It is the largest time series analyzed in a wide territory, which considered the entire Southern Ocean that surrounds the white continent. The study was published in Frontiers in Ecology and Evolution.
Daniela Jofré, IDEAL Center. The South Pole of our planet is a vast territory in constant change. Antarctica and the Southern Ocean comprise an area of millions of square kilometers which, in recent years, have been affected by various climatic, natural and anthropogenic phenomena. Therefore, it is vitally important to understand how these changes could modify the ecosystems present in it.
That is why, after the work done by various institutions, it was possible to analyze data of more than 20 years (from 1997 to 2019) of much of the southern tip of the Earth. For this, satellite images and data provided by buoys installed in different parts of the southern zone were used.
The research was carried out within the framework of the Marine Ecosystem Assessment of the Southern Ocean (MEASO), which defined 15 study regions divided into three zones: North, Subantarctic and Antarctic (below the Antarctic Circumpolar Current.) The data obtained analyzed variables such as chlorophyll concentration, an indicator of phytoplankton biomass, and primary production.
“For more than 20 years, the same technology was used in these three major areas in order to make long-term trend projections,” commented Dr. Juan Höfer, researcher at the Center for Dynamic Research on High Latitude Marine Ecosystems (IDEAL) of the Austral University of Chile (UACh) and co-author of the study.
The researcher, who is also an academic at the Pontifical Catholic University of Valparaíso (PUCV,) comments that “although there are previous studies that analyze specific areas of Antarctica and in periods of time of 15 years, this is the longest-standing work obtained to date and in a totally circumpolar area.”
Satellite observations showed the increase in phytoplankton in some areas of the Southern Ocean. However, there are more specific sectors (Ross Sea) where a decrease in these organisms has been detected. This could be due to the effects of climate change in the area. However, the same study suggests that analyzing this territory with a high level of precision is difficult to achieve, so long-term projections are still complex to define.
The research accounts for the difficulties of studying this large area of the globe, due to the fact that the physics of the seas differs drastically between regions of the Southern Ocean. Some areas have higher degrees of temperature than others, as well as the levels of sea ice, which also differentiates the phytoplankton communities present.
Dr. Höfer explains that “taking a long-term trend is complex and especially in a system as variable as the Southern Ocean, due to different factors: the interannual variability is quite strong, the area has a very marked seasonality and there are times of the year when satellite information cannot be obtained due to the little amount of light that reaches the area.”
Despite the difficulty of sampling a large area such as the extreme south, the research predicts changes in the seasonal patterns of production and in the microbial community in a period of 100 years, which will have ecological consequences, mainly in key species for Antarctic marine ecosystems, such as krill.
Another of the projections based on this research suggests a decrease in the production of Antarctic seaweed associated with sea ice, due to its decrease in recent years.
Dr. Höfer emphasizes on continuing with this type of research, despite the logistical difficulties that have arisen due to the pandemic. “To this day, even after obtaining this time series (the longest we have on record,) it is very difficult to differentiate the interannual variability from long-term change trends. Especially in times of climate change, it is important to continue analyzing the different factors that would influence the ecosystems of the South Pole.”
The study was published in the scientific journal Frontiers in Ecology and Evolution and included researchers from New Zealand, Australia, Norway and Chile.
Read the research here.