents Seas, whereas a negative dipole decreases ice export, but the export that does occur goes from the Arctic towards the Bering Strait.
Increased export in itself leads to more melting, because ice being exported away from the Arctic will lead to it being dislodged into warmer waters. Another reason why warming ice is so dangerous is because the warmer the ice is, the thinner it becomes, making it easier to export. But what the positive dipole pattern also does is very important. The wind direction that exports ice from the Arctic to Greenland is the same wind direction that transports warmer, Pacific oriented waters from the Bering Sea into the Arctic. A negative dipole pattern prevents this, whereas a positive dipole pattern favors this.
A paper titled “Dipole Anomaly in the Winter Arctic Atmosphere and its Association with Sea Ice Motion” written by Bingyi Wu, Jia Wong, and John E. Walsh states the definitions of the Arctic dipoles. A positive dipole is when there are negative sea-level-pressure (SLP) anomalies between the Kara Sea and the Laptev Sea, with positive SLP anomalies from the Canadian Archipelago extending southeastward to Greenland (negative is the opposite).
The composite above shows the 2012 pattern. There were very low pressures between the Kara Sea and Laptev Sea — an indication of not only the positive dipole pattern itself, but also of strong storms which would help to further increase winds, and thus, transport more ice. There were also relatively high pressures in Greenland. The dates shown were from July 23 through August 25 — right when 2012 and 2013 started to diverge in ice extent.
The composite on the right shows the 2013 pattern from July 23 through August 25. As you can see, it’s almost the complete opposite of 2012, especially in the Kara Sea and Laptev Sea areas. Where the pressures were low, they are now high. Also, the Greenland area has seen lower pressures than in 2012, further proving the difference in the dipole pattern. This explains why 2013 has almost two million square kilometers more of ice extent than 2012. The fact that there has been a more favorable weather pattern for ice maintenance this year helps to yield a negative feedback reaction to maintain more ice.
This goes to show that the weather pattern does matter, and can overcome strong climatic signals for global warming. That being said, it’s not like we have recovered to pre-2006 levels yet. So one could argue that considering how favorable the weather pattern has been for ice maintenance, that we really should have even more ice than we do, which I think is somewhat valid.
Regardless, however, this year’s recovery is great news, and in my opinion, proves the validity of negative feedbacks in the Arctic. However, we are not nearly out of the woods, as the climate in the long haul is still warming. But hopefully, Arctic Sea Ice can keep recovering.