Warming waters drive unprecedented algal blooms in Antarctica, scientists find
Scientists at the National Centre for Polar and Ocean Research (which comes under Ministry of Earth Sciences), located in Goa, have noticed the unprecedented algal blooms within sea ice sheet of Antarctica which they say is indicative of the warming climate in the region.
The algal bloom was noticed in the Maud Rise polynya, a large stretch of open water that is surrounded by ice, using satellite data to measure the concentrations of chlorophyll-a from 2017 onwards and are an indicator of warm water which helps algae propagate.
“Satellite derived chlorophyll-a concentration showed the new phytoplankton blooms reached up to 4.67 mg m-3. Multi-satellite data indicated that the bloom appeared for the first time since the entire mission records started since 1978,” Dr Babula Jena who led the research study said.
The bloom, he said was mainly a result of upwelling of warm water as well as a combination of factors like availability of nutrients and sunlight which only help the bloom grow further.
“The appearance of phytoplankton blooms within sea ice cover is of high importance with implications for atmospheric CO2 and global climate and demonstrates how the phytoplankton in the Southern Ocean would likely respond in the future under warming climate conditions and continued melting of Antarctic sea ice,” Dr Jena said.
A polynya is a ‘hole’ in the Antarctic sea ice that occurs if ice begins to melt in the middle of the ice sheet, rather than at the edges as is usually the case.
In September 2017, one such polynya - the Maud Rise - reappeared in mid‐September 2017 and grew to as large as 80,000 km2 by the end of October 2017, appearing like a large lake surrounded by sea ice. It is one of the largest known polynya and was last spotted in 1976.
Back then too, the scientists at the NCPOR accurately explained the sudden and ‘abnormal’ melting of ice at Maud Rise seemingly in the middle of an otherwise thick sea ice sheet, that published in Geophysical Research Letter.
It is within this polynya that the algal bloom has been recorded. Despite being high in nutrients, the seawater that surrounds Antarctica is not favourable for the growth of oceanic algae owing to the lack of sunlight and cold temperatures.
The blooms occurred in October-November of 2017 during the austral summer and spring in the southern hemisphere.
“With the frequent reoccurrence, the associated physical processes could possibly modify the region into a productive environment and likely have an impact on the regional ecosystem and carbon cycle. The occurrence of polynya and phytoplankton blooms may turn it into a potential sink of atmospheric CO2 through biological pumping and can be a major source of carbon and energy for the regional food web,” he added.
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