COP26 is the 2021 United Nations climate change conference
For nearly three decades the UN has been bringing together almost every country on earth for global climate summits – called COPs – which stands for ‘Conference of the Parties’. In that time climate change has gone from being a fringe issue to a global priority. Specifically part of the COP conference is focused on our oceans and seas. Part of the COP discussions includes the ‘Ocean Decade’.
What is the Ocean Decade?
The Ocean Decade provides a ‘once-in a-lifetime’ opportunity to create a new foundation across the science-policy interface to strengthen the management of the ocean and coasts for the benefit of humanity and to mitigate the impacts of climate change. The Ocean Decade Implementation Plan outlines ten Decade Challenges, representing the most immediate and pressing needs of the Decade.
Marine plankton breathe more than 20 million tons of sulfur into the air every year, mostly in the form of dimethyl sulfide (DMS). In the air, this chemical can transform into sulfuric acid, which helps produce clouds by giving a site for water droplets to form. Over the scale of the world’s oceans, this process affects the entire climate.
But new research from the University of Wisconsin–Madison, the National Oceanic and Atmospheric Administration and others reveals that more than one-third of the DMS emitted from the sea can never help new clouds form because it is lost to the clouds themselves. The new findings significantly alter the prevailing understanding of how marine life influences clouds and may change the way scientists predict how cloud formation responds to changes in the oceans.
By reflecting sunlight back into space and controlling rainfall, clouds play significant roles in the global climate. Accurately predicting them is essential to understanding the effects of climate change.
New fisheries management planning tool developed with fewer stocks expected
The future of cod stocks in the North Sea and the Barents Sea may be much easier to predict than before. This is the result of an international research project led by the Helmholtz-Zentrum Hereon and its Institute of Coastal Systems – Analysis and Modeling. For the first time, the team has succeeded in predicting the development of stocks for ten years in advance, taking into account both changes due to climate and fishing. Traditionally, fisheries experts provide catch recommendations for about a year in advance, on the basis of which fishing quotas are negotiated and set internationally. This involves first estimating the size of current cod stocks and then calculating how much cod can be caught in the coming year without endangering the stocks as well as harvesting the stock optimally. The climatic change, long-term changes in water temperature, circulation and mixing, which have a decisive influence on how well cod reproduce, are not included in this prediction, so that the development of stocks can only be predicted in the short term.
Warm North Sea causes stress
As the experts around climate modeler Vimal Koul und Corinna Schrum of Hereon now write in the journal Nature Communications Earth and Environment, they have taken temperature into account in their calculations. For the North Sea, the climate forecast continues to predict temperatures at a high level, so that cod stocks are unlikely to recover or reach earlier levels. As a result, catches are expected to remain low. Things look better for the Barents Sea, where stocks can be managed sustainably.
For the researchers, the challenge was that climate models cannot calculate how much fish there will be in the oceans in the future. They only provide information about expected temperatures. “So we first had to develop a program that translates water temperature into fish quantities,” says Vimal Koul. Among other things, this took into account the ocean temperature in the North Atlantic. The researchers were then able to run their prediction model. The model starts with today’s conditions – the current temperature conditions and the current carbon dioxide content of the atmosphere, and can then calculate how the situation will change as carbon dioxide concentrations increase. The future temperatures are then translated into expected fish abundance and stock sizes.
To test how reliably the model works, it was first compared with real fish data from the 1960s to the present. As it turned out, it was able to correctly estimate fish stocks for the ten-year periods since the early 1960s. In this respect, the researchers led by Vimal Koul can assume that the current view of the coming ten years is also correct.
Fishing intensity taken into account
Another interesting aspect of the study is that the team of climate modelers, fisheries biologists and oceanographers took four different fishing scenarios into account. This allowed them to determine how cod stocks would fare if they were fished at different levels – from intensive to sustainable. In this respect, the results of the current study are very practical. “The 10-year estimates will help the fishing industry better plan catches in the future – so that cod stocks are fished sustainably and gently despite changes in climate,” says Vimal Koul. The new 10-year calculation model could also help fishing companies in their strategic planning – by providing a secure basis for investments in new vessels or processing facilities.
More information: Koul, V., Sguotti, C., Årthun, M. et al. Skilful prediction of cod stocks in the North and Barents Sea a decade in advance. Commun Earth Environ2, 140 (2021). https://doi.org/10.1038/s43247-021-00207-6
Unprecedented changes in climate and biodiversity, driven by human activities, have combined and increasingly threaten nature, human lives, livelihoods and well-being around the world. Biodiversity loss and climate change are both driven by human economic activities and mutually reinforce each other. Neither will be successfully resolved unless both are tackled together.
