By Anna Alvarado | UTS Staff Writer | SQ Online (2013-14)
Amidst current climate change discussions, NASA released a particularly alarming article regarding the Western Antarctic ice sheet. It stated that recent findings from two separate researchers from both the University of California, Irvine and NASA concluded that the rapidly melting ice sheet is unstoppable and irreversible. According to geologist Eric Rignot the event “has passed a point of no return”, which could heavily impact the rise of sea level rise in decades to come. In order to have a greater understanding of this event, we asked Dr. Helen Amanda Fricker from the Scripps Institution of Oceanography about the current state of Antarctica and its future implications. Dr. Fricker is an expert on ice and climate with research focusing on Antarctic ice shelf evolution and mass loss processes. She was able to provide a crash course lesson on what exactly is happening in the Western Antarctic ice sheet.
Essentially the West Antarctic ice sheet sits on top of a rock located many kilometers beneath the sea level. At some point, a portion of the ice sheet loses contact with the ground leaving a free floating ice shelf. This point is called the grounding line and is often about 1-2 kilometers deep below sea level. The reason why the ice sheet is melting rapidly is because warm waters are reaching underneath the ice shelf around the grounding line, pushing it backwards (see Fig. 1). These warmer waters are blown from more temperate climates up to Antarctica. “There’s been a lot of ocean heat delivered underneath the ice shelf,” Fricker said. “The winds in Antarctica are getting stronger as a result of the ozone problem. Westerly winds that are basically sitting just off the continental shelf around warmer waters are actually blowing that water.”
What is even more threatening than the increased amount of warm waters reaching Antarctica is the depth of the recessed grounding line underneath the ocean. As you go deeper down the ocean, the hydrostatic pressure increases causing the melting point of ice under water to decrease. “The deep part of the grounding line contains higher amounts of pressure, with every 10 meters of depth in the ocean adding on to the atmospheric pressure,” Fricker said. “So by the time you reach 1-2 km you’re at really high pressure and the melting point of ice is depressed. So water that is actually not that warm is actually warm enough to melt the ice.” This means that even slight changes in water temperatures can make significant impact in the rate and amount of ice melting.
The downward slope of the bedrock on which the grounding line retreats on also contributes to the larger amount of ice exposed to the warm water underneath the ocean surface. With melting ice comes an increased elevation of water due to a retreating grounding line, exposing larger columns of ice to warm water temperatures. “The thickness of the ice that’s crossing the grounding line is actually increasing because the elevation is higher,” Fricker said, “so the actual column of ice that’s crossing that grounding line is thicker.” This creates a feedback loop: warm water leads to ice melting causing grounding line retreat which exposes larger ice columns to warm water leading to more melting and so on. A combination of all of these factors is the reason why this instability is occurring in the Western Antarctic ice sheet and why it could not be reversed.
This idea of marine ice sheet instability is not new. It was first postulated by Dr. John Mercer in 1978, predicting that the increase depletion of the ozone layer will cause the warming of ocean waters and thus impacting Antarctica. The recent press release by NASA introduced two different researchers that proved the theory and brought true empirical evidence to the phenomena with the help of new and improved satellite technology and other methods of measurements. Researchers believe that this melting ice sheet will cause a sea-level rise in the order of 12 feet. To put such figure in perspective, this rise could engulf about half of the San Diego Convention Center and almost all of Coronado Island.
We as humans and as University of California, San Diego students are now faced with this irreversible phenomena that is undeniably caused by human impact on the environment. It is important to note that the changes brought upon by the melting ice sheet will not occur in the near future. However, these slight changes year to year can accumulate and intensify the effects of climate change. Several researchers have proven that human pollution, deforestation, overpopulation etc. have impacted climate change in significant ways and what is happening in Western Antarctica is an example of what these actions actually do. It is important to keep UCSD students aware of their own impact on the environment around them because what we do now will dictate the world of our future. Great ways to be more proactive about climate change is to be mindful of daily activities, make certain lifestyle changes that could reduce your carbon footprint and to educate yourself on what is going on in the nature around you. An excellent way to start learning is to take classes like Dr. Fricker’s class SIO 115: Ice and the Climate System which will be taught in this upcoming school year.