Tag Archives: sea ice

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

Wreckage Of Sunken Whaling Ships Discovered Off Alaskan Coast

The sunken remains of two ill-fated whaling ships have been found off the coast of Alaska, 144 years after they became crushed by pack ice, forcing all crew members to abandon their vessels. Though all were later rescued, the event marks one of the greatest catastrophes in the history of U.S whaling, and resulted in the loss of an entire fleet of 33 ships.

Back in the 18th and 19th centuries, whale oil was used around the world for heating, candle wax, soap, and a number of other purposes. As such, whaling was pretty big business, and attracted fleets from across the world to the Arctic each summer, when the ice relented and several species of whales migrated northwards.

However, the conditions at the top of the world can be unpredictable, as this particular fleet discovered to their peril in September 1871, when their ships became trapped in ice before they had a chance to manoeuvre away. Since the disaster, various artefacts from the sunken vessels have been discovered floating in the sea or washed up on the shore. Andresearchers have now located two of the ships for the first time.

Using sonar and other submarine-sensing equipment, a team of archaeologists from the National Oceanic and Atmospheric Association (NOAA) surveyed the waters along a 48-kilometer (30-mile) stretch of coastline near Wainwright, Alaska. In doing so, they were able to plot the outline of two flattened hulls, along with other items such as anchors, ballast and blubber-boiling equipment.

The researchers found anchors, rigging equipment, and other structural features of the sunken ships. NOAA

Until now, attempts to uncover the downed fleet had been thwarted by the thick layer of pack ice that covers much of the Arctic for large periods of the year, although a steady decrease in the amount of ice present during the height of summer over the past four decades has opened up new opportunities for conducting the search. As a consequence, the team was finally able to locate the ships last September, when the Arctic sea ice reaches its yearly minimum.

Reacting to the exciting discovery, project co-director Bad Barr said in a statement: This exploration provides an opportunity to write the last chapter of this important story of American maritime heritage and also bear witness to some of the impacts of a warming climate on the regions environmental and cultural landscape, including diminishing sea ice and melting permafrost.

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Read more: http://www.iflscience.com/editors-blog/wreckage-sunken-whaling-ships-discovered-alaskan-coast

Watch a 20-Mile Long Iceberg Drift Into the Southern Ocean

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A close-up of the rift that opened up across the Pine Island Glacier in 2011.
Image: NASA

Ever since a massive crack was discovered in Antarctica’s Pine Island Glacier in 2011, NASA researchers and other scientists have kept a close watch on this area. The crack cleaved off an iceberg, now known as “Ice Island B31,” which broke off from the glacier in November 2013, and has since been drifting across Pine Island Bay, a basin of the Amundsen Sea, toward the Southern Ocean.

According to the NASA’s Earth Observatory, the ice island “will likely be swept up soon in the swift currents of the Southern Ocean…”

During the five-month-long Antarctic spring and summer, an instrument called the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra and Aqua satellites captured a series of images showing the movement if the ice island. NASA recently released a time-lapse video of these images, showing the journey of this massive chunk of ice:

The ice island is much larger than your ordinary iceberg. Earlier this month, the U.S. National Ice Center, which tracks icebergs in order to alert ships of their presence, reported that B31 was 20.5 miles long and 12.4 miles wide. Scientists estimated its thickness to be about 1,640 feet thick.

While such a massive ice island breaking off from an Antarctic ice sheet might seem like a sign of a coming global warming apocalypse, scientists aren’t yet sure how significant this event is. “Iceberg calving is a very normal process,” said Kelly Brunt, a glaciologist at NASA’s Goddard Space Flight Center, in a NASA news story.

However, the crack that created this iceberg was well inland from the calving front of the Pine Island Glacier, which could indicate a new, more rapid era of ice melt. This would be ominous news, considering that the melting of land-based ice sheets, such as Antarctica and Greenland, already constitutes the largest contributor to global sea level rise.

NASA Iceberg

A NASA satellite photograph showing the ice island, B31, drifting toward the Southern Ocean as of March 2014.

Studies have shown that the Pine Island Glacier, in particular, has been flowing into the sea much faster than it used to. A study published in March, for example, showed that the West Antarctic ice sheet, which the Pine Island Glacier is a part of, have been shedding ice at an accelerating rate, with six large glaciers in this region discharging nearly the same amount of ice as the entire Greenland ice sheet.

The study examined glaciers in the Amundsen Sea Embayment of West Antarctica, which includes the Pine Island Glacier as well as the
Thwaites, Haynes, Smith, Pope and Kohler glaciers, each of which are behemoths in their own right.

In that study, a research team from the University of California at Irvine and NASA found that the total amount of ice coming off these glaciers has increased by 77 percent since 1973, with much of that increase coming since 2000. Together, these glaciers drain one-third of the West Antarctic Ice Sheet, or about 158 million square miles of ice, the study said.

The study also found, for the first time, that West Antarctic glaciers are not only flowing faster at the point where their base meets the ocean, which is known as the grounding line. Additionally, areas as far inland as nearly 160 miles are also speeding up their march to the sea.

Video showing melting process of the Pine Island Glacier, from the European Space Agency.

In the same way that plaque slowly rots a tooth until it falls out, mild ocean temperatures are thought to be causing ice to thin and retreat at the grounding line, where these glaciers meet the sea. This is likely setting in motion a chain of events that results in a far more unstable glacier.

Illustrating the high stakes involved in the fate of West Antarctica, the study found that these six glaciers contributed about 10% of all the global average sea level rise that occurred between 2005 and 2010. If all six glaciers were to melt completely (which is not expected to happen during this century), global average sea level would rise by a catastrophic 3.9 feet, the study said.

As Discover Magazine reported, if the entire West Antarctic Ice Sheet were to melt, sea level would rise by 10 feet or more. This would affect more than 100 million people, the magazine said on its http://blogs.discovermagazine.com/imageo/#.U1p88OZdXOc>ImaGeo blog.

Read more: http://mashable.com/2014/04/25/an-iceberg-6-times-the-size-of-manhattan-is-drifting-into-southern-ocean/