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Arctic Ocean is turning green thanks to climate change

The Arctic, once a frozen expanse of white and blue, is undergoing a dramatic transformation. Thanks to climate change, this region is warming four times faster than the rest of the planet. As temperatures rise and ice retreats, a surprising new phenomenon is taking center stage: a massive bloom of algae beneath the thinning ice.

Unexpected consequence of Arctic melting ice

We’re all familiar with images of polar bears stranded on shrinking ice floes. But the impact of climate change on the Arctic Ocean goes far deeper than its most iconic inhabitants.

“As ice and snow gets 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,” explains Julienne Stroeve, a researcher from the University of Manitoba and the University of Colorado.

The algae form a vast, underwater “lawn” that thrives on the underside of the ice. Much like the phytoplankton that bloom in open oceans, these ice algae are the foundation of the Arctic food web. They feed zooplankton, which in turn nourish fish, seals, and ultimately, polar bears.

Revelation of algae blooms in Arctic

Mapping this underwater bloom has been a challenge, especially from space. 

“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,” remarks Karley Campbell, a scientist at the University of Tromsø.

This is where ESA‘s CryoSat satellite steps in. This remarkable mission has been monitoring Earth’s polar ice for 14 years, giving us one of the longest continuous records of ice thickness. 

Underwater algae in the Arctic Ocean seen by the BlueEye rover. Credit: BREATHE project
Underwater algae in the Arctic Ocean seen by the BlueEye rover. Credit: BREATHE project

Now, scientists have harnessed CryoSat’s data, along with information from Copernicus Sentinel-3 and NASA‘s ICESat-2, to model light penetration through the ice.

By combining this light data with models of snow and ice cover, researchers can predict where and when these algal blooms are likely to occur. The results are striking:

Earlier blooms

The Arctic is experiencing a warming trend, resulting in thinner ice and earlier melting. This allows more sunlight to reach the ocean waters beneath the ice, triggering earlier algal blooms, especially in the southern regions where warming is more pronounced.

Snow matters

Snow cover acts as a barrier to sunlight. In years with heavy snowfall, the thicker snow layer prevents light from reaching the water, delaying or even suppressing algal blooms. 

Conversely, years with less snow allow more light penetration, leading to earlier and potentially larger blooms.

Climate models predict a continued decline in Arctic snow cover over time. This decrease, coupled with the ongoing warming trend, suggests that algal blooms could start significantly earlier each decade. 

Some regions may experience blooms up to 15 days earlier every ten years due to the combined effects of less snow and thinner ice.

Ripple effects of a greener Arctic due to algae

The implications of these findings are far-reaching. Changes in the timing and extent of algae blooms can disrupt the delicate balance of the Arctic ecosystem. 

Algae exposed to more light may produce different nutrients, potentially impacting the entire food web.

“This unprecedented use of satellite data benefits our knowledge of the rapidly changing Arctic ecosystem,” Julienne Stroeve explains. 

“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.”

Arctic monitoring and algae growth

The collaborative efforts of CryoSat and ICESat-2, along with upcoming missions like CRISTAL, promise to give us even deeper insights into the Arctic’s changing environment. 

“The rapid changes happening in the Arctic will have widespread consequences that affect all of us,” notes Tommaso Parrinello, CryoSat’s Mission Manager.

As we continue to monitor the Arctic’s transformation, one thing is clear: the once-frozen north is becoming a greener, more dynamic ecosystem. 

The fate of this region is intertwined with our own, and understanding these changes is vital for navigating a future shaped by climate change.

The study is published in the journal Geophysical Research Letters.


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