What the ice reveals about Antarctica
The continent you’ll explore during your Antarctica cruise is not just an ice-covered island with penguins, whales, and seals. Under the thick ice are hidden freshwater lakes that contain thousands of microbes that hint towards a diverse array of life. In 2013, a team of researchers obtained the first uncontaminated water sample ever retrieved directly from an Antarctica lake.
Lake Whillans is a lake that lies below 800 metres of ice, 640 kilometres from the South Pole. The lake is only 2 metres deep and nearly 60 square kilometres in area. Because the lake is pristine, the team spent six years devising a way of removing the sample without contaminating the water from either the drilling equipment or by introducing invasive organisms into the lake. To avoid this, the team used ultraviolet radiation, water filtration and hydrogen peroxide to sterilize the machinery and the water used to bore through the ice.
Life under the ice
After a year of sampling, the results revealed an abundance of life with the team finding 130,000 cells in each millilitre of lake water with nearly 40,000 bacteria and archaea. The sample also showed that life has survived in the lake without solar energy for the past 120,000 years and possibly even 1 million years.
Over the past year, researchers have isolated and grown cultures of about a dozen species of microbes and DNA sequencing has revealed signs of nearly 4,000 species, many of them known microbes that break down minerals for energy, as there is no sunlight.
One main question for the scientists is whether these forms of life are classified as ‘survivors’ or ‘arrivers’, where survivors are descendants of microbes that lived in the sediments when the area was covered by the ocean compared to arrivers who would have been deposited on the ice after working their way down over the past 50,000 years as ice melted off the bottom of glaciers.
Alternatively, arrivers could have entered the lake from sea water seeping under the ice sheet, possible given Lake Whillans is 100 kilometres from the grounding line where the ice sheet transitions from resting on the ground to floating on the ice.
Other important findings from the lake included finding traces of fluoride, providing possible evidence of hydrothermal vents in the area – important as they provide rich sources of chemical energy that can support exotic life – and small amounts of formate, a chemical that suggests the presence of methane, a greenhouse gas.
Estimates have been made that sediments under the Antarctic ice sheet contain hundreds of billions of tonnes of methane. This is an issue as global temperatures rise and Antarctic ice sheets begin to melt, unlocking methane as well as contributing towards global sea level rise.
The West Antarctic glacier system melting
In 2014, scientists released studies that revealed a large section of the glacier system in West Antarctic has started to collapse. Previously, scientists believed the 3.2 kilometre-thick glacier system would remain stable for thousands of years however new research suggests a faster time frame.
UC-Irvine Earth science professor and lead author of the study, Eric Rignot, warns that six large glaciers in the Amundsen Sea ‘’have passed the point of no return’’ with current estimates suggesting the glaciers could disappear within two centuries. If this happened the rest of the ice in West Antarctica would follow.
Meanwhile a study on the thinning of glaciers on the Southern Antarctic Peninsula has found a major portion of the region, since 2009, has destabilized with ice-mass loss of the marine-terminating glaciers rapidly accelerating.
Warm water contributing to melting
One answer as to how glaciers are melting rapidly is that warmer seawater is penetrating the glacier base. Researchers studying the Totten glacier in East Antarctica have found evidence that a trough has formed deep beneath the glacier with a tunnel allowing warmer sea water to penetrate the glacier base: During a voyage to Antarctic over the last Antarctica summer researchers found waters around the Totten glacier to be 1.5 degrees Celsius warmer than other areas.
This came as a surprise to the scientists as until recently the East Antarctica ice sheet was thought to be surrounded by cold waters and therefore very stable. As such, due to warmer waters ‘’the Totten glacier is the most rapidly thinning glacier in East Antarctica and this melt has the potential to drive substantial regional ice loss’’ according to Jason Roberts, an Australian Antarctic Division glaciologist.
Warmer and more productive ocean
New research has found that while rising global temperatures will intensify glacial melting, coastal Antarctic waters could become more productive. This is due to polynyas – an expanse of open seawater along the coast that is enclosed by floating sea ice and the continental shelf – forming. These formations are productive with an abundance of phytoplankton due to iron being pumped into them by glacier meltwater. This results in polynyas smelling like rotten eggs according to Kevin Arrigo, a biological oceanographer of Stanford University, due to the emissions produced by phytoplankton.
Using satellite data from 1997 to 2014 for 46 polynyas around Antarctica the researchers detected a strong correlation between productivity levels and the extent of glacial melt from adjacent glaciers. The scientists hypothesise that glacier meltwater enriches the waters of the polynyas with iron which acts like a fertiliser. The meltwater is a supplier or iron because as melting ice crawls towards the ocean it breaks down bedrock, which is full of iron, along the way. Glaciers also have iron trapped in their mass from the snow that has accumulated on ice sheets over thousands of years with falling snow trapping dust that is rich in iron.
Productive oceans acting as carbon sinks
The researchers speculate that as the ecosystem becomes more productive the more food will be available for organisms at the top of the food chain with Arrigo saying ‘’the largest density of penguins and seals are in the areas that polynyas are most productive’’. Another potential benefit is their role as carbon sinks as bodies of water with photosynthesis occurring act as carbon sinks. In particular, Arrigo claims that polynyas ‘’disproportionately suck atmospheric carbon dioxide’’ and so an increase in their productivity is most likely going to increase their ability to store carbon. Nonetheless, with polynyas being only a few hundred square kilometres in size Arrigo admits their impact will be only minimal.