This is the message of a new IPES/IPCC report, published by 50 of the world’s leading biodiversity and climate experts. This is the first time that the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) and the Intergovernmental Panel on Climate Change (IPCC) – two intergovernmental bodies have collaborated together.
The report finds that previous policies have largely tackled biodiversity loss and climate change independently of each other, and that addressing the synergies between mitigating biodiversity loss and climate change, while considering their social impacts, offers the opportunity to maximize benefits and meet global development goals.
Among the most important available actions identified in the report are:
Stopping the loss and degradation of carbon- and species-rich ecosystems on land and in the ocean, especially forests, wetlands, peatlands, grasslands and savannahs; coastal ecosystems such as mangroves, salt marshes, kelp forests and seagrass meadows; as well as deep water and polar blue carbon habitats. The report highlights that reducing deforestation and forest degradation can contribute to lowering human-caused greenhouse gas emissions, by a wide range from 0.4-5.8 gigatonnes of carbon dioxide equivalent every year.
North Atlantic warming over six decades drives decreases in krill abundance with no associated range shift
A team of UK and French scientists have shown a huge decline in North Atlantic krill over the last 60 years driven primarily by climate variability and North Atlantic warming. Krill, are extremely abundant crustaceans present throughout the world’s oceans. In the North Atlantic, krill are numerically a significant component of the biomass of marine ecosystems particularly in the more boreal and Arctic waters of the North Atlantic. They are an important source of food for commercially exploited fish species, squid and marine mammals such as baleen whales and therefore represent a crucial component in North Atlantic food webs.
50% decline in krill abundance
Examining the data that used long-term observations of krill, the team led by Martin Edwards from Plymouth Marine Laboratory (PML) showed that across the whole North Atlantic basin there has been a 50% decline in krill abundance over the last 60 years. The findings, published in the journal Communications Biology https://www.nature.com/articles/s42003-021-02159-1show this widespread and abrupt decline has been associated with the warming climate of the North Atlantic observed over the last six decades. This warming has particularly accelerated since the mid 1990s where there was an abrupt shift to warmer conditions in Atlantic waters.
Accelerated pace of changes in the Arctic
In the sub-polar regions of the North Atlantic, where krill are most abundant, concern is growing at the accelerated pace of these changes and the increasing ‘Atlantification’ (i.e warmer more saline Atlantic waters) of these more northern waters and their detrimental effects on Arctic systems. The Arctic sea regions, in particular, are experiencing the strongest warming on the planet (nearly three times as fast as the planetary average) and the loss of sea ice in recent decades has been very rapid. Many regional seas that were once considered as being inhabited exclusively by Arctic flora and fauna have become more influenced by more southerly species as these species move northward as the Arctic warms.
Martin Edwards said ‘as ocean temperature rise, we generally expect species distributions to track towards historically cooler regions in line with their preferred habitats. In this case we would expect the krill populations to simply shift northward to avoid the warming environment and find new habitats in cooler regions of the North Atlantic. However, this study shows for the first time in the North Atlantic that marine populations do not simply just shift their distributions northward due to shifting isotherms to re-establish new geographic habitats’.
Angus Atkinson also from PML said ‘while krill has declined in abundance by 50%, its core latitudinal distribution at ~55 oN has remained markedly stable over the 60 year period’. The study showed that the isotherms for the warmer temperatures are shifting steadily northwards, the cooler isotherms remain in place with an 8 degree difference in average latitudes of the 7-8°C and 12-13°C isotherms in 1958-1967 but only 4 degrees of latitude between the same temperatures in 2008-2017. This ‘habitat squeeze’ and a potential habitat loss of 4 degrees of latitude could be the main driver in the decline of krill populations seen in this study. This highlights that, as the temperature warms, not all species will be able to tract isotherms as they shift northward and there will be particular species that will win or lose when establishing new habitats as more northerly regions like the Barents Sea and Arctic Ocean become increasingly warmer and ‘Atlantified’.
One of the main reasons for the lack of northerly movement is because the centre of krill populations is found in the North West Atlantic (south and east of Greenland) and populations can become spatially constrained due to ocean currents and strong thermal boundaries such as the polar front limiting their northward expansions. Here, unlike the North East Atlantic which has unimpeded northward flow into the Norwegian and Barents Seas, this region is latitudinally stalled by the sub-polar gyre circulation which is geographically and temporally more robust and forms a thermal barrier to the rapid northward expansion of species.
Martin Edwards further added: ‘while temperature alone does not necessary explain all patterns observed in this study, as trophic interactions would also play an important role, we are currently exploring the mechanisms for these wide-scale changes. We also do not currently know the full ecological ramifications of this dramatic decline in krill but they would presumably have had major consequences for the rest of the marine food-web and will have important implications for ongoing fisheries in the North Atlantic’.
