I’ll have to admit the biggest request for weather articles lately has been related to all of the rain that some regions have seen over the last few months. If you are one of those people waiting to see just how much rain fell and how it compares to past years, I’m afraid you will have to wait until the next issue, as I am still crunching some of the numbers. Instead, this week we are going to take a look at what is going on in the Arctic as we head into the peak melt season for Arctic sea ice.
Occasionally, over the last few years, I have written about Arctic sea ice and how we have seen a dramatic drop in not only the surface area of sea ice but also the total volume or amount of sea ice. If you don’t remember seeing those articles here is a brief summary of why this is such an important story.
Dur ing the summer, the high Arctic has sunlight falling on it 24 hours a day. When it falls on ice, some of the sun’s energy is used to melt the ice, but a good portion is reflected off of the ice back into space. This means energy is basically “lost” or no longer available to heat the Earth. If we melt or lose the ice cover on the Arctic Ocean, then more of the sun’s energy can be absorbed, since open water will reflect less of the sun’s energy. This additional energy is now added to the overall energy balance of the Earth. How this will affect our overall climate no one is sure, but if you add more energy or heat to one part of the planet without removing it in another area or at another time – well, I think you can figure out what will happen.
During the summer the Arctic will always see a drop in the amount of sea ice. This happens every year and has been going on for thousands of years, so what’s the big deal? The amount of ice disappearing is raising the alarm. Over the last 30 to 40 years (since reliable satellite records of Arctic ice have been available) the amount of ice during the summer has declined by a significant amount. At the start of this period sea ice coverage would drop from a winter high of around 15 million to 16 million square kilometres down to around 10 million to 11 million. Today we are seeing ice coverage drop from a winter maximum of between 14 million and 15 million sq. km down to around six million to seven million. That is a huge change in the amount of water now open to absorb the sun’s energy!
OK, lesson over. Now on to what is currently going on in the Arctic. Interestingly enough, there has not been a lot of news about what is currently happening in the Arctic. Earlier in the spring we saw a very slow start to the melt season and we actually saw ice amounts fairly close to average (at least within two standard deviations of average). Normally, the non-global- warming group would be all over this, but they were curiously quiet this year. The melt began to speed up in May, and really picked up speed in June. By the end of June, the amount of sea ice in the Arctic was at its second-lowest level (for June) since satellite records began. Since then, the speed of the melt has continued, and at present, the amount of sea ice is at the lowest extent ever measured for this time of year. Not only is the surface area declining rapidly, but the volume of ice is also at historic lows. Estimates from the University of Washington Polar Science Center has the volume of sea ice down a remarkable 47 per cent during June, compared
to the maximum measured back at the beginning of the satellite records.
So what is causing all of this melting? Once again this year, we see a weather pattern known as the Arctic Dipole dominating this region. Under this pattern we see a high-pressure system centred north of Alaska and a low-pressure system off the west coast of Siberia. The combined action of the air flow around the high and the low is pushing warm air into the Arctic. Interestingly, this weather pattern was virtually unheard of until the late 1990s and since then has become fairly common. Could it simply be a natural change in the Arctic weather pattern? Possibly, but more likely it is being driven by changes in global temperatures.
The question that remains for 2011 is whether we will continue to see the Arctic Dipole pattern continue – and if it does, will this then allow for yet another record-breaking drop in the amount of sea ice? Again, the answer is “Who knows?” But it certainly looks like we are heading toward an ice-free summer Arctic much sooner than most people think.
BytheendofJune,theamountofseaice intheArcticwasatitssecond-lowestlevel forJunesincesatelliterecordsbegan.