The ocean east of Greenland is covered by ice all year round, with the white line showing the boundary of the oceanic ice. Credit: Marcello Passaro, Felix Müller / DGFI-TUM.

Researchers at Germany’s Technical University of Munich (TUM) have developed a new algorithm that can help radar satellites to accurately measure changes in sea level and ocean currents.

The Adaptive Leading Edge Subwaveform (ALES+) algorithm is expected to overcome the inability of current satellites to identify oceans underneath ice.

Existing radar satellites are unable to detect the covered oceans because ice reflects the altimeter satellite radar signals, making the water beneath the ice invisible. The satellites have been surveying the surfaces of the earth and oceans for more than two decades.

“We can use one and the same algorithm to measure sea level in both open and ice-covered ocean areas.”

ALES+ is capable of automatically detecting the portion of the radar signal that is reflected by water and obtains sea level values by using this information only.

The data analysis method also allows the satellite to precisely measure the height of the ocean water that reaches the surface through cracks and gaps in the ice.

TUM German Geodetic Research Institute representative Dr Marcello Passaro said: “The special thing about our method is that it is adaptive.

“We can use one and the same algorithm to measure sea level in both open and ice-covered ocean areas. ALES+ can also be used for coastal waters, lakes and rivers.

“Here the signals are highly varied, but always exhibit certain characteristic properties which the system then learns.”

ALES+ was developed with research from the Sea Level Climate Change Initiative of the European Space Agency.