Edwards, M., Goberville, E., Helaouet, P., Lindley, A., Atkinson, A., Burrows, M., Tarling, G. (2021). North Atlantic warming over six decades drives decreases in krill abundance with no associated range shift. Commun Biol4, 644. https://doi.org/10.1038/s42003-021-02159-1
The Arctic has warmed three times more quickly than the planet as a whole, and faster than previously thought according to the newly published ‘Arctic Climate Change update 2021’.
Arctic sea ice looks set to be an early victims of rising temperatures, with each fraction of a degree making a big difference: the chance of it disappearing entirely in summer is 10 times greater if Earth warms by 2 degrees Celsius above pre-industrial levels compared to 1.5C, the goal set by the 2015 Paris Accord.
The finding comes from the Arctic Monitoring and Assessment Programme (AMAP) in their new report.
In less than half a century, from 1971 to 2019, the Arctic’s average annual temperature rose by 3.1C, compared to 1C for the planet as a whole.
That’s more than previously suspected. In a 2019 report on Earth’s frozen spaces, the UN’s Intergovernmental Panel on Climate Change (IPCC) concluded that Arctic surface air temperature has likely increased “by more than double the global average”.
According to researchers, a turning point came in 2004 when the temperature in the Arctic surged for largely unexplained reason.
Since then, warming has continued at a rate 30 percent higher than in previous decades.
Warming has immediate consequences for the Arctic ecosystem, including changes in habitat, food habits and interactions between animals and the migration of some species.
The warming and freshening of the Arctic Ocean directly and indirectly affect the lifecycles of marine species, leading to changes in seasonality, range shifts, and broad changes in ocean ecosystems.
The decline in sea ice affects marine ecosystems through changes in the open water areas and increases in the length of the open water period (both of which affect phytoplankton and ice algae, including the timing of phytoplankton blooms), as well as under-ice productivity and diversity. These changes are having cascading effects through ecosystems, with widespread impacts on the distribution, seasonality, and abundance of a variety of species.
Satellite data show an increasing trend in primary production in all regions of the Arctic Ocean over the past two decades, explained by complex changes in light and nutrient conditions. The consequences of warming near the ocean surface on primary producers in the surface and subsurface ocean layers are still poorly understood, and there is new evidence that dominant Arctic phytoplankton species may be able to adapt to higher temperatures.
Changes in the Arctic Ocean gateways
Warmer waters from the Pacific and Atlantic are also pushing farther into the Arctic Ocean, with widespread impacts on ocean ecosystems. The composition of Arctic plankton communities that form the basis of marine food webs is changing, as are the distribution and abundance of a variety of invertebrate, fish, and marine mammal species.
As the sea ice shrinks in the Arctic, the plankton community that produces food for the entire marine food chain is changing. New research shows that a potentially toxic species of plankton algae that lives both by doing photosynthesis and absorbing food may become an important player in the Arctic Ocean as the future sea ice becomes thinner and thinner.
Microscopic plankton algae, invisible to the naked eye, are the foundation of the marine food web, feeding all the ocean´s living creatures from small crustaceans to large whales. Plankton algae need light and nutrients to produce food by photosynthesis.
A thick layer of sea ice – sometimes covered with snow – can reduce how much sunlight penetrates into the water and stop the algae getting enough light. However, as the sea ice is becoming thinner and less widespread in the Arctic, more and more light is penetrating into the sea. Does this mean more plankton algae and thus more food for more fish, whales and seabirds in the Arctic? The story is not so simple.
More light in the sea will only lead to a higher production of plankton algae if they also have enough nutrients – and this is often not the case. With the recent increase in freshwater melt from Arctic glaciers and the general freshening of the Arctic Ocean, more and more fresh and nutrient-depleted water is running out into the fjords and further out into the sea. The fresher water lies on top of the more salty ocean and stops nutrients from the deeper layers from mixing up towards the surface where there is light. And it is only here that plankton algae can be active.
Mixotrophic algae play on several strings
However, a new study published in the journal Nature – Scientific Reports shows that so-called mixotrophic plankton algae may play a crucial role in the production of food in the Arctic Sea.
Mixotrophic algae are small, single-celled plankton algae that can perform photosynthesis but also obtain energy by eating other algae and bacteria. This allows them to stay alive and grow even when their photosynthesis does not have enough light and nutrients in the water.
In northeast Greenland, a team of researchers measured the production of plankton algae under the sea ice in the high-Arctic fjord Young Sound, located near Daneborg.
