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Copernicus Sentinel-2 helps research on algal blooms in Antarctica

19 December 2022

The Copernicus Sentinel-2 mission is helping to estimate snow algae in the Antarctic Peninsula for the first time ever—making a difference to researchers.

Algae are simple, tiny aquatic organisms that are primary photosynthetic producers and form the basis of many ecosystems on Earth. Individual algae are microscopic, but they can grow to such high concentrations that their blooms are visible from space.

Green Snowpacks on the Antarctic Peninsula

Research published in Nature Communications used data from the European Space Agency’s Copernicus Sentinel-2 satellites to generate the first estimate of the size and biomass of green snow algae in the Antarctic Peninsula.

This research focused on green algae on the Antarctic Peninsula, a 1,500-kilometre stretch of land in the northernmost region of Antarctica that points towards South America [1].

As the climate crisis raises Earth’s temperatures. Antarctica is predicted to lose 62% of blooms occupying small, low-lying islands that cannot expand their range to higher elevations.

Net positive increase in snow algae in Antarctica

The research found that algal blooms in the Antarctic Peninsula have ecological ties to marine communities and penguin colonies. As average positive summer temperatures increase within Antarctica, the area they inhabit also increases, which may contribute to glaciers melting.

At lower latitudes, algal bloom area and elevation were found to be increasing. This positive increase is expected to outweigh any losses, resulting in a net positive increase in the biomass of snow algae in Antarctica over the coming years.

Understanding how snow algae patterns are changing and how they fit into Antarctica’s biosphere, is critical to understanding the overall impact of a warming planet on Antarctica’s vegetation.

Key to these findings were remote sensing data from the Sentinel-2 mission of the European Union’s Copernicus Programme. The mission consists of two satellites in the same orbit around the poles. Named Sentinel-2A and -2B, they both utilise multispectral imaging technology to image land and coastal areas around the world with high optical resolution.

The data generated by these satellites have applications in agriculture, forest management and ecosystem monitoring and are made freely available to anyone around the world.

Over the coming years, two new satellites, Sentinel-2C and -2D will be launched to take up the relay from the first units.  

Sentinel-2 can image the entire Antarctic Peninsula every day

Lead researcher, Andrew Gray, from the School of Geosciences at the University of Edinburgh, says, “The advantage of Copernicus Sentinel-2 is that it provides continental coverage and a lot of data. Most fieldwork in Antarctica relies on research infrastructure, which limits areas of observations and results in largely anecdotal observations. We’ve now gone from that system, to being able to take a snapshot of where the distribution happens, namely why and where. That’s where the importance of high-resolution imagery comes in.”

Satellite Imagery of the Antarctic Peninsula

Snow algae are found in the summer, coastal snowpacks of Antarctica, though their distribution is global. However, it is hard for researchers to travel to these coastal snowpacks due to their inaccessibility. Despite these constraints, it is still possible to map out the region using remote sensing data.

Satellites such as Copernicus Sentinel-2 can image the entire Antarctic Peninsula every week at high resolution, allowing researchers to estimate data points such as are coverage, biomass estimates and seasonal development of green algal lifecycle stages. These factors can then also be related to snow temperature, aspect, latitude and elevation.

Ice-free ground makes up a very small percentage of the total land cover in Antarctica (0.18%). Even in the Antarctic Peninsula, the most vegetated region in Antarctica, only 1.34% of its exposed area is covered by photosynthetic organisms.

Snow algae are one of Antarctica’s primary photosynthetic producers

Previously studied areas have shown snow to host a wide array of different algal species and demonstrate ecological importance in relation to nutrient and carbon cycling for the continent. This makes snow algae one of the region’s primary photosynthetic producers and an important provider of nutrient provision for marine and terrestrial communities [2].

One important phenomenon brought on by increased algal bloom range and biomass is lowered albedo. Albedo refers to the fraction of light that is reflected off a body or surface, and in this case refers to the fraction of sunlight reflected off the Antarctic ice sheet.

In concert with algal blooms, the mixture of green algae with pure white ice sheets leads to ice sheet darkening and lowered albedo—anyone who has played sports on asphalt on a sunny day can attest to the fact that darker surfaces make the land hotter.

Over the coming years, researchers will continue to investigate the relationship between algal blooms and Antarctic icesheet melting.

Satellites offer us a unique vantage point in observing our planet, making large-scale research such as this possible. We are now able to see Earth in new ways and make exciting discoveries that have never been achievable before.

Validating the data

About the Copernicus Sentinels

The Copernicus Sentinels are a fleet of dedicated EU-owned satellites, designed to deliver the wealth of data and imagery that are central to the European Union's Copernicus environmental programme.

The European Commission leads and coordinates this programme, to improve the management of the environment, safeguarding lives every day. ESA is in charge of the space component, responsible for developing the family of Copernicus Sentinel satellites on behalf of the European Union and ensuring the flow of data for the Copernicus services, while the operations of the Copernicus Sentinels have been entrusted to ESA and EUMETSAT.

Did you know that?

Earth observation data from the Copernicus Sentinel satellites are fed into the Copernicus Services. First launched in 2012 with the Land Monitoring and Emergency Management services, these services provide free and open support, in six different thematic areas.

The Copernicus Land Monitoring Service (CLMS) provides geographical information on land cover and its changes, land use, vegetation state, water cycle and Earth's surface energy variables to a broad range of users in Europe and across the World, in the field of environmental terrestrial applications.

It supports applications in a variety of domains such as spatial and urban planning, forest management, water management, agriculture and food security, nature conservation and restoration, rural development, ecosystem accounting and mitigation/adaptation to climate change.

References:

[1] Gray, A., Krolikowski, M., Fretwell, P. et al. Remote sensing reveals Antarctic green snow algae as important terrestrial carbon sink. Nat Commun 11, 2527 (2020). https://doi.org/10.1038/s41467-020-16018-w

[2] Gray, A. et al. Remote Sensing Phenology of Antarctic Green and red snow algae using worldview satellites. Frontiers in Plant Science 12, (2021). https://doi.org/10.3389/fpls.2021.671981

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