(The Conversation) – The oceans are heating up as the planet warms.

This past year, 2024, was the warmest ever measured for the global ocean, following a record-breaking 2023. In fact, every decade since 1984, when satellite recordkeeping of ocean temperatures started, has been warmer than the previous one.

A warmer ocean means increased evaporation, which in turn results in heavier rains in some areas and droughts in others. It can power hurricanes and downpours. It can also harm the health of coastal marine areas and sea life – coral reefs suffered their most extensive bleaching event on record in 2024, with damage in many parts of the world.

Warming ocean water also affects temperatures on land by changing weather patterns. The EU’s Copernicus Climate Change Service announced on Jan. 10 that data showed 2024 had also broken the record for the warmest year globally, with global temperatures about 2.9 degrees Fahrenheit (1.6 Celsius) above pre-industrial times. That would mark the first full calendar year with average warming above 1.5 C, a level countries had agreed to try to avoid passing long-term.

Climate change, by and large, takes the blame. Greenhouse gases released into the atmosphere trap heat, and about 90% of the excess heat caused by emissions from burning fossil fuels and other human activities is absorbed by the ocean.

But while it’s clear that the ocean has been warming for quite some time, its temperatures over the past two years have been far above the previous decades. That leaves two mysteries for scientists.

It’s not just El Niño

The cyclic climate pattern of the El Niño Southern Oscillation can explain part of the warmth over the past two years.

During El Niño periods, warm waters that usually accumulate in the western equatorial Pacific Ocean move eastward toward the coastlines of Peru and Chile, leaving the Earth slightly warmer overall. The latest El Niño began in 2023 and caused global average temperatures to rise well into early 2024.

But the oceans have been even warmer than scientists expected. For example, global temperatures in 2023-2024 followed a similar growth and decline pattern across the seasons as the previous El Niño event, in 2015-2016, but they were about 0.36 degrees Fahrenheit (0.2 Celsius) higher at all times in 2023-2024.

Scientists are puzzled and left with two problems to solve. They must figure out whether something else contributed to the unexpected warming and whether the past two years have been a sign of a sudden acceleration in global warming.

The role of aerosols

An intriguing idea, tested using climate models, is that a swift reduction in aerosols over the past decade may be one of the culprits.

Aerosols are solid and liquid particles emitted by human and natural sources into the atmosphere. Some of them have been shown to partially counteract the impact of greenhouse gases by reflecting solar radiation back into space. However, they also are responsible for poor air quality and air pollution.

Many of these particles with cooling properties are generated in the process of burning fossil fuels. For example, sulfur aerosols are emitted by ship engines and power plants. In 2020, the shipping industry implemented a nearly 80% cut in sulfur emissions, and many companies shifted to low-sulfur fuels. But the larger impact has come from power plants reducing their emissions, including a big shift in this direction in China. So, while technologies have cut these harmful emissions, that means a brake slowing the pace of warming is weakened.

Is this a warming surge?

The second puzzle is whether the planet is seeing a warming surge or not.

Temperatures are clearly rising, but the past two years have not been warm enough to support the notion that we may be seeing an acceleration in the rate of global warming.

Analysis of four temperature datasets covering the 1850-2023 period has shown that the rate of warming has not shown a significant change since around the 1970s. The same authors, however, noted that only a rate increase of at least 55% – about half a degree Celsius and nearly a full degree Fahrenheit over one year – would make the warming acceleration detectable in a statistical sense.

From a statistical standpoint, then, scientists cannot exclude the possibility that the 2023-2024 record ocean warming resulted simply from the “usual” warming trend that humans have set the planet on for the past 50 years. A very strong El Niño contributed some natural variability.

From a practical standpoint, however, the extraordinary impacts the planet has witnessed – including extreme weather, heat waves, wildfires, coral bleaching and ecosystem destruction – point to a need to swiftly reduce carbon dioxide emissions to limit ocean warming, regardless of whether this is a continuation of an ongoing trend or an acceleration.

Photo by Shifaaz shamoon on Unsplash

At the most northerly tip of the UK, looking north from the island of Muckle Flugga, Shetland, the cold wind whips up the sea and gannets dive.

While biodiversity loss in the Arctic Ocean may seem like a distant issue, the Shetland Islands lie further north than the Arctic Ocean’s southernmost waters.
The Arctic Circle is only 380 miles (610km) north of British waters – the same distance as London to Edinburgh by road.

Arctic wildlife is changing in ways that scientists like us don’t yet fully understand. Better protection for these species is urgently needed.

Establishing a new North Pole marine reserve where industrial activities such as shipping, oil and gas exploration and fishing are banned could provide an ocean sanctuary for wildlife.

Explorer-turned-conservationist Pen Hadow wants to create an internationally agreed marine reserve in the Central Arctic Ocean by 2037. He was the first person to trek solo from Canada to the geographic North Pole 21 years ago. The route he took in 2003 is no longer possible due to climate change.

