A new study published in the journal Nature Geoscience has revealed that fluctuations in sea ice levels have been interconnected with periodic algae blooms and weather events linked to El Nino over the past twelve millennia.
By examining 170 meters of marine sediment cores extracted from Adélie Land in Antarctica by the Integrated Ocean Drilling Programme, scientists found that Antarctic winds strongly affected the melting of sea ice, which in turn influenced the levels of algae from the surface waters.
The researchers used CT scan imaging and analysis of microfossils and organic biomarkers to draw a detailed picture of the complex relationship between Antarctic winds, ice variations, and algae growth during the entire Holocene period.
A key finding was that until 4,500 years ago, algae bloom events occurred almost every year and were regulated by the periodic breakdown and melting of sea ice.
“While sea ice that persists from year to year can prevent these large algal blooms from occurring, sea ice that breaks out and melts creates a favorable environment for these algae to grow. These large algae ‘bloom events’ occur around the continent, form the base of the food webs and act as a carbon sink,” explained lead author Dr. Katelyn Johnson, a researcher at GNS Science in New Zealand.
These discoveries complicate our understanding of the present and future effects of climate change. According to co-author Dr. James Bendle from the University of Birmingham’s School of Geography, Earth and Environmental Science, while there is a clear relationship between temperatures rising in the Arctic and melting ice, the picture is more complicated in the case of the Antarctic.
“That’s because some areas of the Antarctic are warming, but in some areas sea ice has been increasing. Since sea ice reflects incoming sunlight, not only is the warming effect slowed down, but algae are unable to photosynthesize as easily. Climate models currently struggle to predict observed changes in sea ice for the Antarctic, and our findings will help climate researchers build more robust and detailed models,” explained Dr. Bendle.
Further research is needed to clarify how future long-term loss of sea ice due to global warming will affect food webs in the Antarctic, and how the carbon cycling processes will evolve in this region.