For the Northwest Territory of Canada, the story this summer has been one of record-setting wildfires. Fires casting away smoke plumes the size of thunderstorms, fires that burn regions of tundra the size of small states. Fires that just burn and burn and burn for weeks on end.
But to the south and east in Saskatchewan and Manitoba, the story is drastically different. For over the past month, unprecedented flooding in this region has wrecked untold damage to Canada’s farmlands.
(Powerful storms over Manitoba and Saskatchewan on July 23rd, 2014. Image source: LANCE-MODIS)
This situation is the result of an odd and wreckage-inducing tangle in the Jet Stream. For hot air has been funneling up over the Northwest Territory for the better part of two months now, pushing temperatures in this Arctic region into an unprecedented range topping the 70s, 80s, and even 90s on some days. This high amplitude ridge in the Jet Stream has been reinforced and locked in place, a result some scientists attribute to the loss of Arctic sea ice during recent years, setting up a hot weather pattern favorable to wildfires.
As the massive Arctic wildfires ignited and burned, they cast off giant streams of smoke, burdening the down-wind atmosphere with aerosol particles — an abundance of condensation nuclei for cloud formation. These smoke streams fell into a trough flowing down over Manitoba and Saskatchewan. The deep trough, often extending far into the Central US formed a kind of trap for storms and, like the fixed ridge over the Northwest Territory, it has remained in place for months on end.
Given this mangled positioning of atmospheric heat and moisture flows, it was only a matter of time before massive rainstorms erupted in the wake of the large-scale Canadian fires. And the result was an unprecedented flooding. The offspring of an unprecedentedly powerful and persistent atmospheric pattern set off by human warming.
Major Floods Wreck Canadian Crops
For some local farmers, the past couple of days have seen 48 hour rain totals in excess of 10 inches. A 100 year rain event at a scale few farmers in the region have ever seen. And the recent floods are just the latest in a series of heavy rainfalls that have been ongoing ever since early July. Flood follows flood follows flood. A progression that has left most farms swimming in inches to feet of water and mud.
In total, farmland encompassing 3 million acres in Saskatchewan and 2.5 million acres in Manitoba are now under water and are unlikely to produce any crops this year. As a result, wheat plantings are expected to decline by 9.8 percent from last year, canola is expected to decline by 5.8 percent from the June forecast, and oat is expected to decline by 6 percent, according to estimates from Bloomberg.
July flooding in these regions has so far resulted in over 1 billion dollars in damages to farmers. As much as half of these losses may not be covered as insurers are still reeling from severe moisture damages during 2011, just two years ago. As a result of the ongoing parade of storm casualties, insurers have also raised deductibles, leaving farmers more vulnerable to the odd and powerful new weather coming down the pipe.
The Part Played By Climate Change and a Mangled Jet Stream
We often hear of the expanding droughts of human-caused climate change wrecking croplands. But the upshot of expanding drought in one region is record downpours in another. And downpours, if they are intense enough, can have a negative impact on crops as well.
The cause of this is as simple as warming’s enhanced ability to evaporate water. For it is estimated by climate scientists that each degree C in temperature increase amplifies the global hydrological cycle by 7-8 percent. That means that current warming of about 0.8 C since the 1880s has resulted in about a 6% increase in both evaporation and precipitation. At the level of weather, this translates into more intense droughts under dry, hot weather, and more intense rainfall events under wetter, cooler weather.
(High amplitude Jet Stream wave pattern fueling wildfires in the Northwest Territory and record floods in Manitoba and Saskatchewan. Note the extreme northward projection of the Jet over the Northwest Territory and the strong, deep, trough back-flowing from Hudson Bay into Manitoba, Saskatchewan and the northern tier of the Central US. Image source: University of Maine.)
One mechanism that has tended to amplify drought and rain events during recent years has been a weakening and intensifying waviness of the Northern Hemisphere Jet Stream. This weakening has been attributed by some scientists to a large-scale recession of Arctic snow cover and sea ice. For since 2007, not one day has seen an average sea ice extent and the range has typically fallen into a zone between 20-50 percent below levels seen during the 1970s and 1980s. New major record low years in 2007 and 2012 have also fueled speculation that sea ice may completely melt away during one summer between now and 2030, 2025, or even 2020 — 50-100 years ahead of model predictions.
As the sea ice serves as a haven for cold air masses, its loss is bound to impact the resiliency of these systems and since a solid pool of cold air to the north is a major driver of Northern Hemisphere upper air currents, the weakening of this cold pool has had dramatic impacts on climates.
(Extreme dipole hot/cold pattern associated with Jet Stream mangled by climate change. Image is for July 14, a match to the above Jet Stream shot. Note the extreme heat in the ridge and the much cooler air in the trough. This is exactly the kind of pattern we would associate with sea ice retreat and Jet Stream weakening. Image source: University of Maine)
For this year, the ridge over Canada’s Northwest territory was a direct upshot in a northward retreat of the Jet Stream over Canada and, at times, into the Arctic Ocean. This set the stage for severe wildfires in the zone of warmth underneath this ridge pattern. To the east, a powerful downsloping trough pulled cooler air into Saskatchewan and Manitoba as well as over the Central and Eastern US. This set the pattern up for cooler than average conditions as well as for strong rainstorms.
The crop-shattering events of July were a direct result of this climate change induced ‘Song of Flood and Fire.’ A pattern we’ve seen repeat again and again over the past few years and one that may well intensify as both time and human-caused warming advance.
Hat-tip to Colorado Bob