Two Seasons in One

Over the past few years, especially during the past two winters, weather conditions have been dramatically different in western and eastern regions of North America.  While California endured another warm, dry winter and southeastern Alaska received very little snow, the American Midwest was raked by frigid Canadian fronts and New England was buried by record-breaking snowfalls.

More than an inconvenience for humans and fodder for cable news programs, this stagnant weather pattern (an atmospheric ridge in the west and an atmospheric trough in the east) has caused significant ecological impacts.  A severe, four-year drought persists in the California, threatening water supplies and fueling massive wildfires.  Warm waters along the West Coast have diminished food supplies for many predators, altering their migrations and hunting patterns; stranded by parents who must feed well offshore, young sea lions have turned up on the beaches of California, exhausted, hypothermic and malnourished.  In the East, of course, the record snowpacks have set the stage for regional flooding and stream erosion.

While global warming is surely playing some role in altering the jet stream pattern, such stagnant weather patterns have occurred throughout the evolution of our Continent and will surely redevelop in the future.  Indeed, periods of drought and deluge have played a significant role in the dispersal and behavior of species throughout natural history, including the migration and settlement patterns of humans.