In 2021, Hadow founded the 90 North Foundation, an environmental charity that is campaigning for a North Pole marine reserve to protect the Arctic’s peoples, its wildlife and its natural landscape.

Our team of marine researchers at the University of Exeter is collaborating with Hadow to explore how climate change will affect the ice and oceans in the Arctic and beyond.

Projected climate change poses great peril for wildlife such as polar bears and narwhals which are highly adapted to Arctic waters, relying on multi-year ice for foraging and breeding habitat.

So far, we have completed two ten-day surveys for whales and dolphins using both visual sightings and acoustic or sound monitoring underwater. We have also collected water samples to test for “environmental DNA” or eDNA. By filtering water and collecting small fragments of biological material, we can identity the presence of species by sequencing the trail they leave behind in the water in the form of fish scales, poo, skin or mucus, for example.

Once we have built a picture of where wildlife lives and how it moves about, changes in the Arctic ecosystem can be more easily monitored.

Arctic animals are also regularly spotted in British waters.

Ringed seals have been seen as far south as Cornwall. Beluga whales have been spotted off the coast of Shetland, and Atlantic white-sided and white-beaked dolphins frequently move between UK waters and the low Arctic. Bearded seals have been spotted in UK coastal waters, as have walrus and harp seals.

Brent geese, barnacle geese and pink-footed geese plus eider ducks, red knot, ringed plover and bar-tailed godwits all migrate between the Arctic and the UK. These birds breed in the Arctic and sub-Arctic, then overwinter in the UK and Ireland. These birds are particularly vulnerable because climate change is leading to wetter springs that can reduce their breeding success.

The wildlife living along UK’s shores is already changing as a result of climate change. Some species might expand their range northwards and this could further disrupt the Arctic ecosystem.

As well as monitoring wildlife, we are tracking the changing volume and routes of ships travelling through the Arctic Ocean. While our research is at an early stage, it’s already clear that industrial vessel activity in the Arctic Ocean is increasing as fishing vessels and cargo ships take advantage of the receding ice to make swifter routes across the globe.

The Arctic albedo

As the Arctic changes, the ramifications will be felt globally. The Earth’s northernmost white cap acts as a reflective shield against solar radiation. As the ice recedes, and the surface of the Earth darkens, so too does the planet’s in-built ability to reflect the sun’s warming rays.

Standing on a boat at the edge of the Arctic ice, we can see the powerful glow of sunlight reflecting from the icy surfaces. Any loss of this albedo (the ability of white ice to reflect sunlight and heat from the sun) triggers further warming, catalysing a negative feedback loop with profound implications. Rising temperatures can only be tackled by reducing greenhouse gas emissions.

Alongside this, we must protect the unique wildlife that have made the Arctic their home. A broad and encompassing approach to conservation of northern ecosystems could help limit the effects of human activities and the changing climate across the Arctic region and beyond. A well-connected global network of marine reserves that includes the Arctic Ocean is urgently needed.

Kirsten Freja Young, Senior Lecturer, Ecology, University of Exeter and Brendan Godley, Professor of Conservation Science, University of Exeter

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Featured image: Kirsten Young has been monitoring wildlife in the Arctic Ocean. Danielle Zalcman, CC BY-NC-ND.

Ocean-related tourism and recreation supports more than 320,000 jobs and US$13.5 billion in goods and services in Florida. But a swim in the ocean became much less attractive in the summer of 2023, when the water temperatures off Miami reached as high as 101 degrees Fahrenheit (37.8 Celsius).

The future of some jobs and businesses across the ocean economy have also become less secure as the ocean warms and damage from storms, sea-level rise and marine heat waves increases.

Ocean temperatures have been heating up over the past century, and hitting record highs for much of the past year, driven primarily by the rise in greenhouse gas emissions from burning fossil fuels. Scientists estimate that more than 90% of the excess heat produced by human activities has been taken up by the ocean.

That warming, hidden for years in data of interest only to oceanographers, is now having profound consequences for coastal economies around the world.

Understanding the role of the ocean in the economy is something I have been working on for more than 40 years, currently at the Center for the Blue Economy of the Middlebury Institute of International Studies. Mostly, I study the positive contributions of the ocean, but this has begun to change, sometimes dramatically. Climate change has made the ocean a threat to the economy in multiple ways.

“Boiling Shore,” Digital, Dream/ Dreamworld v3, 2024

The dangers of sea-level rise

One of the big threats to economies from ocean warming is sea-level rise. As water warms, it expands. Along with meltwater from glaciers and ice sheets, thermal expansion of the water has increased flooding in low-lying coastal areas and put the future of island nations at risk.

In the U.S., rising sea levels will soon overwhelm Isle de Jean Charles in Louisiana and Tangier Island in Chesapeake Bay.

Flooding at high tide, even on sunny days, is becoming increasingly common in places such as Miami Beach; Annapolis, Maryland; Norfolk, Virginia; and San Francisco. High-tide flooding has more than doubled since 2000 and is on track to triple by 2050 along the country’s coasts.