“We showed that the plankton algae under the sea ice actually produced up to half of the total annual plankton production in the fjord,” says Dorte H. Søgaard from the Greenland Climate Research Centre, Greenland Institute of Natural Resources and the Arctic Research Centre, Aarhus University, who headed the study.
“Mixotrophic plankton algae have the advantage that they can sustain themselves by eating other algae and bacteria as a supplement to photosynthesis when there isn’t enough light. This means that they are ready to perform photosynthesis even when very little light penetrates into the sea. In addition, many mixotrophic algae can live in relatively fresh water and at very low concentrations of nutrients – conditions that often prevail in the water layers under the sea ice in the spring when the ice melts,” Dorte H. Søgaard explains.
Toxic algae kill fish
For nine days, the researchers measured an algal bloom driven by mixotrophic algae occurring under the thick but melting sea ice in Young Sound during the Arctic spring in July, as the sun gained more power and more melt ponds spread across the sea ice, gradually letting through more light.
The algae belong to a group called haptophytes. Many of these algae are toxic, and in this study they bloomed in quantities similar to those previously observed in the Skagerrak near southern Norway. Here, the toxic plankton algae killed large amounts of salmon in Norwegian fish farms.
“We know that haptophytes often appear in areas with low salinity – as seen in the Baltic Sea, for example. It is therefore very probable that these mixotrophic-driven algae blooms will appear more frequently in a more freshwater-influenced future Arctic Ocean and that this shift in dominant algae to a mixotrophic algae species might have a large ecological and socio-economic impact.” says Dorte H. Søgaard.
The researchers behind the project point out that it is the first time that a bloom of mixotrophic algae has been recorded under the sea ice in the Arctic.
Freshwater is accumulating in the Arctic Ocean. The Beaufort Sea, which is the largest Arctic Ocean freshwater reservoir, has increased its freshwater content by 40% over the past two decades. How and where this water will flow into the Atlantic Ocean is important for local and global ocean conditions.
A new study shows that this freshwater travels through the Canadian Archipelago to reach the Labrador Sea, rather than through the wider marine passageways that connect to seas in Northern Europe. The open-access study was published in Nature Communications.
“The Canadian Archipelago is a major conduit between the Arctic and the North Atlantic,” said lead author Jiaxu Zhang, a UW postdoctoral researcher at the Cooperative Institute for Climate, Ocean and Ecosystem Studies. “In the future, if the winds get weaker and the freshwater gets released, there is a potential for this high amount of water to have a big influence in the Labrador Sea region.”
The finding has implications for the Labrador Sea marine environment, since Arctic water tends to be fresher but also rich in nutrients. This pathway also affects larger oceanic currents, namely a conveyor-belt circulation in the Atlantic Ocean in which colder, heavier water sinks in the North Atlantic and comes back along the surface as the Gulf Stream. Fresher, lighter water entering the Labrador Sea could slow that overturning circulation.
“We know that the Arctic Ocean has one of the biggest climate change signals,” said co-author Wei Cheng at the UW-based Cooperative Institute for Climate, Ocean and Atmosphere Studies. “Right now this freshwater is still trapped in the Arctic. But once it gets out, it can have a very large impact.”
Fresher water reaches the Arctic Ocean through rain, snow, rivers, inflows from the relatively fresher Pacific Ocean, as well as the recent melting of Arctic Ocean sea ice. Fresher, lighter water floats at the top, and clockwise winds in the Beaufort Sea push that lighter water together to create a dome.
When those winds relax, the dome will flatten and the freshwater gets released into the North Atlantic.
“People have already spent a lot of time studying why the Beaufort Sea freshwater has gotten so high in the past few decades,” said Zhang, who began the work at Los Alamos National Laboratory. “But they rarely care where the freshwater goes, and we think that’s a much more important problem.”
Using a technique Zhang developed to track ocean salinity, the researchers simulated the ocean circulation and followed the Beaufort Sea freshwater’s spread in a past event that occurred from 1983 to 1995.
Their experiment showed that most of the freshwater reached the Labrador Sea through the Canadian Archipelago, a complex set of narrow passages between Canada and Greenland. This region is poorly studied and was thought to be less important for freshwater flow than the much wider Fram Strait, which connects to the Northern European seas.
In the model, the 1983-1995 freshwater release traveled mostly along the North American route and significantly reduced the salinities in the Labrador Sea — a freshening of 0.2 parts per thousand on its shallower western edge, off the coast of Newfoundland and Labrador, and of 0.4 parts per thousand inside the Labrador Current.
