With beautiful fall weather firmly in place across pretty much all of Western Canada, the question for me is, exactly what should I discuss in this week s weather article? We ve already discussed just what Indian summer is, we have taken a look back at the summer of 2011, and we ve looked ahead to see what the fall might have in store for us. So I think for this week we ll take a look at a number of smaller weather stories that could eventually have an impact on our weather.
First of all, I do have to revisit the current Indian summer weather. Everything came together pretty much as anticipated late last week. A strong ridge of high pressure built over the western Prairies and it brought plenty of sunshine along with warm to hot temperatures. While Manitoba has not officially broken any temperature records as of Sept. 25, a number of stations in Saskatchewan and Alberta did. This is due to a large upper low that stalled out over the Great Lakes. This is the same low that brought rain and cool conditions to a large portion of Manitoba early last week. This low acted as a block to prevent the western ridge from pushing east. This meant the warmest conditions stayed to our west for the most part (far western Manitoba did see some really warm conditions last Saturday). Overall, I don t think anyone was complaining about this weather!
If we go north now and take a look at what s going on in the Arctic, we ll find that the 2011 melt season has come to an end and that the amount of Arctic sea ice has begun to increase. This summer the amount of ice cover in the Arctic was at the second lowest ever recorded since satellite records began in 1979. At its lowest this year, the amount of ice fell to 4.33 million square kilo-metres, just short of the record of 4.17 million square km set in 2007. This ice loss is a remarkable 35 per cent below the 1979-2000 average summer ice cover. Both the Northwest and Northeast passages were open for ship navigation this year; this marks the fourth year in a row this has happened and, remarkably, the fourth time this has ever been recorded, with fairly accurate records going back to 1497. What s
interesting is that the 2007 record-low ice coverage occurred during a year that saw very unusual weather over the Arctic, with plenty of sunshine and warm temperatures. This year the weather was pretty much average across much of the Arctic and we still saw near-record-low amounts of ice coverage.
While the amount of ice coverage in the Arctic did not reach a record low this year, the volume of ice did. As more and more ice melts each summer, the amount of thick multi-year ice is declining, resulting in a reduction in ice volume. Climate models now show that if this trend continues, the Arctic will become ice free during the summer by 2030 and we will likely see the North Pole ice free by 2020 or earlier. Other interesting
research is trying to determine the last time the Arctic was open for navigation. Some research suggests that between AD 1000 and 1300, there may have been several years when this occurred, but a more likely period was about 6,000 to 8,500 years ago. So what we currently see happening in the Arctic is truly unique in the annals of human history.
Now let s travel to our west, out over the Pacific Ocean. It appears La Nia is rebuilding as ocean surface temperatures across the El Nio/La Nia region drop to below average temperatures. The U.S. National Oceanic and Atmospheric Administration (NOAA) states several of the El Nio Southern Oscillation (ENSO) models predict an increase in the intensity of La Nia as we move into fall, and there is a fairly good chance it will last well into winter. They also point out that several of the models show neutral conditions across the Pacific this winter, so we ll have to watch this unfold over the next several weeks to months to see what happens. Whenever there is a fairly strong El Nio or La Nia episode, we see unusual weather conditions around the world. For our part of the world, La Nia is usually associated with colder-than-average winter temperatures. There was a fairly strong La Nia last winter and our region saw a warm start to winter followed by a cold end. I ll keep an eye on this current La Nia episode and follow up with more information in the weeks ahead.
Climatemodelsnowshowthatifthis trendcontinues,theArcticwillbecome icefreeduringthesummerby2030.