Rising sea levels also push salt water into freshwater aquifers, from which water is drawn to support agriculture. The strawberry crop in coastal California is already being affected.

These effects are still small and highly localized. Much larger effects come with storms enhanced by sea level.

Higher sea level can worsen storm damage

Warmer ocean water fuels tropical storms. It’s one reason forecasters are warning of a busy 2024 hurricane season.

Tropical storms pick up moisture over warm water and transfer it to cooler areas. The warmer the water, the faster the storm can form, the quicker it can intensify and the longer it can last, resulting in destructive storms and heavy downpours that can flood cities even far from the coasts.

When these storms now come in on top of already higher sea levels, the waves and storm surge can dramatically increase coastal flooding.

Tropical cyclones caused more than $1.3 trillion in damage in the U.S. from 1980 to 2023, with an average cost of $22.8 billion per storm. Much of that cost has been absorbed by federal taxpayers.

It is not just tropical storms. Maine saw what can happen when a winter storm in January 2024 generated tides 5 feet above normal that filled coastal streets with seawater.

What does that mean for the economy?

The possible future economic damages from sea-level rise are not known because the pace and extent of rising sea levels are unknown.

One estimate puts the costs from sea-level rise and storm surge alone at over $990 billion this century, with adaptation measures able to reduce this by only $100 billion. These estimates include direct property damage and damage to infrastructure such as transportation, water systems and ports. Not included are impacts on agriculture from saltwater intrusion into aquifers that support agriculture.

Marine heat waves leave fisheries in trouble

Rising ocean temperatures are also affecting marine life through extreme events, known as marine heat waves, and more gradual long-term shifts in temperature.

In spring 2024, one third of the global ocean was experiencing heat waves. Corals are struggling through their fourth global bleaching event on record as warm ocean temperatures cause them to expel the algae that live in their shells and give the corals color and provide food. While corals sometimes recover from bleaching, about half of the world’s coral reefs have died since 1950, and their future beyond the middle of this century is bleak.

Losing coral reefs is about more than their beauty. Coral reefs serve as nurseries and feeding grounds for thousands of species of fish. By NOAA’s estimate, about half of all federally managed fisheries, including snapper and grouper, rely on reefs at some point in their life cycle.

Warmer waters cause fish to migrate to cooler areas. This is particularly notable with species that like cold water, such as lobsters, which have been steadily migrating north to flee warming seas. Once-robust lobstering in southern New England has declined significantly.

In the Gulf of Alaska, rising temperatures almost wiped out the snow crabs, and a $270 million fishery had to be completely closed for two years. A major heat wave off the Pacific coast extended over several years in the 2010s and disrupted fishing from Alaska to Oregon.

This won’t turn around soon

The accumulated ocean heat and greenhouse gases in the atmosphere will continue to affect ocean temperatures for centuries, even if countries cut their greenhouse gas emissions to net zero by 2050 as hoped. So, while ocean temperatures fluctuate year to year, the overall trend is likely to continue upward for at least a century.

There is no cold-water tap that we can simply turn on to quickly return ocean temperatures to “normal,” so communities will have to adapt while the entire planet works to slow greenhouse gas emissions to protect ocean economies for the future.

Charles Colgan, Director of Research for the Center for the Blue Economy, Middlebury Institute of International Studies

This article is republished from The Conversation under a Creative Commons license. Read the original article.

(The Conversation) – Many experts believe we may soon face a mass extinction event, with a high proportion of Earth’s species dying out. Projections indicate the climate will continue to change for centuries to come, and this is a significant threat to biodiversity that has already had an impact on many species.

Despite the threat that climate change poses to biodiversity, we do not yet fully understand how it causes animals to go extinct. In our new paper, published in Science, we used the fossil record to make more precise estimates.

The geological rock record provides critical insight on past extinctions caused by a variety of climate change events. Fossils therefore offer a rare opportunity to understand the mechanisms of extinction and investigate how climate shifts have led to extinction in the past. Understanding why species went extinct under natural, pre-human conditions is paramount, since human-induced extinction drivers are accumulating over time.

By identifying which traits are linked to extinction, we can potentially use this knowledge to identify at-risk species to prioritise in conservation efforts.

In our latest research article, we analysed a data set comprising over 290,000 marine invertebrate fossils, covering the last 485 million years of Earth’s history. We looked directly for the traits most crucial for survival in the geologic past.

Previous studies have highlighted small body size and limited geographic range size (the spatial extent occupied by a species) as key predictors of extinction risk throughout geological history.

We reconstructed the climate for 81 geological stages across the Phanerozoic (the current geological era, starting 541 million years ago). And we used climate models to determine the range of temperatures that each species can endure.

Image by Robert Balog from Pixabay

These factors were then compared against geographic range size and body size to assess their relative importance. We then estimated an external factor that may impact risk of extinction: the magnitude of climate change experienced by each species.

