Bridget Hott 

As summer draws to an end and the days get shorter and a bit colder, it’s only right that the end of the Marine Ecosystem Diaries comes to a close with the polar seas. Far away from most human life, the polar seas are seen as barren lands with little to offer – this couldn’t be further from the truth. These regions are teeming with unique life and provide ecosystem services that benefit the entire world. Unfortunately, these pristine environments are some of the fastest changing habitats from the encroaching effects of climate change. Time isn’t exactly on our side, but with more global support and awareness, the polar seas have a chance to cool back down. 

First off, what are the polar seas? 

The term polar seas refers to the Arctic Ocean and the sea that surrounds Antarctica. At the surface, these two share the general characteristics of cold weather, frigid waters, extreme seasonality, and seasonal changes in sea ice, but beneath the surface things begin to change. Let’s take a deeper look. 

The World’s Smallest Ocean

Residing at the northern most point of the Earth, the Arctic Ocean is known for its vast amounts of sea ice, gorgeous wildlife, and indisputably how quickly it is being affected by climate change. Perhaps not so well known is that the majority of the Artic is an icy sea, surrounded by a small portion of land from Canada, Greenland, and Eurasia. The water here is made up of shallow, marginal seas, which are bodies of water that separate the coast from the open ocean, like the Baltic or Mediterranean Seas. This has led to a much more diverse group of organisms that are able to call these frigid waters home, including humans. The Arctic is home to 4 million indigenous people (Antarctica has zero) who have been there for millennia, finding many ways to make such an inhospitable environment home. 

The World’s Newest Ocean

Far, far down south, we find Antarctica. Where the penguins march and few select researchers are able to call home for small portions of the year. The exact opposite of the Arctic, Antarctica is comprised of icy land surrounded by the ocean, an ocean that is on average 3 times deeper than the Arctic. The sea down here is known as the Southern Ocean, which was officially recognized worldwide as the 5th ocean this past year. Conditions down south are even more bleak than up north. The ocean is constantly riddled with strong winds, big waves, and intense storms, with water temperatures dropping as low as -2oC. Arguably the coolest (no pun intended) thing about Antarctica is the Antarctic Circumpolar Wave, a wave that continually circles the Earth every eight to nine years and controls temperatures in the overlaying atmosphere, so much so that scientists believe it could have a greater influence on rainfall than El Nino, particularly in southern Australia and New Zealand.

Life in the Polar Seas 

Despite their differences, some aspects of the polar seas are identical. For instance, both regions see limitations in biological productivity as a result of low light during portions of the year and sea ice blocking the sun. Fortunately, microbial productivity can function with little light which is why it is the main driver of productivity in these regions. Another similarity is found in ice melt from retreating sea ice. Phytoplankton find these conditions ideal and have population blooms, known as marginal-ice-zone associated blooms, which also happen in the ocean during spring and summer. Both of these mechanisms form the base of the food web in polar seas but, that’s where the similarities begin to dwindle in terms of common life forms. 

The Arctic sees species like whales (beluga, bowhead, California, gray), narwhal, orca, polar bears, sea otters, seals (ringed, bearded, ribbon, spotted), walrus, seabirds (tutted puffin, laysan albatross, spectacled eider), fish, crustaceans, mollusks. Because of the shallow seas within the Arctic Circle, bottom-dwelling species like polychaetes, brittlestars, amphipods, sponges, anemones, and even corals are found scattered along the seafloor, attracting some of the species listed above that prey on benthic creatures. 

In Antarctica, one can expect to find large marine mammals and little on the seafloor, as most life resides within the water column. Species found in Antarctica include at least 5 types of seals (crabeater, leopard, ross, weddell, elephant), six varieties of penguins (adelie, chinstrap, emperor, gentoo, macaroni, king), four whale species (blue, sperm, mink, southern bottlenose), orca, squid, fish, krill, diatoms, and seabirds.

