We all know that Antarctica is supposed to be mostly white due to ice and snow. But if we look at these new findings, we may find this area partly green (or fully green) in the future. Because of rising temperatures, two native plant species thrive and keep spreading across the continent.
Between 2009 and 2019, plant cover has increased more than in the last 50 years combined. It correlates with rising air temperatures and the decline of fur seal populations.
The recent study, published in Current Biology, showed the accelerated impacts of global warming in polar ecosystems. Lead author Nicoletta Cannone said, “Antarctica is acting as a canary in a coal mine.”
Two aforementioned native plant species that keep growing are Antarctic hair grass and Antarctic pearlwort. Apart from being the only plants endemic on the southernmost continent, they can withstand the continent’s frigid temperature and photosynthesize at temperatures below zero while covered in snow.
Researchers focused their observations on these plants on Signy Island. They compared the plants to detailed records accounting for plant growth noted since the 60s. Then, the team found that those plants flourish in a warmer climate.
The pearlwort, which is a small plant with yellow blossoms, has grown five times faster. On the other hand, the hair grass has grown ten times more in the past decade than in other years.
Not so immune after all
Previously, scientists thought that this other polar region was impervious to the effects of global warming. Only recently studies have shown that the continent has warmed up three times faster than the rest of the world within the last three decades.
Moreover, Antarctica has seen a record amount of ice loss. Between 2008 and 2015, ice loss increased by 36 billion gallons per year.
To be more precise, the team believed that the main cause of the plants’ increasing spread is warming summer air. In the past decade, summer temperatures on Signy Island have increased between .36 Fahrenheit to .49 Fahrenheit each year with the exception of one cold spell recorded in 2012.
Generally, Signy Island’s mean annual average air temperature has increased by 1.8 degrees Fahrenheit between 1960 and 2018.
Other things that may have contributed to even more plant growth in this icy continent are the decreasing fur seal populations. When this species doesn’t keep occupying the island, it means that there are fewer plants to be trampled over.
Nonetheless, warmer temperatures are the primary cause and most evident link. And consequently, they could be problematic for the fragile ecosystems.
Even though more plants may sound not too bad, that’s not exactly the case in Antarctica. When there’s an increase of plant species, there can be a change of chemical composition of the continent’s soils. In turn, this can alter how organic matter decomposes and degrade the permafrost. Additionally, higher temperatures may also pave the way for invasive species to outcompete native plants.
Global warming is a trouble for the polar continents because it doesn’t just melt the ice, but also bring forth other problems that will make matters worse. Aside from the plants we’ve talked about, it turns out that ice and ocean interactions could accelerate the melting.
West Antarctica keeps melting due to high melt rates of floating ice in the sea
A scientist team reported that the grounding line (where ice moves off the land and begins to float) of Pope Glacier retreated 3.5 kilometers in 3.6 months for an average of nearly 12 kilometers per year in 2017. Between 2016 and 2018, the western portion of Smith Glacier retreated at 2 kilometers per year and Kohler Glacier at 1.3 kilometers per year.
When the team observed the glacial retreats from 2018 to 2020, the rates slowed. However, the movement was still faster than anticipated by the glaciology community’s yearly numerical models.
Coauthor Eric Rignot said, “Alpine glaciers retreat by about 1 kilometer per century, so it’s alarming to see these Antarctic glaciers receding at as much as 12 times that rate per year. This pace is at the upper limit of what our models can replicate.”
Rignot and his colleagues surveyed the glaciers multiple times per year via synthetic aperture radar interferometry observations from Italy’s COSMO-SkyMed satellite system. Then they combined the data with digital elevation models of the ice surface generated through readings from the German Aerospace Center’s TanDEM-X satellite.
With it, the researchers could get valuable information about the movement of glacier grounding lines and ice sheet thickness since 2014.
How floating ice and seawater affect the melting
According to Rignot, the main culprit in the rapid glacier retreat is the interaction of floating ice and seawater. And, it’s more evident in newly formed cavities at the ice-ocean boundary.
“Pressurized seawater intrudes into sub-glacial gaps and melts grounded ice. This process has an added effect of reducing basal resistance, which speeds up glacier retreat,” said lead author Pietro Milillo.
Equivalent to about 6 centimeters of global sea level rise, the Pope, Smith and Kohler glaciers account for a relatively small contribution in the Amundsen Sea Embayment sector. But the physical dynamics of the retreat of these three smaller glaciers that were the focus of the study are also in effect for the Thwaites and Pine Island glaciers, according to Rignot.
“The destabilization of the Thwaites and Pine Island glaciers, which are also subject to rapid retreat from the intrusion of ocean water beneath the ice, can raise global sea level by more than a meter and cause the destabilization of a huge swath of West Antarctica. When that happens, which could be in as soon as a few years, we will have a major problem on our hands,” Rignot said.