We assessed how the intrinsic traits, such as temperature tolerance and body size, compared to climate change in affecting a species’ risk of extinction. Our study is the first to directly compare traits to external factors in determining what drives extinction.

Our findings revealed that species inhabiting climatic extremes, such as polar or equatorial regions, were particularly susceptible to extinction. Species with a narrow thermal tolerance of approximately less than 15°C faced a significantly higher risk of extinction. We also found that smaller-bodied species are more prone to extinction due to both climatic and other changes.

However, the most important predictor of extinction risk was geographic range size. Species with smaller ranges, occupying more geographically-confined areas, had a higher likelihood of extinction.

Conservation is needed

Alarmingly, our research has, for the first time, identified climate change as a significant predictor of extinction, alongside other species’ traits.

We observed that species subjected to local climate changes of 7°C or greater across geological stages were significantly more likely to face extinction. This suggests that surpassing this climate change threshold increases the likelihood of extinction for a species, regardless of its other traits.

That said, the research shows that there is a cumulative effect of these variables on extinction risk. This underscores the importance of considering a broad spectrum of factors when assessing vulnerability to extinction.

For instance, a species residing in polar regions, characterised by a small geographic range size and body size, and subjected to significant climate change, would face a higher extinction risk than what might be inferred if considering only its geographic range. This holistic approach reveals the interplay between various biological and environmental factors in determining species’ survival over geological timescales.

Our research underscores the urgent challenge climate change poses to global biodiversity. But it also emphasises the necessity for continued research.

Many uncertainties remain when it comes to extinction risk, particularly around why certain traits confer extinction resistance and how traits interact to effect extinction risk. This additional research is essential to fully leverage our study’s implications for conservation strategies.

Without immediate and targeted conservation efforts, informed by a deeper understanding, we risk moving toward a sixth mass extinction event. So our work provides a pivotal call to action. We should mitigate climate change, but also do more research to bolster our understanding of the impacts on vulnerable species.

Erin Saupe, Associate Professor, Palaeobiology, University of Oxford and Cooper Malanoski, PhD Candidate in Geology, University of Oxford

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Every year in the mid-latitudes of the planet, a peculiar phenomenon known as the phytoplankton spring bloom occurs. Visible from space, spectacular large and ephemeral filament-like shades of green and blue are shaped by the ocean currents.

The phytoplankton blooms are comprised of a myriad of microscopic algae cells growing and accumulating at the ocean’s surface as a result of the onset of longer days and fewer storms — often associated with the move into spring.

The timing of the phytoplankton spring bloom is, however, likely to be altered in response to climate change. Changes which will affect — for good or ill — the many species that are ecologically adapted to benefit from the enhanced feeding opportunity that blooms represent at crucial stages of their development.

Fine-tuned ecological adaptation

Phytoplankton blooms are, in some aspects, metronomes of the annual oceanic cycles around which many species’ biological clocks are synced to.

One example is the zooplankton Calanus finmarchicus, a class of micro-organism only capable of swimming up and down through the water column. Calanus finmarchicus usually spend the winter in diapause — the marine version of hibernation — surviving on their accumulated energy reserves in the deep ocean. At the moment they deem appropriate in the spring, they raise from the abyss to graze on the bloom and reproduce.

Fish and shellfish, too, are adapted to this natural metronome.

For some species, such as shrimp, females strategically lay their eggs in the water in advance of these blooms so their young will have ample food supplies from the moment they hatch

As incredible as it seems, some species can “calculate” the egg incubation period so that eggs hatch on average within a week of the expected spring bloom.

A question of timing

This, unfortunately, is where climate change is entering into the equation. What was normal in the past may well be changing more rapidly than marine species can adapt.

Zooplankton and fish larvae constitutes the bulk of what ocean scientists call secondary production. Secondary production is a key trophic level that links primary production (the phytoplankton using the sun’s light to produce biomass) and higher trophic levels, such as fish and marine mammals.

This grand relationship is known as a trophic cascade, as the zooplankton are eaten by the small fish and the small fish, in turn, are eaten by the bigger fish. A whole ecosystem beating on a clock largely determined by the timing of the phytoplankton spring bloom, hopefully in sync with the biological clocks of other species.

Any change to the timing of the spring bloom, for example as a result of climate change, can potentially have catastrophic consequences for the survival of zooplankton populations alongside the fishes and ecosystems which rely upon this abundant foodstuff.

This theory is known as the match/mismatch hypothesis and postulates that the consumer’s energy demand should “match” the peak resource availability

A new understanding

On the Newfoundland and Labrador shelf in the Northwest Atlantic, the spring bloom generally starts earlier in the south (mid-March on the Grand Banks of Newfoundland) and later in the north (late April on the southern Labrador shelf).

The south-to-north progression of the bloom was long believed to be related to the annual retreat of sea ice in the region.
But with the duration and spatial extent of the sea ice season being dramatically reduced in Atlantic Canada over the recent years, the relationship between sea ice and the timing of the bloom weakened.

