In this video, we follow Dr Michel Tsamados on a journey through sea ice onboard the Polarstern ice breaker.

Sea ice extent and concentration is almost impossible to monitor at surface level, so EO is a vital method of gathering data on sea ice.

• Sea ice extent is based on whether an area is ‘ice-covered’ or ‘not ice-covered’. Typically, if an area has 15% coverage, it counts as ‘ice-covered’.
• Sea ice concentration is how much of a given area contains ice. This can be measured using optical imagery.

Optical remote sensing uses visible, near-infrared and short-wave infrared sensors to form images of the Earth, by detecting the solar radiation reflected from targets on the ground.

Optical sensors include the state-of-the-art MSI (Multispectral Imager) which is onboard Sentinel-2. This sensor provides high-resolution imagery. Additionally, the OLI (Operational Land Imager) is onboard Landsat-8.

The drawback of using optical sensing is that it is limited by cloud cover and images can only be taken during the daylight. This means that during polar night, when there are 24 hours of darkness for several weeks, optical sensing is useless.

Active microwave sensing can be used to detect sea ice. Satellites emit microwaves and they are reflected to the surface. Different surfaces scatter the microwaves differently, which allows the satellite to distinguish between different surfaces such as water or ice.

Objects on the Earth’s surface emit microwaves, and satellites can pick up these passive microwaves. For example, ice tends to emit more microwave energy than the oceans.

Recent studies suggest that sea ice extent is dropping rapidly, with the Arctic Sea ice cover dropping to 4.15m sq km on 18th September 2019 – 33% less than the 1981-2010 average minimum for that time of year.

For more information about how satellites monitor sea ice, watch Measuring Sea Ice Extent and Thickening. This topic is part of the Frozen Frontier: Monitoring The Greenland Ice Sheet from Space MOOC, also produced by Imperative Space, which is available freely if you are interested in learning more about the Greenland Ice Sheet.

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Featured Educator:

• Dr Michel Tsamados

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