Global warming triggered the thinning of Arctic ice and warm temperatures which caused phytoplankton blooms. Phytoplankton is growing underneath the sea ice layer and is bound to blossom even more in the future if the temperatures keep remaining above average. These phytoplankton blooms can determine major disturbance in the Arctic food chain.
Global warming boost phytoplankton blooms
Usually, phytoplankton should not develop underneath the sea ice since the ice reflects the sunlight and it does not allow it to penetrate the layer of ice. Nevertheless, over the last decades, Arctic sea ice became thinner and darker because of climate change, enabling more sunlight to penetrate it and reach the water underneath.
Massive and dark pools of water at the surface of the ice layers which are known as melt ponds have increased in number, covering a great surface and diminishing the reflectivity of the ice. The new research was published in the Science Advances magazine, indicating that the thin Arctic sea ice may be the one to be blamed for phytoplankton blooms.
The thin ice allows the sunlight to penetrate it and facilitate the growth of phytoplankton
Chris Horvat, the first author of the study and a researcher at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS), argued that environmentalists’ concern is connected to the question of how sunlight can penetrate through and be dispersed under sea ice. It is indeed the case that the thinning of the Arctic sea ice may contribute to the infiltration process. The layers of ice have thinned, and the number of melt ponds has grown.
Horvat pointed out that global warming made this area go from a state where there was no potential for plankton to grow to the point in which now large regions of the Arctic are now invaded by blooming phytoplankton. About twenty years ago, only 3 or 4% of the Arctic sea ice was as thin as today to allow the sunlight to penetrate and fuel the growth of phytoplankton, permitting the bloom of large colonies to develop.
Nowadays, researchers revealed that approximately 30% of the surface of sea ice layers which cover the Arctic Ocean allow major phytoplankton blooms in warm summer months. The mathematical method used by the team of researchers highlighted the idea that while melt ponds fuel the blooms, the responsible factor here is sea ice thickness.
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