I — alongside a team of researchers from across Canada — proposed a new theory to explain the initiation of the spring bloom on the Newfoundland and Labrador shelf.

Our theory points to transition from winter to spring as being key to trigger the bloom. In winter, cold and stormy conditions keep the ocean well mixed. However, the arrival of spring brings calmer winds and warming temperatures — coupled with increased freshwater flows. These conditions cause the ocean to reorganize into layers of different density — a phenomenon called re-stratification.

Re-stratification effectively prevents the phytoplankton cells of the upper layers from becoming easily mixed in the maelstrom of oceanic forces.
Their accumulation at the ocean’s surface creates the bloom.

This new mechanism successfully predicts the timing of the phytoplankton spring bloom over more than two decades. It also allows us to better understand the impacts that climate change is having upon our oceans.

Ecological significance

Located at the confluence of sub-arctic and sub-tropical ocean currents, the Newfoundland and Labrador shelf is naturally subjected to large fluctuations of its climate, with impacts on the timing of the bloom.

Our study has shown that a warmer climate is associated with earlier re-stratification, earlier phytoplankton blooms and a higher abundance of key zooplankton species such as Calanus finmarchicus in the region.

This discovery opens the door to a better understanding of bloom dynamics and the oceanic conditions driving the health of the ecosystem.

The good news for a cold region such as the Newfoundland and Labrador shelf is that a warmer climate with milder springs, like the ones we have seen in recent years, will lead to more and more abundant levels of phytoplankton — with clear benefits to ecosystem productivity.

However, for how long these changes will remain positive in a changing climate we cannot say.

Frédéric Cyr, Adjunct Professor, Physical Oceanography, Memorial University of Newfoundland

This article is republished from The Conversation under a Creative Commons license. Read the original article.

A heat wave in Greenland and a storm in Antarctica. These kinds of individual weather “events” are increasingly being supercharged by a warming climate. But despite being short-term events they can also have a much longer-term effect on the world’s largest ice sheets, and may even lead to tipping points being crossed in the polar regions.

We have just published research looking at these sudden changes in the ice sheets and how they may impact what we know about sea level rise. One reason this is so important is that the global sea level is predicted to rise by anywhere between 28 cm and 100cm by the year 2100, according to the IPCC. This is a huge range – 70 cm extra sea-level rise would affect many millions more people.

Partly this uncertainty is because we simply don’t know whether we’ll curb our emissions or continue with business as usual. But while possible social and economic changes are at least factored in to the above numbers, the IPCC acknowledges its estimate does not take into account deeply uncertain ice-sheet processes.

Sudden accelerations

The sea is rising for two main reasons. First, the water itself is very slightly expanding as it warms, with this process responsible for about a third of the total expected sea-level rise.

Second, the world’s largest ice sheets in Antarctica and Greenland are melting or sliding into the sea. As the ice sheets and glaciers respond relatively slowly, the sea will also continue to rise for centuries.

Photo by Cassie Matias on Unsplash

Scientists have long known that there is a potential for sudden accelerations in the rate at which ice is lost from Greenland and Antarctica which could cause considerably more sea-level rise: perhaps a metre or more in a century. Once started, this would be impossible to stop.

Although there is a lot of uncertainty over how likely this is, there is some evidence that it happened about 130,000 years ago, the last time global temperatures were anything close to the present day. We cannot discount the risk.

To improve predictions of rises in sea level we therefore need a clearer understanding of the Antarctic and Greenland ice sheets. In particular, we need to review if there are weather or climate changes that we can already identify that might lead to abrupt increases in the speed of mass loss.

Weather can have long-term effects

Our new study, involving an international team of 29 ice-sheet experts and published in the journal Nature Reviews Earth & Environment, reviews evidence gained from observational data, geological records, and computer model simulations.

We found several examples from the past few decades where weather “events” – a single storm, a heatwave – have led to important long-term changes.

The ice sheets are built from millennia of snowfall that gradually compresses and starts to flow towards the ocean. The ice sheets, like any glacier, respond to changes in the atmosphere and the ocean when the ice is in contact with sea water.

These changes could take place over a matter of hours or days or they may be long-term changes from months to years or thousands of years. And processes may interact with each other on different timescales, so that a glacier may gradually thin and weaken but remain stable until an abrupt short-term event pushes it over the edge and it rapidly collapses.

Because of these different timescales, we need to coordinate collecting and using more diverse types of data and knowledge.

Historically, we thought of ice sheets as slow-moving and delayed in their response to climate change. In contrast, our research found that these huge glacial ice masses respond in far quicker and more unexpected ways as the climate warms, similarly to the frequency and intensity of hurricanes and heatwaves responding to changes with the climate.

Ground and satellite observations show that sudden heatwaves and large storms can have long-lasting effects on ice sheets. For example a heatwave in July 2023 meant at one point 67% of the Greenland ice sheet surface was melting, compared with around 20% for average July conditions. In 2022 unusually warm rain fell on the Conger ice shelf in Antarctica, causing it to disappear almost overnight.

These weather-driven events have long “tails”. Ice sheets don’t follow a simple uniform response to climate warming when they melt or slide into the sea. Instead their changes are punctuated by short-term extremes.

For example, brief periods of melting in Greenland can melt far more ice and snow than is replaced the following winter. Or the catastrophic break-up of ice shelves along the Antarctic coast can rapidly unplug much larger amounts of ice from further inland.

Failing to adequately account for this short-term variability might mean we underestimate how much ice will be lost in future.

What happens next

Scientists must prioritise research on ice-sheet variability. This means better ice-sheet and ocean monitoring systems that can capture the effects of short but extreme weather events.

This will come from new satellites as well as field data. We’ll also need better computer models of how ice sheets will respond to climate change. Fortunately there are already some promising global collaborative initiatives.

We don’t know exactly how much the global sea level is going to rise some decades in advance, but understanding more about the ice sheets will help to refine our predictions.

Edward Hanna, Professor of Climate Science and Meteorology, University of Lincoln and Ruth Mottram, Climate Scientist, National Centre for Climate Research, Danish Meteorological Institute

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Amid the escalating threats of a warming world, and with the latest annual United Nations global climate conference (COP28) behind us, there is one critical message that’s often left out of the climate change discourse. Halting overfishing is itself effective climate action.

This argument is the logical conclusion of a plethora of studies that unequivocally assert that stopping overfishing isn’t just a necessity, it’s a win-win for ocean vitality, climate robustness and the livelihoods reliant on sustainable fisheries.

The intricate relationship between climate change and ocean ecosystems was the subject of recent collaborative research — led by researchers at the University of British Columbia — that highlighted the crucial links between overfishing and climate change.

Finding the connections

Our collaborative team of international researchers applied a host of methodologies ranging from literature reviews to quantitative and quality analysis. The findings of this research illuminate eight key multifaceted impacts.

1 — Ending overfishing isn’t merely an ecological imperative but a vital climate action. Doing so would bolster marine life resilience in the face of climate shifts and reduce associate carbon emissions.

2 — Large subsidized fishing boat fleets can actually be a burden on small-scale fisheries, leaving them disproportionately vulnerable to shocks. In turn, overfishing not only depletes resources but also escalates carbon emissions, intensifying climate impacts on these fisheries and their communities, particularly women.

Additionally, the vulnerability of shellfish fisheries to climate stressors further underscores the importance of adaptive strategies tailored to local conditions.

3 — Success stories, like the recovery of European hake stocks, reveal a direct tie between stock recuperation and reduced emissions intensity from fisheries. We must champion and also learn from these successes.

4 — Ecosystem-based fisheries management reverses the “order of priorities so that management starts with ecosystem considerations rather than the maximum exploitation of several target species.”

Ecosystem-based fisheries management has considerable potential to enhance sustainable catches while fostering carbon sequestration. This is perhaps best exemplified by the successful implimentation of ecosystem-based fisheries management in the western Baltic Sea.

5 — Heavy metal pollution in the ocean — such as mercury or lead waste — intensifies the negative impacts of warming and overfishing. This pollution reinforces the need for developing multifaceted regulations based around ecosystem and ocean sustainability solutions.

6 — Overfishing exacerbates climate and biodiversity threats. Climate change contributes to less defined and predictable seasons and is causing reproductive challenges and the propagation of diseases in fish populations — among other issues.

Via Pixabay. .

Adding to these problems, overfishing itself is altering ecological dynamics, modifying habitats and opening new pathways for invasive species. These compounding crises further exacerbate the impacts of overfishing on marine ecosystems while at the same time making fish populations more vulnerable to climate change.

The above factors all combine to reduce the catch potential in any given ecosystem. In turn, fishers are forced to venture farther and deeper in the ocean to fish — increasing carbon emissions, personal risk factors to fishers and bycatch concerns.

7 — International fisheries management must play a central role in promoting biodiversity and retaining the ocean’s carbon sequestration potential. While 87 nations have signed the UN’s Biodiversity of Areas Beyond National Jurisdiction Treaty (also known as the High Seas Treaty), only one has ratified it. This treaty must be fully ratified and its effective implementation should be contingent upon the creation of marine protected areas that cover at least 30 per cent of the high seas.

8 — The ocean has huge carbon sequestration potential. Shifting from the generally accepted maximum of sustainable yield management to maximizing carbon sequestration in fisheries management could further advance climate goals.

Future regulations should allocate a percentage of the annual fish quota to maintain the carbon sequestration function of marine animals. Simply put, beyond just being food, fish stocks serve vital carbon sequestration and biodiversity services that directly benefit humanity. Future regulations should reflect this reality.

A simple goal

This joint collaborative research underscores the urgency of this issue. Ending overfishing isn’t just an ecological imperative but a linchpin for climate action. Furthermore, fisheries aren’t mere victims in these dynamics, but have real agency to play a pivotal role in either exacerbating or mitigating climate change.

An ideal governance framework would focus on managing ecosystems with considerations for their diverse benefits, based on the best evidence available. Regulation of fisheries, while controversial, is essential to not overly exploit such a valuable public resource.

As we gear up to the next COP, we would do well to remember these conclusions. Without nurturing ocean life, addressing climate change becomes an uphill battle. Sustainable fisheries management is not just an ecological necessity. It is also the cornerstone of a resilient, sustainable future.

Rashid Sumaila, Director & Professor, Fisheries Economics Research Unit, University of British Columbia

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Superstorms, abrupt climate shifts and New York City frozen in ice. That’s how the blockbuster Hollywood movie “The Day After Tomorrow” depicted an abrupt shutdown of the Atlantic Ocean’s circulation and the catastrophic consequences.

While Hollywood’s vision was over the top, the 2004 movie raised a serious question: If global warming shuts down the Atlantic Meridional Overturning Circulation, which is crucial for carrying heat from the tropics to the northern latitudes, how abrupt and severe would the climate changes be?

Twenty years after the movie’s release, we know a lot more about the Atlantic Ocean’s circulation. Instruments deployed in the ocean starting in 2004 show that the Atlantic Ocean circulation has observably slowed over the past two decades, possibly to its weakest state in almost a millennium. Studies also suggest that the circulation has reached a dangerous tipping point in the past that sent it into a precipitous, unstoppable decline, and that it could hit that tipping point again as the planet warms and glaciers and ice sheets melt.

In a new study using the latest generation of Earth’s climate models, we simulated the flow of fresh water until the ocean circulation reached that tipping point.

The results showed that the circulation could fully shut down within a century of hitting the tipping point, and that it’s headed in that direction. If that happened, average temperatures would drop by several degrees in North America, parts of Asia and Europe, and people would see severe and cascading consequences around the world.

We also discovered a physics-based early warning signal that can alert the world when the Atlantic Ocean circulation is nearing its tipping point.

The ocean’s conveyor belt

Ocean currents are driven by winds, tides and water density differences.

In the Atlantic Ocean circulation, the relatively warm and salty surface water near the equator flows toward Greenland. During its journey it crosses the Caribbean Sea, loops up into the Gulf of Mexico, and then flows along the U.S. East Coast before crossing the Atlantic.

This current, also known as the Gulf Stream, brings heat to Europe. As it flows northward and cools, the water mass becomes heavier. By the time it reaches Greenland, it starts to sink and flow southward. The sinking of water near Greenland pulls water from elsewhere in the Atlantic Ocean and the cycle repeats, like a conveyor belt.

Too much fresh water from melting glaciers and the Greenland ice sheet can dilute the saltiness of the water, preventing it from sinking, and weaken this ocean conveyor belt. A weaker conveyor belt transports less heat northward and also enables less heavy water to reach Greenland, which further weakens the conveyor belt’s strength. Once it reaches the tipping point, it shuts down quickly.

What happens to the climate at the tipping point?

The existence of a tipping point was first noticed in an overly simplified model of the Atlantic Ocean circulation in the early 1960s. Today’s more detailed climate models indicate a continued slowing of the conveyor belt’s strength under climate change. However, an abrupt shutdown of the Atlantic Ocean circulation appeared to be absent in these climate models.

Ted-Ed Video: “How do ocean currents work? – Jennifer Verduin”

This is where our study comes in. We performed an experiment with a detailed climate model to find the tipping point for an abrupt shutdown by slowly increasing the input of fresh water.

We found that once it reaches the tipping point, the conveyor belt shuts down within 100 years. The heat transport toward the north is strongly reduced, leading to abrupt climate shifts.

The result: Dangerous cold in the North

Regions that are influenced by the Gulf Stream receive substantially less heat when the circulation stops. This cools the North American and European continents by a few degrees.

The European climate is much more influenced by the Gulf Stream than other regions. In our experiment, that meant parts of the continent changed at more than 5 degrees Fahrenheit (3 degrees Celsius) per decade – far faster than today’s global warming of about 0.36 F (0.2 C) per decade. We found that parts of Norway would experience temperature drops of more than 36 F (20 C). On the other hand, regions in the Southern Hemisphere would warm by a few degrees.

These temperature changes develop over about 100 years. That might seem like a long time, but on typical climate time scales, it is abrupt.

The conveyor belt shutting down would also affect sea level and precipitation patterns, which can push other ecosystems closer to their tipping points. For example, the Amazon rainforest is vulnerable to declining precipitation. If its forest ecosystem turned to grassland, the transition would release carbon to the atmosphere and result in the loss of a valuable carbon sink, further accelerating climate change.

The Atlantic circulation has slowed significantly in the distant past. During glacial periods when ice sheets that covered large parts of the planet were melting, the influx of fresh water slowed the Atlantic circulation, triggering huge climate fluctuations.

So, when will we see this tipping point?

The big question – when will the Atlantic circulation reach a tipping point – remains unanswered. Observations don’t go back far enough to provide a clear result. While a recent study suggested that the conveyor belt is rapidly approaching its tipping point, possibly within a few years, these statistical analyses made several assumptions that give rise to uncertainty.

Instead, we were able to develop a physics-based and observable early warning signal involving the salinity transport at the southern boundary of the Atlantic Ocean. Once a threshold is reached, the tipping point is likely to follow in one to four decades.

The climate impacts from our study underline the severity of such an abrupt conveyor belt collapse. The temperature, sea level and precipitation changes will severely affect society, and the climate shifts are unstoppable on human time scales.

It might seem counterintuitive to worry about extreme cold as the planet warms, but if the main Atlantic Ocean circulation shuts down from too much meltwater pouring in, that’s the risk ahead.

This article was updated on Feb. 11, 2024, to fix a typo: The experiment found temperatures in parts of Europe changed by more than 5 F per decade.

René van Westen, Postdoctoral Researcher in Climate Physics, Utrecht University; Henk A. Dijkstra, Professor of Physics, Utrecht University, and Michael Kliphuis, Climate Model Specialist, Utrecht University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

The health benefits of eating seafood are appreciated in many cultures which rely upon it to provide critical nutrients vital to our physical and mental development and health. Eating fish and shellfish provides significant benefits to neurological development and functioning and provides protection against the risks of coronary heart disease and Type 2 diabetes.

Over three billion people get at least 20 per cent of their daily animal protein from fish. In countries from Bangladesh to Cambodia, Gambia, Ghana, Indonesia, Sierra Leone and Sri Lanka, fish consumption accounts for 50 per cent or more of daily intake.

However, expansive growth of human populations globally puts immense pressure on the health of wild fish stocks. Fish catches peaked in 1996, and one-third are considered overexploited. With less fish available to still more people, the future of fish as an accessible source of nutritious food is at risk, particularly among low-income countries.

Seafood nutrient losses

Threats to seafood access aren’t just due to overharvesting. There is a growing body of research showing that higher water temperatures due to climate change can impact the presence and abundance of the catch, through shifts in species distribution and changes in the species caught. This impacts the amount that can be harvested, as well as the nutritional value of that harvest.

A new study (which Aaron MacNeil contributed to) quantified nutrient availability from seafood through time considering the twin impacts of overfishing and climate change.

Focusing on four key nutrients important to human health — calcium, iron, omega-3 fatty acids and protein — the authors argue that nutrient availability in seafood has been declining since 1990 and will further decline by around 30 per cent by 2100 in predominately tropical, low-income countries with 4 C of warming.

These predicted losses are significant. While global famines are now relatively rare, some 50 million people suffer from “hidden hunger” — nutrient-deficient diets that are masked by being otherwise calorie-sufficient.

For animal-derived nutrients such as B12 and omega-3 fatty acids, nearly 20 per cent of the global population are at risk of becoming nutrient-deficient in coming decades due to reliance on wild-caught fish.

Climate change is also affecting natural cycles of nutrients in the ocean. For example, it has been predicted that increasing water temperatures will cause a decline in natural omega-3 availability from seafood by more than 50 per cent by 2100. At the bottom of the food chain, microalgae that naturally produce omega-3s are less productive at warmer temperatures and this cascades through marine and freshwater food chains resulting in fish having less omega-3s available to eat and store in their bodies.

These kinds of climate-caused losses are expected to disproportionately affect vulnerable populations, especially in inland Africa.

Challenges and strategies for nutritious seafood

Aquaculture can help supply some of these missing nutrients, but it is an industry also vulnerable to the effects of climate change. A recent study predicted that 90 per cent of aquaculture will be impacted by climate change, where warm waters increase disease outbreaks, harmful algal blooms and impact the availability of feed supplies.

Global disparities already exist in food security that will be exacerbated by climate change in the future. Yet the effects of warming waters on nutrient availability from seafood will compound these inequities among tropical and low-income countries.

These results suggest a major challenge to our future nutritional security that demands strong fisheries and aquaculture management to facilitate equitable distribution of nutritious seafoods.

Improvements are possible.

For example, redirecting nine per cent of Namibia’s fisheries toward its coastal population would alleviate the severe iron deficiencies experienced there. Policies that prioritize nutrient supply would help maintain diets as the climate warms.

The recent United Nations call to action for blue transformation emphasizes the need to provide sufficient aquatic food from fisheries and aquaculture for our growing population in a sustainable way.

To do this, strategies are needed to achieve healthy, equitable and resilient food systems that adequately deal with overfishing, strive for equal access to resources and markets and mitigate the environmental impacts of aquatic food production.

Ultimately, these strategies must support the nutritional security of vulnerable nations and consider global health equity and the cultural significance of seafood.

Stefanie Colombo, Canada Research Chair in Aquaculture Nutrition, Dalhousie University and Aaron MacNeil, Professor, Department of Biology, Dalhousie University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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