Jørgen Berge, University of Tromsø; Carlos Duarte, King Abdullah University of Science and Technology; Dorte Krause-Jensen, Aarhus University; Karen Filbee-Dexter, Laval University; Kimberly Howland, Université du Québec à Rimouski (UQAR) and Philippe Archambault, Université Laval
At just over 14 million square kilometers, the Arctic Ocean is the smallest and shallowest of the world's oceans. It's also the coldest. An extensive raft of sea ice swims near its center, expanding in the long, cold, dark winter, and contracting in the summer when the sun rises higher in the sky.
Every year, usually in September, the sea ice cover shrinks to its lowest level. The number in 2020 was a meager 3.74 million square kilometers, the second smallest measurement in 42 years, and about half by 1980. Every year when the climate warms , the Arctic is holding less and less ice.
The effects of global warming are being felt all over the world, but nowhere on earth are they as dramatic as in the Arctic. The Arctic is warming two to three times faster than any other place on earth, causing far-reaching changes to the Arctic Ocean, its ecosystems and the 4 million people who live in the Arctic.
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Some of them are unexpected. The warmer water pulls some species further north to higher latitudes. The thinner ice is moving more people across the Arctic on cruise ships, cargo ships and research vessels. Ice and snow can almost completely darken the water underneath, but climate change lets in more light.
Artificial light in the polar night
Light is very important in the Arctic. The algae that form the foundation of the Arctic Ocean's food web convert sunlight into sugar and fat and feed fish and ultimately whales, polar bears and humans.
In the high latitudes of the Arctic, the sun stays below the horizon for 24 hours in deep winter. This is called the polar night, and at the North Pole the year is simply a day that lasts six months followed by an equally long night.
Researchers studying the effects of ice loss deployed observatories – anchored instruments with a buoy – moored in an arctic fjord in the fall of 2006 before the fjord froze. When sampling began in spring 2007, the berths had been in operation for almost six months, collecting data during the long and bitter polar night.
What they discovered changed everything.
The polar night can last weeks and even months in the High Arctic. Michael O. Snyder, author provided
Life in the dark
At the time, scientists assumed that the polar night was absolutely uninteresting. A dead time in which life slumbers and the ecosystem sinks into a dark and cold standby mode. Not much was expected from these measurements, so the researchers were surprised when the data showed that life is not pausing at all.
Arctic zooplankton – tiny microscopic animals that eat algae – take part in a so-called diel-vertical migration under the ice and in the middle of the polar night. Marine animals in all of the world's oceans do this, migrating into the depths during the day to hide from potential predators in the dark, and emerging at night to feed.
Organisms use light as a guide, so logically they shouldn't be able to do this during the polar night. We now understand that the polar night is a riot of ecological activity. The normal rhythm of daily life continues in the dark. Shells open and close cyclically, seabirds hunt in almost total darkness, ghost shrimp and sea slugs gather in kelp forests to reproduce, and deepwater species like the helmet jellyfish surface when it's dark enough to be protected from predators.
For most organisms active during this time, the moon, stars, and aurora borealis are likely to provide important clues that determine their behavior, especially in parts of the Arctic that are not covered by sea ice. As the arctic climate warms and human activity in the region increases, these natural light sources will be invisible in many places and replaced by much stronger artificial light.
Almost a quarter of all land masses are exposed to scattered artificial light at night as it is reflected back to the ground by the atmosphere. There are few really dark places left, and light from cities, coasts, roads, and ships is visible into space.
Light pollution can even be felt in sparsely populated areas of the Arctic. Shipping routes, oil and gas exploration, and fishing all extend into the region as the sea ice retreats, drawing artificial light into the otherwise deep black polar night.
Creatures that have adapted to the polar night over millions of years are now suddenly exposed to artificial light. Michael O. Snyder, author provided
No organism has had the opportunity to properly adapt to these changes – evolution works on a much longer time scale. In the meantime, the harmonious movements of the earth, moon and sun have provided reliable indications for arctic animals for thousands of years. Many biological events, such as migration, foraging, and breeding, are heavily tuned for their gentle predictability.
In a recent study in the high Arctic of Svalbard between mainland Norway and the North Pole, it was found that the lights on board a research vessel affect fish and zooplankton at a depth of at least 200 meters. Disturbed by the sudden penetration of light, the creatures swirling beneath the surface reacted dramatically. Some swam towards the beam, others swam violently away.
It is difficult to predict what effects artificial light from ships that are new to the ice-free Arctic will have on polar night ecosystems that have known the darkness longer than modern humans. How the rapidly growing human presence in the Arctic is affecting the ecosystem is worrying, but there are also uncomfortable questions for researchers. If much of the information we have gathered about the Arctic comes from scientists stationed on brightly lit boats, how "natural" is the state of the ecosystem we have reported on?
Research in the Arctic could change significantly in the coming years to try to reduce light pollution. Michael O. Snyder, author provided
Arctic marine science is entering a new era with autonomous and remote-controlled platforms that can operate without light and take measurements in complete darkness.
As the sea ice retreats from the shores of Greenland, Norway, North America, and Russia, the open water periods become longer and more light reaches the sea floor. All of a sudden, coastal ecosystems that have been hidden under ice for 200,000 years see the light of day. This could be very good news for marine plants like kelp – large brown algae that thrive in cold water with enough light and nutrients.
Some seaweed species are anchored to the seabed and swim with the tide and current. They can grow up to 50 meters high – about the height of Nelson's column in Trafalgar Square, London. However, seaweed is typically excluded from the highest latitudes due to the shadow cast by sea ice and its abrasive effect on the seabed.
Badderlocks or winged seaweed off the coast of Nunavut in the Canadian Arctic. Ignacio Garrido / ArcticKelp, author provided
These lush underwater forests will grow and thrive as the sea ice shrinks. However, seaweed is not a new addition to the Arctic. They were once part of the traditional Greenland diet, and polar explorers and explorers observed them on the north coasts more than a century ago.
Some species of seaweed may have colonized the Arctic coasts after the last Ice Age or expanded out of small pockets that they held onto. Most Arctic kelp forests, however, are smaller and limited to patches in deeper waters compared to the huge swaths of kelp that line coastlines like California in the United States.
A diver explores a four meter high sugar kelp forest off Southampton Island, Canada. Ignacio Garrido / ArcticKelp, author provided
The latest findings from Norway and Greenland show that kelp forests are already expanding and increasing their reach towards the Pole. These ocean plants are expected to get bigger and grow faster as the Arctic warms, creating more corners for species to live in. The full extent of the Arctic kelp forests remains largely invisible and unknown, but modeling can help determine how much they have shifted and grown in the Arctic since the 1950s.
Known locations of kelp forests and global trends in forecast average summer surface temperature will increase over the next two decades according to IPCC models. Filbee-Dexter et al. (2018), author provided
A new carbon sink
Although large algae come in all shapes and sizes, many trees are remarkably similar, with long, stem-like but flexible bodies called stipes. The kelp forest canopy is filled with flat leaves like leaves, while forts act like roots by anchoring the algae to the rocks below.
Some species of arctic seaweed can grow over ten meters and form large and complex canopies suspended in the water column with a shaded and sheltered basement. Similar to forests on land, these marine forests provide habitats, nurseries, and feeding grounds for many animals and fish, including cod, pollack, crabs, lobsters, and sea urchins.
Kelp forests offer many nooks and crannies and surfaces to perch on, making them abundant in wildlife. Ignacio Garrido / ArcticKelp, author provided
Seaweed grows quickly, storing carbon in its leather fabric. What does your expansion in the Arctic mean for the global climate? Like restoring forests on land, growing underwater kelp forests can help slow climate change by removing carbon from the atmosphere.
Better still, some kelp material breaks off and is washed from shallow coastal waters into the deep ocean, where it is effectively removed from the earth's carbon cycle. The expansion of the kelp forests along the Earth's vast Arctic coasts could become a growing carbon sink that captures the CO₂ emitted by humans and locks it in the deep sea.
What happens to kelp in the Arctic is pretty unique – these ocean forests are contested in most other parts of the world. Overall, the global extent of kelp forests is declining due to ocean heat waves, pollution, warming temperatures, and eruptions of willows like sea urchins.
Unsurprisingly, it's not all good news. Penetrating kelp forests could drive away unique wildlife in the high Arctic. Algae living under the ice have nowhere to go and may disappear entirely. More temperate seaweed species can replace endemic Arctic seaweed species such as Laminaria solleidula.
A crab finds refuge on Laminaria solleidula – the only species of seaweed endemic to the Arctic. Ignacio Garrido / ArcticKelp, author provided
But kelp is just one group of species, many of which will penetrate further and deeper into the region as the ice melts.
Milne Inlet, on North Baffin Island in Nunavut, Canada, sees more maritime traffic than any other port in Arctic Canada. Most days during the open water period, 300-meter-long ships leave the iron-ore-laden port from the nearby Mary River Mine. Every year between 71 and 82 ships pass through the area, most of them go to – or come from ports in Northern Europe.
Cruise ships, coast guard ships, pleasure yachts, research icebreakers, cargo supply ships, and rigid inflatables full of tourists also glide through the area. Unprecedented warming and retreating sea ice have attracted new industries and other activities to the Arctic. In communities like Pond Inlet, maritime traffic has tripled in the past two decades.
Passengers from a cruise ship arrive in Pond Inlet, Nunavut. Kimberly Howland, author provided
These ships come to the Arctic from all over the world and carry a variety of water hitchhikers picked up in Rotterdam, Hamburg, Dunkirk and elsewhere. These species – some too small to be seen with the naked eye – are hidden in ballast water that is pumped into on-board tanks to stabilize the ship. They also adhere to the hull and other external surfaces in what is known as "biofouling".
Some survive the trip to the Arctic and are released into the environment when the ballast water is drained and the cargo is loaded. Those who hold on to the outer surface can release eggs, sperm, or larvae.
Many of these organisms are harmless, but some can be invasive newcomers that can cause harm. Research in Canada and Norway has already shown that non-native invasive species such as bay and acorn barnacles can survive ship transits to the Arctic. This increases the risk to arctic ecosystems as invasive species are a major cause of extinction worldwide.
Concerns about invasive species extend well beyond the Pond Inlet community. The Arctic is home to around 4 million people, many of them on the coasts, which provide nutrients and critical habitat for a wide variety of animals, from char and ringed seals to polar bears, bowhead whales and millions of migratory birds.
As the water warms up, the shipping season becomes longer and new routes such as the Northwest Passage and the North Sea Route (along the Arctic coast of Russia) open up. Some researchers expect that a transarctic route across the North Pole could be navigable by mid-century. Increasing shipping traffic increases the number and types of organisms transported into Arctic waters, and the increasingly hospitable conditions improve their chances of survival.
Prevention is the first way to keep invasive species out of the Arctic. Most ships need to treat and / or replace their ballast water with chemicals or other processes to limit the movement of harmful organisms to new locations. Guidelines also recommend that ships use special coatings on their hulls and clean them regularly to prevent biofouling. However, these preventive measures are not always reliable and their effectiveness in colder environments is little known.
The next best approach is to spot intruders as soon as possible as soon as they arrive to improve the chances of extermination or suppression. However, early detection requires extensive surveillance, which can be challenging in the Arctic. Keeping an eye out for the arrival of a new species can be like looking for a needle in a haystack, but northern communities may offer a solution.
Researchers in Norway, Alaska, and Canada have found a way to simplify this search by singling out species that have caused damage elsewhere and could withstand the arctic environmental conditions. Nearly two dozen potential invaders have a high chance of gaining a foothold in arctic Canada.
Among these is the cold-adapted red king crab, which is native to the Sea of Japan, the Bering Sea, and the North Pacific. It was intentionally introduced into the Barents Sea in the 1960s to start a fishery and is now spreading south along the Norwegian coast and the White Sea. It is a large, voracious predator that has been involved in a significant decline in harvested shellfish, sea urchins, and other larger, slow-moving soil species, and has a high probability of surviving transport in ballast water.
Another is the evergreen, which ruthlessly grazes on lush aquatic plants in coastal habitats, leaving bare or encrusted rocks behind. It also introduced a parasite on the east coast of North America that causes blackspot disease in fish, stresses adult fish and makes them uncomfortable, killing juveniles, and causing intestinal damage to the birds and mammals that eat them.
Track genetic remains
New species like this could affect the fish and mammals that humans hunt and eat when they arrive in Pond Inlet. After just a few years of navigation, a handful of potentially alien species have been discovered, including the invasive red-gilled mudworm (Marenzellaria viridis) and a potentially invasive tube amphipod. Both are known to reach high densities, alter the properties of seabed sediments, and compete with native species.
A cargo ship sails through Milne Inlet, Nunavut. Kimberly Howland, author provided
Baffinland, the company that operates the Mary River Mine, is trying to double its annual iron ore production. If expansion continues, up to 176 ore carriers will pass through Milne Inlet during the open water season.
While the future of Arctic shipping remains uncertain, it is an upward trend that needs to be watched. In Canada, researchers work with indigenous partners in communities with high shipping activity – including Churchill, Manitoba; Pond inlet and Iqaluit in Nunavut; Salluit, Quebec and Nain, Newfoundland – Building a network to monitor invasive species. One of the approaches involves collecting water and testing for genetic debris from dandruff, feces, sperm, and other biological material.
Pond Inlet and Salluit 2019 Field Team members filter eDNA from water samples taken from Milne Inlet. Christopher Mckindsey, author provided
This environmental DNA (eDNA) is easy to collect and can help identify organisms that would otherwise be difficult to capture or that are low in abundance. Technology has also improved basic knowledge of coastal biodiversity in other areas of high shipping, a fundamental step in identifying future changes.
Some alien species have already been identified in Churchill Harbor using eDNA monitoring and other sampling methods, including jellyfish, rainbow melt and an invasive species of copepod.
As part of the Arctic Council's Arctic Invasive Alien Species Strategy to Reduce the Spread of Invasive Species, efforts are being made to expand the network across the Arctic.
The Arctic is often referred to as the front line of the climate crisis, and because of its rapid rate of warming, the region has been hit by invasions of all kinds, from new species to new shipping routes. These forces could completely reshape the ocean basin in the lifetime of human beings today, from frozen, star-lit vistas populated by unique communities of highly adapted organisms to something entirely different.
The Arctic is changing faster than scientists can document, but there will be opportunities, such as growing carbon sinks, that could benefit wildlife and the people who live there. Not all changes in our warming world will be entirely negative. In the Arctic, as elsewhere, there are winners and losers.
Jørgen Berge, Vice Dean for Research, Arctic and Marine Biology, University of Tromsø; Carlos Duarte, Associate Professor of Marine Ecology at King Abdullah University of Science and Technology; Dorte Krause-Jensen, Professor of Marine Ecology, Aarhus University; Karen Filbee-Dexter, Marine Ecology Research Associate, Université Laval; Kimberly Howland, Research Associate / Associate Professor at Université du Québec à Rimouski (UQAR), and Philippe Archambault, Professor and Scientific Director of ArcticNet at Université Laval
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