ESA's CryoSat mission, with 14 years in space, provides one of the longest unbroken records of polar ice thickness. Recent research published in Geophysical Research Letters adds another capability to CryoSat: measuring light penetration through Arctic sea ice.
Julienne Stroeve of the University of Manitoba and the University of Colorado stated, "As ice and snow get thinner, more light penetrates to the bottom of sea ice. This changing light regime has the potential to impact the entire marine ecosystem, which all begins with algae."
Ice-bound algae bloom under the ice, forming the basis of an intricate food web. Zooplankton graze on the algae, feeding fish, seals, and ultimately polar bears. Understanding the impact of climate change on this ecosystem starts with studying algae.
Karley Campbell of the University of Tromso explained, "Unlike in the open ocean, we can't see the algae within sea ice from space. What we can do is start by estimating light availability. Light, harvested by ice algae to make organic compounds in photosynthesis, is a major factor driving marine production."
Using data from CryoSat, Copernicus Sentinel-3, and NASA ICESat-2, scientists estimated Arctic sea-ice thickness over CryoSat's 14-year mission. They developed models to predict light penetration through ice and snow, indicating when and where algae might bloom.
Data from 2011 to 2022 showed earlier algal blooms in more southerly Arctic regions, influenced significantly by snow cover. A snowy 2017, for example, resulted in deeper snow, preventing large areas from blooming due to insufficient light.
Researchers examined how declining snow depth since the 1980s affects algal blooms. Their model suggested blooms started up to 15 days earlier per decade in southern regions.
Understanding these changes involves considering various factors like sediment and ice structure, which affect light penetration. Ice-bound algae may produce different compounds or die off at different times due to increased light exposure.
Satellite measurements provide a broad picture of photosynthetically active radiation under ice, supporting other Arctic ecosystem studies. Julienne Stroeve noted, "Understanding the photosynthetically active radiation that penetrates sea ice will support wider studies to understand just what is happening to life in the Arctic Ocean due to climate change."
CryoSat's collaboration with ICESat-2 in the Cryo2ice mission will enhance snow cover estimates on ice. The upcoming Copernicus Polar Ice and Snow Topography Altimeter (CRISTAL) mission will continue mapping snow depth into the 2030s.
CryoSat Mission Manager, Tommaso Parrinello, stated, "After 14 years it's wonderful to see that CryoSat keeps on finding new applications. The rapid changes happening in the Arctic will have widespread consequences that affect all of us. Maintaining long-term satellite records is vital to help us understand them and navigate the future. I'm excited to see the impacts of the Cryo2ice collaboration in the coming months and years as well as the CRISTAL mission that will maintain the climate record beyond CryoSat."
Detailed graphics and captions can be found here at ESA
Research Report:Mapping Potential Timing of Ice Algal Blooms From Satellite
Related Links
CryoSat at ESA
Beyond the Ice Age
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