Glaciers Sizzle as They Disappear Into Warmer Water

"Nov. 27, 2013 — Scientists have recorded and identified one of the most prominent sounds of a warming planet: the sizzle of glacier ice as it melts into the sea. The noise, caused by trapped air bubbles squirting out of the disappearing ice, could provide clues to the rate of glacier melt and help researchers better monitor the fast-changing polar environments." 

Erin Pettit, a geophysicist and researcher at the University of Alaska, would constantly hear popping and cracking sound when she would kayak in the northern waters. Underwater microphones that she had set up also picked up the sounds. She believed it to be the melting of ice but couldn’t confirm her theory. So she received help from Kevin Lee and Preston Wilson who are acoustic experts from the University of Texas. She sent them a chunk of glacier, which they mounted in a tank of chilled water. They recorded the audio and vide of the ice melting and matched the sounds of the recording to the escape of bubbles from the ice. Lee said that the bubbles make sound when they are being released by oscillating at a frequency between 1 – 3 kilohertz. He said that the smaller the bubble the higher the pitch would be.

Scientists have known for decades that bubbles form in glaciers when snow crystals trap air and then get squashed down under the weight of more snow. As more snow accumulates and compacts, it turns into ice and that air bubbles are pressurized. The bubbles form by even distribution within the ice. This is a way that can measure the rate of ice melting.

“Pettit and Lee say they could imagine using hydrophone recordings in glacial fjords to monitor relative changes in glacier melting in response to one-time weather events, seasonal changes, and long-term climate trends.” Sound travels a long distance underwater; therefore they are able to place microphones far underneath unstable sheets of ice to record sound. The audio recordings would complement other methods of measuring the rate of ice melting.

Sources:

http://www.sciencedaily.com/releases/2013/11/131127170103.htm

http://d1jrw5jterzxwu.cloudfront.net/sites/default/files/uploads/2012/06/Arctic-Ice-Alaska-web-size-97140096.jpg

http://blog.mixonline.com/briefingroom/wp-content/uploads/2012/02/Sound-Devices-and-Ambient-Recording-3.jpg

Volcano Discovered Smoldering Under a Kilometer of Ice in West Antarctica: Heat May Increase Rate of Ice Loss

"Nov. 17, 2013 — It wasn't what they were looking for but that only made the discovery all the more exciting."

In January 2010, a team of scientists set up a seismograph machine in West Antarctica. It was the first time scientists had placed instruments that would work year-round, even in the coldest parts of Antarctica. The machine measures disturbances created by earthquakes to make pictures of the ice and rock deep inside West Antarctica. The goal is to weigh the ice sheet and reconstruct Antarctica’s climate history. In order for them to do that, they would need to know how the mantle would react to a huge ice sheet. They needed to know whether the mantle was “hot and fluid or cool and viscous”. The seismic information will allow them to find out the properties of the mantle. Amanda Lough, a PhD student, found two seismic bursts in January 2010 and March 2011. She started to investigate the area. Eventually, it was found that there is a volcano forming a kilometer beneath Antarctica. “The discovery of the new as yet unnamed volcano is announced in the Nov. 17 advanced online issue of Nature Geoscience.”

At first, they didn’t know what was under Antarctica, but Lough noticed that what was under Antarctica resembled mountains. Soon, she realized that they were actually volcanoes. The seismic activities were low in frequency suggesting that they weren’t part of plate tectonics. They looked at airborne radar and observed that there’s elevation in bed topography in the same area where the seismic activities took place. They also showed a layer of ash buried under the ice. This layer was only found in the area where the volcano is located. The ash layer sets the age of the eruption at 8,000 years ago. They think that the ash might’ve come from Mount Waesche, but they don’t know when was the last time the volcano was active.

In Antarctica most mountains are not volcanoes, but that doesn't apply in West Antarctica. It's believe that there might be a hotspot under the volcano. It’s believed that the volcano will eventually erupt; they do not believe that the volcano will punch through a kilometer of ice, though. However, they do believe that it will melt a lot of ice, creating many lakes. This will increase the rate of ice-mass that is lost in West Antarctica.

Sources:

http://www.sciencedaily.com/releases/2013/11/131117155609.htm

http://upload.wikimedia.org/wikipedia/commons/9/93/Antarctica_major_geographical_features.jpg

http://en.wikipedia.org/wiki/File:MountSidleyWaescheMap.jpg

Expert Assessment: Ocean Acidification May Increase 170 Percent This Century

"Nov. 13, 2013 — In a major new international report, experts conclude that the acidity of the world's ocean may increase by around 170% by the end of the century bringing significant economic losses. People who rely on the ocean's ecosystem services -- often in developing countries -- are especially vulnerable."

A group of experts have agreed on their ‘levels of confidence’ about ocean acidification during the Third Symposium on the Ocean in a High CO₂ World in September 2012. The summary will be revealed in November 18, 2013. Experts agree that ocean acidification will affect marine life and subsequently lead to human consequences as well, specifically in economic losses because of a decline in shellfish.

Ulf Riebsel, one the lead coauthors of the summary, says that if we continue to emit CO2 the way that we do now, we must prepare for economic and ecosystemic losses. But, if the rate of CO2 gas were reduced, then this would slow acidification. An outcome that was emphasized was that the erosion of coral reefs could outpace the building of coral reefs this century. Another outcome is that coral reefs in the deep sea may become unsustainable. Wendy Broadgate mentions that there are many other consequences that the use of CO2 brings along. For example warming and deoxygenation are caused by a rise in CO2 emissions. She stresses that it is important to use less CO2 gas, but this will not make the ocean better; there are other problems such as overfishing.

There are three levels of confidence about the effects of ocean acidification, very high confidence, high confidence, and medium confidence. This is a summary from the article:

Very high confidence

• Ocean acidification is caused by carbon dioxide emissions from human activity to the atmosphere that end up in the ocean.

• The capacity of the ocean to act as a carbon sink decreases as it acidifies

• Reducing carbon dioxide emissions will slow the progress of ocean acidification.

• Anthropogenic ocean acidification is currently in progress and is measurable

• The legacy of historical fossil fuel emissions on ocean acidification will be felt for centuries.

High confidence

• If carbon dioxide emissions continue on the current trajectory, coral reef erosion is likely to outpace reef building some time this century.

• Cold-water coral communities are at risk and may be unsustainable.

• Molluscs (such as mussels, oysters and pteropods) are one of the groups most sensitive to ocean acidification.

• The varied responses of species to ocean acidification and other stressors are likely to lead to changes in marine ecosystems, but the extent of the impact is difficult to predict.

• Multiple stressors compound the effects of ocean acidification.

Medium confidence

• Negative socio-economic impacts on coral reefs are expected, but the scale of the costs is uncertain.

• Declines in shellfisheries will lead to economic losses, but the extent of the losses is uncertain.

• Ocean acidification may have some direct effects on fish behaviour and physiology.

• The shells of marine snails known as pteropods, an important link in the marine food web, are already dissolving.