Friday, June 2, 2017

Lakes and climate change

Good article on a slightly-overlooked but very important aspect of climate change.  It's a long article, discussing several different phenomena, from Science News.

Lakes worldwide feel the heat from climate change

Here are three noteworthy excerpts.

1. "Globally, observations show that many lakes are heating up — but not all in the same way or with the same ecological consequences. In eastern Africa, Lake Tanganyika is warming relatively slowly, but its fish populations are plummeting, leaving people with less to eat. In the U.S. Upper Midwest, quicker-warming lakes are experiencing shifts in the relative abundance of fish species that support a billion-dollar-plus recreational industry. And at high global latitudes, cold lakes normally covered by ice in the winter are seeing less ice year after year — a change that could affect all parts of the food web, from algae to freshwater seals."
2. "Lake Superior is warming so quickly because it is stratifying earlier and earlier each year. It used to separate into its summer layers during mid- to late July, on average. But rising air temperatures mean that it is now stratifying about a month earlier — giving the shallow surface layers much more time to get toasty each summer. “If you hit that starting point in June, now you’ve got all summer to warm up that top layer,” Lenters says."
3. "Ecological changes put into motion during a particularly cold or hot time can send ripples during the following seasons, researchers are finding. “What happens in previous seasons sometimes matters more than the current season,” Lenters says. This is especially true for lakes at high latitudes that are covered in ice each winter but may see less ice as temperatures rise. Ice acts as an insulator, protecting the waters from big changes in the air temperature above. When the ice finally melts in spring, the water is exposed to warming from the atmosphere and from sunlight. “It’s a way the temperature can really rapidly increase in those lakes,” Hampton says."

No comments: