Navigating the polar frontier: exploring the effects of sea-ice decline on shipping and sea routes in the Arctic

Figure 1: Icebreaker traversing the Arctic Ocean, navigating the thick blanket of sea ice which obstructs its path [Credit: Christopher Michel/Flickr, CC BY 2.0].

Sea ice is a critical part of the unique Arctic ecosystem, but climate change is becoming a serious threat. Warming in the Arctic has already resulted in the loss of over 4 million km² of sea ice. But is it all bad? Retreat of Arctic sea ice is allowing more ships to navigate the Arctic Ocean, along shorter, faster and cheaper sea routes, providing emission reductions of 24%. But will the growth of shipping sign the death warrant for Arctic sea ice? Read on to find out!

A frozen landscape… on the edge?

Sea ice is a vital component of the unique Arctic ecosystem. Constrained to the Arctic Ocean, sea ice comprises a thick core surrounded by seasonal ice, which undergoes annual cycles of melting and freezing. Sea ice is critical – it’s what keeps the Arctic cold, reflecting heat energy from the sun with its bright white surface, and keeping the Arctic Ocean frozen throughout the year. However, a process called Arctic Amplification is threatening the sea ice. A concept associated with global warming, Arctic Amplification recognises that, in recent years, the Arctic has been warming faster than the rest of the world: Rantanen et al. (2022) suggest up to four times faster! This makes the Arctic particularly vulnerable: a warming world means melting ice, and less sea ice in the Arctic means that the sun’s heat energy is no longer reflected, but instead absorbed by the ocean. In a domino effect, a warming ocean then accelerates even more sea-ice melt, exposing more ocean, and causing more warming. It’s a dangerous loop, which could lead to rapid environmental change and an Arctic we no longer recognise.

A defrosting Arctic

Global warming has already had severe consequences. Since 1979, the winter sea-ice maximum extent retreated by 10%, and the summer minimum extent by 38%. That’s a loss of almost 1 million km² per decade, and total loss of 4.4 million km² over 40 years. To put that into perspective, that’s half the area of the USA, or half of Europe – the Arctic is undergoing some serious defrosting! In Figure 2, we can see just how far summer sea ice is retreating; since 1979, summer sea-ice extent has almost halved and is now almost completely constricted to the central Arctic Ocean.

Figure 2: Map showing September sea-ice extent from 1979-2019 at twenty-year intervals, supported by a graph showing annual sea-ice decline. [Credit: Lily Thompson].

Not only is sea ice retreating, but the rate of retreat is getting faster. Since 2000, we’ve seen two record-breaking low sea-ice extents (2012 and 2020), and every year we get a little bit closer to setting a new one (see Figure 2). Observations show that sea ice is retreating the fastest from the Russian and Canadian coastlines, where warming is greatest. Furthermore, Stroeve et al. (2014) reveal that the Arctic melt season has expanded from three to four months, with earlier sea-ice melt and delayed re-freeze, growing the summer period in which sea ice retreats. This means that ice has less time to re-form in the winter, meaning that it’s thinner, younger, and weaker every year. This is the vicious spiral we see today, where more warming = less sea ice = more warming.

Polar Pathways

The Arctic also accommodates various waterways (see Figure 3). Its longest passage, the Northern Sea Route, runs along the Russian coastline. Stretching 5600 km, it is a key feature of Russia’s Exclusive Economic Zone, as well as providing a maritime pathway connecting Europe and Asia. While the Northern Sea Route faces sea-ice obstructions, its potential as a shipping route is powered by its ability to reduce shipping distance and time by 50% compared to other global trade routes. In fact, using the Northern Sea Route beats shipping via the Suez Canal by 15 days, making it increasingly attractive to global trade. However, the remote location of the sea route poses challenges: narrow straits along the pathway demand ship size limitations, and with the Arctic region as a relatively new shipping location, it lacks port infrastructure. For these reasons, the Northern Sea Route has not yet reached its full potential.

Figure 3: Mapped pathways of Arctic seaways: the Northern Sea Route (dark blue), the Northwest Passage (light blue) and the Transpolar Sea Route (green). [Credit: Arctic Centre, 2023].

A second maritime route in the Arctic is the Northwest Passage. Navigating some of the 36,000 islands along the Canadian coastline, it stretches 1500 km. Its seven possible pathways include deep-water passages, seeking to avoid the ship-dimension restrictions experienced on the Northern Sea Route. However, the labyrinth of shallow, narrow channels characterising the Northwest Passage means that sea ice often blocks up the sea route, making reliable year-round shipping impossible. The Northwest Passage is thus fully reliant on the unpredictable distribution of sea ice every year.

