Breathless weather commentators advise of the impending arrival of yet another polar vortex. Is it just me, or do weather events that we took in our stride in previous generations, now warrant weather warnings, special weather statements and advisories? (They may be an easy target, but I blame the lawyers, concerned about the liability of the forecasters if folks dare to venture outside without taking adequate precautions.)
So just what is a polar vortex? The polar vortex is an upper-level low-pressure field of air which rotates around the North (and South) Pole. The term ‘vortex’ refers to the counter-clockwise flow of air that helps keep the colder air near the Poles. The polar vortex acts as a barrier to isolate arctic air from warmer air to the south. It weakens in summer and strengthens in winter. However, variations in the strength of the polar vortex can cause disruptions in expected weather patterns across the northern hemisphere. This can be experienced as both masses of cold arctic air pushed southward, as well as masses of warm equatorial air pushed northward.
This is not something new. The term ‘polar vortex’ has only recently been popularized, bringing attention to a weather feature that has always been present. Many times during winter in the northern hemisphere, the polar vortex will expand, sending cold air southward with the jet stream.
However we appear to be seeing new phenomena. Recently Europe experienced colder temperatures than the Arctic as the polar vortex continues to collapse. We are experiencing melting events many thought was decades away.
The variability seen in the polar vortex has been linked to both unusually cold weather in eastern North America as well as unusually warm weather in the North Pole. What’s concerning is the frequency and duration of breakdowns in the polar vortex, indicating its potential collapse. While the strength of the polar vortex relies on the temperature difference between the mid-latitudes and the Arctic we concurrently see increasing average temperatures in the pole. In addition, NASA puts the rate of declining Arctic sea ice at 13.9 per cent per decade. These signs point to a continued weakening of the polar vortex and a potential collapse.
What appears to be happening is a global shift in the redistribution of heat from the mid-latitudes to the Arctic.
(Much of the information in the preceding paragraphs has been adapted from an article by Trevor Nave in Forbes dated February 27, 2018)
So as it turns out, there is much cause for concern. Not so much for what tomorrow’s weather will be, but that some of these major shifts in weather patterns may well affect our agriculture and our ability to feed ourselves.
Getting back to our local gardening outlook, it appears that we are locked into below-average temperatures for at least a week (I tend to view weather forecasts more than four days out as sheer speculation!). I have yet to find a spot in my gardens where outdoor planting is possible, but I was very heartened by a conversation with a Pakenham gardener who has a protected micro-climate where she was able to plant parsnip, radishes and spinach on the weekend.
And as I have pointed out, (perhaps to the point of tedium), there are many common vegetables that are incredibly cold hardy. Returning to the Hoop House garden I was very pleased to see that many of the vegetables planted early in March are growing very well thank you. The Hoop House interior temperature rises quickly to 20 C or higher on a sunny day but drops down to outside temperatures overnight. I’m sure that I don’t have to remind you that over the last month we have had at least 5 nights where the temperature dropped below -10 C.
Once these seedlings germinate they are incredibly tough. The following photos show seedlings of carrots, peas, radishes and spinach taken on Sunday,