Tag Archives: Antarctic

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

Loss of Antarctic Ice Causing Gravity Dips

Loss of ice in Antarctica has been discussed extensively due to its implications for rising sea levels and the changing landscape of the continent, but it turns out that there is another unexpected effect: dips in gravity.

The ESA’s Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) satellite obtained high-resolution measurements of Antarctica’s gravitational field between November 2009 and June 2012. Recent analysis led by Johannes Bouman of the German Geodetic Research Institute found that where the ice has been receding, so has the gravity field. The paper has been published in the journal Geophysical Research Letters

In order to monitor the melting, draining, and regrowth of Antarctica’s ice more precisely, it has been divided up into catchment basins. GOCE is the first instrument sensitive enough to detect local changes in gravity specific to each individual basin. Additionally, GOCE’s data provides geologists with insights into earthquakes and volcanic activity.

GOCE’s measurements were combined with data from NASA’s Gravity Recovery and Climate Experiment (GRACE), an older satellite whose readings are more coarse. Together, they were able to generate an extremely accurate and detailed model of Earth’s gravity field, even exploring the differences between the upper mantle and crust of the planet, as well as determining the upper atmosphere’s density.

This is the 2011 GOCE geoid that represents variations in height. Copyright ESA/HPF/DLR

This gravity model can be incorporated with data collected from ESA’s CryoSat satellite, which is a radar altimeter used to record depth of Arctic and Antarctic ice, as well as variations in sea levels. This will allow scientists to have a better understanding of this ever-changing landscape. 

Due to the effects of climate change, Antarctica is losing ice mass at an unprecedented rate. Every year since 2009, the rate of ice melt has increased by a factor of three from the previous year. There has been a loss in ice volume of about 125 cubic kilometers (78 cubic miles) of ice each year for the last three years. This loss was well reflected within the GOCE/GRACE gravity model and could be used to predict losses in the future as well. 

“We are now working in an interdisciplinary team to extend the analysis of GOCE’s data to all of Antarctica,” Bouman said in a press release. “This will help us gain further comparison with results from CryoSat for an even more reliable picture of actual changes in ice mass.”

Read more: http://www.iflscience.com/environment/loss-antarctic-ice-causing-gravity-dips-0