Algorithm finds missing phytoplankton in Southern Ocean

This still image is showing the concentrations of phytoplankton observed by satellites in the Southern Ocean. Credit: Robert Johnson 

NASA satellites may have missed more than 50% of the phytoplankton in the Southern Ocean, making it far more difficult to estimate the carbon capture potential of this vast area of sea.

But now, new research published in the Journal of Geophysical Research, Three improved satellite chlorophyll algorithms for the Southern Ocean, has led to the development of an algorithm that produces substantially more accurate estimates of Southern Ocean phytoplankton populations.

That research from the University of Tasmania's Institute for Marine and Antarctic Studies (IMAS) was led by PhD student Rob Johnson and Associate Prof Peter Strutton

"This new algorithm allows us to detect changes in plankton numbers that have previously gone unnoticed," said Johnson.

"This better understanding of the phytoplankton population will, in turn, allow us to gain a much more accurate idea of how much carbon this ocean can take up."

Phytoplankton
The importance of phytoplankton and their role in our planetary ecosystem cannot be underestimated.

They form the base of the marine food chain, produce half the oxygen on Earth and are partly responsible for the ocean uptake of at least a third of total human induced CO2 emissions.

So it was important to understand why existing ocean colour satellites systematically underestimated the chlorophyll concentration (a proxy for phytoplankton biomass) of the Southern Ocean and Antarctica.

To get the observations needed to make valid comparisons and develop the algorithm, the researchers used more than 1000 Southern Ocean phytoplankton samples collected over 10 years and compared these to satellite measurements.

Once this observational data was collected, the new algorithm was used to process satellite data and make comparisons.

It quickly became clear that the algorithm produced a much closer estimate of phytoplankton numbers than past satellite measurements.

ESA Envisat Images: Improve safety in icy Southern Ocean

An award-winning new website is using realtime imagery from ESA's Envisat satellite to provide a wealth of information on sea ice to aid safe passage through the treacherous waters of the Antarctic.

Although remote, the Southern Ocean is an increasingly busy route for sea traffic.

These seas are used more and more to conduct scientific research, transport freight, harvest fertile fishing grounds and carry tourists to experience one of Earth's last wildernesses.

However, ever-changing pack ice and icebergs pose a serious danger to marine safety – as demonstrated by the loss of the MS Explorer tourist ship in 2007

Owing to the remote and inhospitable nature of the Southern Ocean, satellite imagery offers the only real practical means of obtaining timely information on sea ice required for the safe passage of marine traffic. While safety may be a primary concern, so is cost, as sea ice can significantly delay passage times.

For some years, ESA has been providing these key data to aid navigation – but the 'Polar View' ice-monitoring service in the Antarctic has recently been greatly improved by a wealth of satellite images made accessible through a new interactive website.