Part of the problem with melting ice, argues the first study, is that it’s mostly freshwater. Don’t get me wrong, I love freshwater — can’t get enough of the stuff — but cold freshwater doesn’t sink the same way cold saltwater does (because it’s not as dense). And part of what helps the currents do their job is the fact that cold water tends to sink. Any disruptions in temperature and salinity are likely to toy with that system in a severely objectionable manner. The Washington Post reports:
“Previous studies have generally had to estimate the amount of melting and then insert the meltwater into the ocean simulation by hand, or haven’t included the feedback between ice sheet melting and ocean salinity at all,” lead scientist Paul Gierz said.
The team’s computer models projected a drop in ocean salinity of about 7 percent in the areas near Greenland’s melting ice sheets, a decline that would alter deep-ocean circulation patterns over time, resulting in “less heat being transported to the high latitudes … which has implications for both North American as well as European weather and climate,” Gierz said.
Because the climate systems tend to respond slowly to environmental changes, the full impacts may not be felt for decades.
But we don’t have to wait for those impacts to kick in to get a feel for them: Another study suggests that there might be a gloomy historical case study for these kinds of ocean circulation changes. By examining ice core records and cave formations like stalagmites, researchers were able to salvage proxy temperature data from upwards of 12,000 years ago. Near the end of the last ice age, the authors write, rising temperatures led to rising sea levels and an influx of freshwater — the same kind of influx that today’s changing climate is expected to produce.
And the result wasn’t pretty: Changes in ocean circulation helped lead, for example, to an 18-degree Fahrenheit drop in Greenland over a period of less than ten years. Some of these changes “lingered for centuries,” writes The Washington Post. We’re talking 1,000-year droughts in the South Pacific.
A modest proposal, then: Start bottling that melting ice water and send it south. They’re going to need it in Vanuatu when the drought strikes. That is, of course, if the island isn’t first swallowed by the sea.
New studies deepen concerns about a climate-change ‘wild card’, The Washington Post.