Fun Fact: Orcas are found on every continent and in every climate, patrolling waters from polar to tropical, and are one of the few species found in both of the polar seas. 

Ecosystem Services 

Though far away from most human life, the polar seas play a great role in maintaining a stable planet. 

The Antarctic Circumpolar Current is one of the most important currents on the planet being the only current that flows completely around the globe and the current that transports the most water. It flows from east to west around Antarctica, pulling warm water in from the Atlantic, Pacific, and Indian oceans and cools them down to help keep Antarctica frozen, which, in turn, keeps the global climate stable.

Ice cover is also crucial to the survival of species that live in these regions. Large patches and sheets of ice are used as rest stops for migrating birds, mating and nursery grounds for marine mammals, and recharge stations between feeding points for mammals like polar bears, penguins, walrus, and seals. Even the underside of the ice is important, as it is home to millions of planktonic species that form the base of the food web in polar waters, sustaining krill and other prey species that inevitably go on to nourish open ocean communities, commercial fisheries, and larger marine mammals, like the gray whale.  

Aside from life sustaining capabilities, the polar seas are also known for their proficiency in capturing carbon. Each year, the Artic sequesters 58 megatonnes of carbon, and it does so using a biological pump, a concept briefly discussed during Deep Sea month. Antarctica also sequesters carbon through a biological pump, and studies suggest that the increased productivity from changes in sea ice draws extra CO2 out of the atmosphere which has been slowing the rate of global atmospheric CO2. The carbon sequestration abilities of the Southern Ocean is so powerful, some scientists believe it could be responsible for half of all CO2 absorption in the global ocean. 

Threats 

Like most habitats on Earth, the main threats facing the polar seas are climate change and human activity, like increased shipping traffic, tourism, and overbearing fishing industries. Since the 18th century, human activity has had an alarming rate of utilization on the living resources in polar environments. Practices like sealing, whaling, fishing, and bird harvesting have all lead to severe depletions of marine mammal species, with the most drastic being the baleen whales, which were hunted to near extinction in the 1800s for their fat, which was useful for burning in lamps and making soaps. 

Climate change is also disproportionately affecting the polar seas, causing them to experience the highest rates of warming anywhere in the world. The Arctic Ocean has officially become the fastest warming location on the planet, and the Antarctic Peninsula has experienced the highest rate of atmospheric warming in the entire southern hemisphere. For example, between 1970 and 2017, the Southern Ocean accounted for 35-43% of the global heat gain in the upper 2000m of water, despite accounting for roughly 25% of the global ocean area. Additionally, since the 1950’s, the Antarctic Peninsula air temperature has risen by 6oC, lost 6 ice shelves and continual glacial retreat. Up north, in June 2020, scientists recorded the hottest ever temperatures above the Arctic, a comfortable 38.6oC. Some scientists believe that with the current rate of warming and ice melt, ships could sail through open ocean directly to the North Pole by the year 2040, a feat that has historically been impossible. 

Conservation

There is still much to be learned about the polar seas, but with the latest developments in technology and melting sea ice allowing better access to the environments, more and more chilling discoveries are happening every day. With climate change closing in on our chance to study this invaluable ecosystem, conservation efforts are at an all-time high within these regions. Thanks to a recognized and globally shared view that these habitats need protection, several international conventions and governance mechanisms have been put in place. In 1946, the International Convention for the Regulation of Whaling (ICRW) placed a moratorium on whaling in all waters worldwide until populations rebounded from the drastic hits the whaling industry inflicted. In Antarctica, the Convention for the Conservation of Antarctic Marine Living Resources (CAMLR Convention) promotes “the preservation and conservation of living resources in Antarctica for future generations,” along with countless other agreements that protect the ecosystem. In the Arctic, the United Nations Convention on the Law of the Sea governs all activity in these waters, ideally protecting it from over-exploitation and other threats. However, unlike Antarctica, there is no treaty between the Arctic nations that watches over the region. With still plenty left to lose, the time to act on conservation for the polar seas is now.

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