There exists a third Arctic shipping route, however it is one that history is yet to traverse. The Transpolar Sea Route is 3800 km long, and directly crosses the North Pole – this pathway would represent the fastest journey across the central Arctic Ocean. However, there remains one HUGE icy problem… the entire route remains, to this day, blocked by sea ice. So what’s it worth? The Transpolar Sea Route is a frontier of the future, increasingly accessible as the Arctic continues to warm and the sea ice melts. It would require an icebreaker escort, but Bennett et al. (2020) suggest that summer use of the Transpolar Sea Route could be possible within 50 years.

So what’s the link?

The fact is that rapid sea-ice decline in the Arctic is what’s causing the marked rise in shipping through the Arctic Ocean. Observations show that shipping traffic has increased the most during the summer months, coinciding with the greatest annual losses in sea ice. Retreat of the ice away from the coastlines is opening up the waters along Arctic sea routes, making them more accessible and more reliable for shipping. The Northern Sea Route has seen particular growth, with a 540% increase in cargo volume along the pathway since 1980, as well as a growth in ship count of 72.5% on Canada’s Northwest Passage. On top of this, statistical analysis supports that the accelerated rate of sea-ice decline since 2000 is the direct cause of amplified shipping along Arctic sea routes with a confidence level of over 99%. This new open-water access has also enticed 8.3 million annual tourists to the Arctic region, and offers shipping emissions reductions of up to 24% through more direct routes.

So, it’s full steam ahead, right? Wrong. Shipping along Arctic sea routes is still highly vulnerable to unpredictability. Results show that in years with highly variable sea-ice extents, shipping traffic is massively reduced, with unpredictable sea ice making maritime transport unsafe and unreliable. In addition to this, the initial emissions-saving benefits of faster shipping in the Arctic are temporally limited: with more ships operating along these shorter transport routes, total emissions are actually rising. As a result, the environmental impacts of Arctic shipping beg the question of whether the shorter transport time is really worth it. Not only has reduced sea ice driven increased shipping, but increased shipping has further accelerated sea-ice decline, triggering exceptionally low sea-ice extents which present a threat not only to the Arctic marine ecosystem, but also to global temperature. By eliminating the critical reflective sea-ice surface, shipping is indirectly contributing to warming on a global scale, churning up the ocean surface to prevent sea-ice re-freeze. Therefore Arctic sea routes, despite their economic benefits, could have disastrous environmental effects, with localised impacts from shipping pollution exacerbating to global-scale climate warming. If these growing shipping trends continue, we are taking huge steps towards an unrecognizable, ice-free Arctic, after which there may be no chance of environmental recovery.

Future projections: an ice-free Arctic?

For sea routes to succeed, the Arctic will need to undergo considerable environmental change, with future warming continuing to accelerate sea-ice decline. However, these critical tipping points might be closer than we previously estimated. Models project that Arctic sea ice could retreat another 1.2 million km² by 2060, and almost 2 million km² by 2090 (see Figure 4). However, at its current rate of decline, we could see the Arctic reach the “ice-free” threshold (1 million km² total) as early as 2050. This change would mark a significant tipping point in the Arctic, after which it is uncertain as to whether the sea ice could recover to its previous extent.

Figure 4: Map showing projected sea-ice extent from 2019-2090 and resulting northwards migration of Arctic sea routes. [Credit: Lily Thompson].

As sea ice continues to retreat away from the coastlines, Arctic sea routes will be able to migrate northwards, leaving behind their shallow channels in favour of deep-water passages, unrestricted by sea ice. These future zones of shipping are highlighted in Figure 4, with the Northern Sea Route and Northwest Passage shifting towards the central Arctic Ocean. Not only does this allow even more ships to traverse the sea routes, but reduced sea-ice cover allows extension of the shipping season from the summer months through to the Arctic winter. As a result, more ships continue to churn up the ocean water during winter, preventing critical sea-ice formation, and further accelerating the rate of sea-ice decline. Eventually, we could reach a point where remaining sea ice is so thin, the Transpolar Sea Route could become navigable. While requiring an icebreaker escort, models predict the first summer Transpolar Sea Route navigation by 2030, with use as an operational shipping route by 2086. However challenges remain – the Transpolar Sea Route is brand new territory, unexplored and unsupported by coastal infrastructure (e.g. ports). It is also key to recognise that choosing to traverse this route would represent the end of the Arctic environment as we know it. Using icebreakers to navigate the Transpolar Sea Route would break up the last remaining core of Arctic sea ice (see map above); after that, it is only a matter of time before so little ice can re-form, we enter a new ice-free Arctic era, permanently environmentally transformed. We have no idea of the magnitude of impacts that an ice-free Arctic could trigger; what we do know is that losing the ice would rapidly amplify warming across the globe, which not only destroys the unique polar environment beyond recovery, but poses a threat to human life by intensifying the climate change we are already experiencing.

So what’s your verdict? Are the economic and time-saving benefits of Arctic shipping worth the potential environmental degradation? Important decisions being made now will shape the future of the planet – we must choose between human development and environmental protection, but only one of those things will benefit both people and planet in the long run.