The National Oceanic and Atmospheric Administration or NOAA recently released its annual update to the Arctic Report Card for 2011. This report updates conditions in the Arctic atmosphere, ocean and land mass, noting changes in marine ice cover and glacial melting among other issues. Scientists note that the Arctic acts as the world's "canary in a coal mine" because changes in climate in the Arctic are amplified compared to what is observed at lower latitudes where most of humanity lives. Now, let's take a look at NOAA's findings for 2011.
To open, it is well worth two minutes of your time to view NOAA's video on the Arctic Report Card for 2011:
Let's begin by looking at changes in the Arctic's sea ice. Over the past decade, sea ice distribution and thickness in the Arctic has changed. The Arctic sea ice is now both thinner and covers a less extensive area; this has resulted in both warming and freshening of the upper layer of the Arctic Ocean waters. In 2011, the summer extent of the sea ice cover dropped by 15 to 20 percent below the 20 year average between 1979 and 2000. In fact, the minimum Arctic sea ice extent in September 2011 was the second-lowest since satellite records began in 1979. Here are two maps showing the maximum and minimum sea ice extent for the months of March 2011 and September 2011 with the magenta line showing the median maximum and minimum ice coverage:
The March 2011 maximum ice coverage value was 14.64 million square kilometres; this is down 7.7 percent from the 1979 to 2000 average. The September 2011 minimum ice coverage value was 4.33 million square kilometres, the second lowest on record after 2007 and 31 percent lower than the 1979 to 2000 average. The five summers between 2007 and 2011 have seen five of the lowest ice coverage values and the 10 summers between 2002 and 2011 have seen nine of the ten lowest values. Here is a graph showing the gradual percentage decrease in both maximum and minimum ice extent values since 1979:
The biggest problem with the melting of sea ice is that it becomes a self-perpetuating machine. The increased melting is related to the concept of albedo. Albedo is a unitless quantity that indicates how well a given surface reflects light, with values varying between zero and one. Think of it as the whiteness of a surface. A black surface has an albedo of zero meaning that it absorbs all of the light energy that hits it and reflects none back. A white surface has an albedo closer to one meaning that it reflects more (or all) of the incoming light energy. There are two ways that we can relate to this concept; for those who live in northern climates, think about how bright it is on a sunny day when the ground is snow covered. Most of the sun's light is being reflected back and very little is being absorbed by the snow surface (otherwise, it would melt very quickly). In contrast, in warmer climates, all you need to remember is how hot a black asphalt surface gets when the sun hits it. The asphalt absorbs the sun's light energy and it heats up. Now let's go back to the ocean. The water in the ocean has an albedo of 0.07 meaning that it reflects back only about 6 percent of the sun's light energy and absorbs the remaining 94 percent which causes it to heat up. In contrast, sea ice without snow has an albedo of 0.5 to 0.7 meaning that it reflects 50 to 70 percent of the incoming light energy and generally absorbs less than half, meaning that it heats up relatively slowly. Sea ice covered with snow has an even higher albedo of 0.9; in this case, the snow actually acts as an insulating blanket for the underlying ice because it absorbs only 10 percent of the sun's light energy. However, once the snow on the ice begins to melt and form puddles, the albedo drops and the water begins to warm as it absorbs the incoming light because it has a lower albedo value. These shallow puddles have an albedo of 0.2 to 0.4 and can drop as low as 0.15 as the puddles enlarge. Here is another interesting video from an NOAA stationary camera showing the melting of sea ice and the formation of ponds on the ice surface in 2011; each few seconds of the clip is another day:
Notice how the ice retreats from the foreground? The melting would have progressed further into the months of August and September but the camera tipped over due to the melting ice. As the albedo increased, the melting rate increased.
Now, back to the NOAA report. Here are a series of maps showing the annual ice extent minimums for several sample years showing how much the area covered has declined since 1980 with the median ice extent area outlined in magenta:
The NOAA also notes that the age of the Arctic's sea ice has changed since record keeping began. In recent years, there has been greater loss of older (defined as older than four years), thicker and more resilient to melting ice (shown in white) as exhibited on these maps:
Note that the area covered by the oldest sea ice reached a minimum in 2011 when compared to the previous two years. I'd suggest that this does not bode particularly well for the future since the younger ice is much less resistant to melting.
Now, let's take a brief look at the changes in water temperature in the Arctic. The summer of 2011 saw water temperatures over much of the Arctic Ocean rise well above the mean values experienced between 1982 and 2006. Warmer temperatures (0.5 to 3.0 degrees Celcius) were noted in the area north of Alaska and Canada and even warmer temperatures (up to 4 and 5 degrees Celcius) were noted north of western RUssia and Europe as shown on these maps:
The sea surface temperatures (SST) in 2011, although above the long-term mean, are still below the highly anomalous temperatures seen in 2007. Unfortunately, solar radiation penetrates more easily into the upper ocean as the ice cover thins, resulting in higher water temperatures, both at the surface and at depth. In the area to the north of Canada, warmer water temperatures have descended to depths of around 30 metres.
As melting increases, the chemistry of the ocean's water changes as well. The water salinity decreases and becomes fresher as melting of both sea ice and nearby glaciers occurs. The volume of fresh water in parts of the Beaufort Sea have increased by 25 percent compared to the 1970s. Not only has the volume of fresh water increased, there has been a change in the chemistry of the Arctic ocean water as well. The open waters of the Arctic Ocean can take up increasing volumes of carbon dioxide resulting in more acidic ocean water than would be the case if the water was ice-covered. This is problematic for organisms that form their shells from various forms of calcium carbonate (i.e. calcite and aragonite) as the level of calcium carbonate in the water is suppressed and the water becomes increasingly corrosive. Ultimately, these changes will work their way through the food chain, impacting the survivability of some organisms leading to additional stress in the Arctic ecosystem.
I realize that climate change naysayers will refute the conclusions that follow these observations but I think that it is important that we use the multi-year observations of NOAA's scientists as another series of data points that will ultimately lead to mankind doing what is right for the environment and putting the world's ecosystem ahead of corporate profitability and political gain. There is no doubt, the Arctic ecosystem is changing; whether it is permanent or not, only time will tell. Let's hope that it's not too late before the finger pointing stops and governments act to preserve this world for future generations.