Polynya: How Unfrozen Seawater Saves Life in the Cold
Polynya: How Unfrozen Seawater Saves Life in the Cold
In the middle of the hostile Arctic and Antarctic region, there is an oasis where life thrives. A polynya is an open-water area surrounded by sea ice and is home to a vulnerable ecosystem.
Due to Earth’s rising temperatures, more polynyas are appearing or becoming more extensive. However, that does not necessarily mean good news—even to the life it supports.
Polynyas are crucial to maintaining life in the Arctic and Antarctic region, and any disruptions, no matter how minor, can cause an extremely detrimental result.
To understand how ecologically vital these sea ice oases are, let us get to know them more.
Polynya Formation
Polynyas are open water areas in the Arctic and Antarctic regions where you expect ice to cover. Strong winds, freezing water temperatures, and heat create two kinds of these irregular openings.
For instance, scientists discovered a massive hole in the Arctic's oldest and thickest ice. A powerful storm caused a narrow crack on May 14, 2020. The robust Arctic winds were able to drag this crack open by the next day, creating a polynya around 30 km wide and 100 km long, revealing a block of 4-meter thick ice—which experts now consider as the last to remain in place during summer melting seasons.
Another way for polynyas to form is during sea-ice formation. The water begins to fill with crystals called frazils, which turn into sheets that solidify into floes. This is when ice gradually accumulates on the underside to form first-year ice, up to a meter thick, and are vulnerable, easy to melt, and easy to crack.
Wind and water currents can drive the floes into one another, where they crash together and create ridges up to 12 meters high and extend further below the surface. Eventually, the sea ice cracks, leading to a flaw lead. In some instances, strong winds and rising warm water opens up more extensive areas, which are polynyas.
Polynyas are mostly circular, but they can also have an irregular form. They also expand and contract depending on the very environment that created them in the first place. And according to the National Snow and Ice Data Center (NSIDC), “the water remains open because of processes that prevent sea ice from forming or that quickly move sea ice out of the region.”
How Polynya Supports Life
Some polynyas can support life, which is crucial for the Arctic and Antarctic regions to continue to thrive.
Newly formed polynyas can create ideal conditions that are crucial for life in the Arctic and Antarctic regions. Phytoplanktons flourish here, harboring various animals, from arctic cod, seals, walruses, polar bears, and more, creating an oasis for the region’s coastal ecosystem.
The polynya food chain begins with phytoplankton, such as marine algae, a food source for zooplankton, krill, copepods, and other small animals. Fish and other larger animals then consume them later on.
Phytoplankton requires sunlight and nutrients to grow. During spring, the sun returns to the regions, with the sea ice shielding the ocean from the heat. Meanwhile, microorganisms use the nutrients to develop, forming the basis for organisms higher in the food chain.
So, the open waters of the polynyas get to have the first glimpse of light. It is where phytoplankton first blooms, attracting zooplankton and fish, providing a rich harvest for marine predators. It also includes access to birds and mammals in the otherwise ice-covered seas.
When cold, dense polar water sinks to the ocean bottom, forcing deep, nutrient-laden water to the surface, another source of nutrient-rich water appears. That is why, under the sea ice surrounding the polynya, scientists have found a notable amount of algae bloom, an underwater polar equivalent of the grasslands.
NSIDC reports “a NASA-sponsored mission, Impacts of Climate on EcoSystems and Chemistry of the Arctic Pacific Environment (ICESCAPE), discovered a massive bloom in the Chukchi Sea, under a layer of Arctic ice.”
Polynyas can only be a rich oasis depending on the physical forces that shaped its environment. When the ice melts during spring, the meltdown water lets the phytoplanktons stay near the surface, where light can easily reach them.
However, environmental factors like strong winds, iceberg motions, and ocean currents can disrupt this process. As a result, the surface waters can mix, destroying the fresh, buoyant layer and mixing the phytoplankton deeper and away from the light.
For that reason, not all polynyas can support life. Polynyas with turbulent, high mixing, and low light environments are not ideal for flourishing ecosystems. Instead, polynyas with calm, intense mixing, more light, and high growth conditions are perfect.
Kinds of Polynyas
Aside from their nourishing factors, the process of its formation leads to two different kinds of polynyas. The classification depends on the “mechanism of ice removal,” says NSIDC.
Here are the two kinds of polynyas:
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Sensible-heat polynya
The polynyas that you often see in the middle of a vast sheet of sea ice are sensible-heat polynyas. These are open-water polynyas, which result when water above freezing goes up to the surface. Instead of continuing into ice formation, the warm surface water melts any new ice, preventing the hole from closing up.
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Latent-heat polynyas
These kinds of polynyas are coastal polynyas. Latent-heat polynyas appear when matter (ice) changes form but not due to temperature, but a change of state instead. Winds blowing persistently strong enough in one direction push the ice away from a barrier, which can be the coast, a glacier, or newly-formed sea ice. Any new ice sheets that appear on the surface are moved leeward or towards the direction that the wind is blowing, hence stopping the formation of new ice.
Simply put, open-water polynyas form from temperature interference. Meanwhile, coastal polynyas are from the changing of state due to matter.
Global Warming and Polynyas
If climate change and global warming continue, polynyas will become black holes instead of an oasis.
The polynya scientists discovered in the Arctic on May 14, 2020, rapidly closed by May 26. However, its very existence offers a notable and horrifying concern about how much our warming world is changing the Arctic and Antarctic regions completely.
The disappearance of the Arctic’s last ice
This polynya was discovered off the coast of Ellesmere Island, which has a block of 5-year-old sea ice. But, “North of Ellesmere Island, it's hard to move the ice around or melt it just because it's thick, and there's quite a bit of it,” said study lead author Kent Moore, an Arctic researcher at the University of Toronto-Mississauga in a press release.
Meaning, polynyas are scarce in that region, and the formation of a big hole like that means the ice has been thinning since 1988 and 2004 due to the rapid warming in northern latitudes.
The problem is, this is the Arctic’s last ice. At this rate, researchers predict that it may melt each summer completely. It is a bad sign for life in and out of the polynyas because as the open-water area grows more extensive, Moore says, “species like walruses and seabirds lose access to it, and eventually it gets so warm that species can’t survive.”
Climate change
With the warming climate in the Arctic, ice melts, and sea levels rise. But aside from that, it also brings climate change to the world.
One example would be the severe winter weather in the northern hemisphere. Climate change increases the likelihood of winds from the north pole stretching down, causing extreme cold weather events in the United States (like the Texas cold wave), more snowfall in Siberia, and unexpected colder weather in Asia.
Because of human-caused global warming and over-tilling lands for agriculture, heat blobs are forming in the nordic and Arctic seas, thinning the sea ice and soon forming more polynyas.
Marco Tedesco, a glacier expert at Columbia University and NASA scientist, said in The Guardian, “The action is clear – we need to get to net-zero emissions, but also we need to protect exposed populations along the coast. This is going to be a huge problem for our coastal cities.”
At this rate, polynyas will turn into black holes of the Arctic and Antarctic region instead of being an oasis. And as they get bigger and as more sea ice melts, it will change ocean currents, disrupt marine ecosystems, and threaten low-lying coastal cities by flooding—changing the world as we know it.
Following a more sustainable lifestyle and going green can be a big help in lessening your carbon footprint. We at Wave Tribe offer eco-friendly gear made of sustainable, natural and recycled materials for your surfing needs. We created a durable eco leash out of recycled ocean trash, and we use hemp fiber for our surf bags.
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