Tag Archives: warming

Deep Ancient Water Is Stopping The Antarctic Ocean From Warming

The waters around the Antarctic may be one of the last places on Earth to feel the effects of man-made climate change. According to researchers at the University of Washington (UW) and the Massachusetts Institute of Technology (MIT), ancient seawater upwelling from the depths explainwhy the sea surface has remained roughly the same temperature while most of the planet has experienced temperature rises.

Using a combination of observations from floating ocean current trackers and cutting-edge computer simulations, the new Nature Geoscience study shows that this centuries-old seawater hasnt been to the surface since the dawn of the Industrial Revolution. Although the cooler waters around the Antarctic were previously blamed on ocean currents drawing sea surface heat down to the depths, it appears that cold water yet to experience the newly-warmed atmosphere is currently rising up to the surface.

With rising carbon dioxide you would expect more warming at both poles, but we only see it at one of the poles, so something else must be going on, the studys lead author Kyle Armour, a UW assistant professor of oceanography and of atmospheric sciences, said in a statement. We show that it’s for really simple reasons, andocean currentsare the hero here.

Observed warming over the past 50 years, as measured in degrees Celsius per decade. Its clear that the Southern Ocean has warmed by only a fraction, and it appears ocean currents are to blame for this unusual refrigeration mechanism. Kyle Armour/UW

Seawater from the deepest depths of the worlds oceans upwell at different times, and they do so when they become less dense than the water above them. This can happen for many reasons, including a reduction in salt concentrationor an influx of heat at depth, both of which make them more buoyant. On occasion, there can be a mechanical driver of seawater upwelling, such as persistent winds.

This is whats happening in the Southern Ocean, where extremely powerful westerly winds keep pushing warming surface water northwards; this gives the deeper, older water space to upwell into. The novel aspect of the waters here is that they have to upwell from depths of several thousand meters, far beyond the depths that most other oceanic currents reach. This means that it takes them an incredibly long time to reach the surface and interact with the atmosphere.

According to the models run by the team, the water only just beginning to reach the surface off the coast of Antarctica last experienced the Earths atmosphere centuries ago in the North Atlantic, before any serious man-made climate change had the chance to significantly heat it up. In fact, their simulations show that the oceanic currents that have experienced the most warming appear to be gathering at the North Pole, which also partly explains why Arctic sea ice is disintegrating so rapidly.

When we hear the term ‘global warming,’ we think of warming everywhere at the same rate, Armour added. We are moving away from this idea and more toward the idea of regional patterns of warming, which are strongly shaped by ocean currents.

The fact that Antarctic sea ice has been growing just as the Arctics has been disintegrating has baffled scientists for some time; irritatingly, this discrepancy is often cited by climate change deniers as proof that climatologists dont know what theyre talking about. It was only a matter of time before several explanations emerged, and this new study represents one of two corroborating theories helping to explain why the sea ice around Antarctica has been unexpectedly growing.

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Read more: http://www.iflscience.com/environment/deep-ancient-water-stopping-antarctic-ocean-warming

Snowshoe Hare’s Camouflage Thwarted By Climate Change

The forest-dwelling snowshoe hare (Lepus americanus)has the remarkable ability to change the color of its fur from brown in summer to white in winter in order to camouflage itself. However, as a new study in the journal Ecology Letters reveals, human activity is causing a snowfall reduction, leaving the wintry white hares standing out to predators like light bulbs, and increasing their mortality rate.

A recent study has suggested that two-thirds of all recent dangerous climatic events are directly attributable to human-produced (anthropogenic) greenhouse gas emissions. These impacts include the rapid alteration of ecosystems, including the types of forests inhabited by the snowshoe hare.

As the new study outlines, the snowshoe hare is remarkably well adapted to its North American environment. It is herbivorous in summer, but when resources are scarce in the winter, it is known to opportunistically become carnivorous to satiate its hunger. A nocturnal animal, it has specialized feet that prevent it from sinking into the winter snow and that protect it from very low temperatures.

A major predator of the hare is the lynx, a fast hunter over twice the size of the average domestic cat. Fortunately, the snowshoe hare has a clever defense mechanism: It is able to change its fur to white to match the color of the snowfall in winter, and brown to match the earthy ground in summer. These changes take about 10 weeks to completely occur, and are related to the production of melanin, a pigment, in its body. The more melanin in the fur, the darker it will be.

The summer morph of the snowshoe hair. Walter Siegmund/Wikimedia Commons; CC BY-SA 3.0

The rabbits detect the changes in the seasonal light through specialized retina cells, which let the brain know when to alter the production of melanin to match the fur coat color to the season. However, previous research has recognized that a decrease in snow due to increasing global temperatures has caused a mismatch between when the white fur appears and the start of a snowy winter.

In order to investigate if this causes an increase in mortality rate, the researchers of this new study tagged 186 snowshoe hares with radio collars in two large swaths of hare territory in Western Montana. These hares were monitored once a week for several years, particularly during the seasonal transitions from summer to winter.

As the light levels remained the same as global temperatures rose, the hares do indeed change their fur color too early for the increasinglydelayed snowfall; consequently, as the radio collars showed, their survival rate has been dropping for some time. In fact, their weekly survival rate suffers a 7 percent drop when snow arrives late or leaves too early.

This paper shows that the mismatch costs are severe enough to cause hare populations to steeply decline in the future unless they can adapt to the change, said Marketa Zimova, lead author of the study, in a statement.

Only time will tell whether or not individuals are able to change their fur color at slightly different times to adapt to the changing snow, and if they can survive long enough to pass on this ability to their offspring. Either way, the evolutionary clock for the snowshoe hare is ticking.

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Read more: http://www.iflscience.com/plants-and-animals/snowshoe-hares-camouflage-being-thwarted-climate-change