The volume of freshwater now in the Beaufort Sea is about twice the size of the case studied, at more than 23,300 cubic kilometers, or more than 5,500 cubic miles. This volume of freshwater released into the North Atlantic could have significant effects. The exact impact is unknown. The study focused on past events, and current research is looking at where today’s freshwater buildup might end up and what changes it could trigger.
“A freshwater release of this size into the subpolar North Atlantic could impact a critical circulation pattern, called the Atlantic Meridional Overturning Circulation, which has a significant influence on Northern Hemisphere climate,” said co-author Wilbert Weijer at Los Alamos National Lab.
The ocean is dynamic in nature, playing a crucial role as a planetary thermostat that buffer global warming. However, in response to climate change, the ocean has generally become stabler over the past 50 years. Six times stabler, in fact, than previously estimated–as shown by a new study that researchers from the CNRS, Sorbonne University, and IFREMER have conducted within the scope of an international collaboration.* Warming waters, melting glaciers, and disrupted precipitation patterns have created an ocean surface layer cut off from the depths. Just as oil and water separate, so this division of surface and deeper waters limits oceanic mixing, making it harder for the ocean to mitigate climate change. Furthermore, climate change has strengthened winds, which has thickened the ocean surface layer by 5 to 10 m per decade over the last half century. This has hindered vital access to light for most marine organisms within it. Published in Nature, these findings underscore the consequences of climate change and anthropogenic phenomena for the ocean, the life it harbours, and its capacity to remain a global thermostat into the future.
This work calls for reconsideration of the drivers of ongoing shifts in marine primary production, and reveals stark changes in the world’s upper ocean over the past five decades.
More information: Sallée, JB., Pellichero, V., Akhoudas, C. et al. Summertime increases in upper-ocean stratification and mixed-layer depth. Nature591, 592–598 (2021). https://doi.org/10.1038/s41586-021-03303-x
They are diligently stoking thousands of bonfires on the ground close to their crops, but the French winemakers are fighting a losing battle. An above-average warm spell at the end of March has been followed by days of extreme frost, destroying the vines with losses amounting to 90 percent above average. The image of the struggle may well be the most depressingly beautiful illustration of the complexities and unpredictability of global climate warming. It is also an agricultural disaster from Bordeaux to Champagne.
It is the loss of the Arctic sea-ice due to climate warming that has, somewhat paradoxically, been implicated with severe cold and snowy mid-latitude winters.
“Climate change doesn’t always manifest in the most obvious ways. It’s easy to extrapolate models to show that winters are getting warmer and to forecast a virtually snow-free future in Europe, but our most recent study shows that is too simplistic. We should beware of making broad sweeping statements about the impacts of climate change.” Says professor Alun Hubbard from CAGE Center for Arctic Gas Hydrate, Environment and Climate at UiT The Arctic University of Norway.
Melting Arctic sea ice supplied 88% of the fresh snow
Hubbard is the co-author of a study in Nature Geoscience examining this counter-intuitive climatic paradox: A 50% reduction in Arctic sea-ice cover has increased open-water and winter evaporation to fuel more extreme snowfall further south across Europe.
The study, led by Dr. Hanna Bailey at the University of Oulu, Finland, has more specifically found that the long-term decline of Arctic sea-ice since the late 1970s hada direct comparison to one specific weather event: “Beast from the East”—the February snowfall that brought large parts of the European continent to a halt in 2018, causing £1bn a day in losses.
Researchers discovered that atmospheric vapor traveling south from the Arctic carried a unique geochemical fingerprint, revealing that its source was the warm, open-water surface of the Barents Sea, part of the Arctic Ocean between Norway, Russia, and Svalbard. They found that during the “Beast from the East,” open-water conditions in the Barents Sea supplied up to 88% of the corresponding fresh snow that fell over Europe.
Climate warming is lifting the lid off the Arctic Ocean
“What we’re finding is that sea-ice is effectively a lid on the ocean. And with its long-term reduction across the Arctic, we’re seeing increasing amounts of moisture enter the atmosphere during winter, which directly impacts our weather further south, causing extreme heavy snowfalls. It might seem counter-intuitive, but nature is complex and what happens in the Arctic doesn’t stay in the Arctic.” says Bailey.
When analyzing the long-term trends from 1979 onwards, researchers found that for every square meter of winter sea-ice lost from the Barents Sea, there was a corresponding 70 kg increase in the evaporation, moisture, and snow falling over Europe.
“This study illustrates that the abrupt changes being witnessed across the Arctic now, really are affecting the entire planet,” says professor Hubbard.
Their findings indicate that within the next 60 years, a predicted ice-free Barents Sea will likely become a significant source of increased winter precipitation—be it rain or snow—for Europe.
More information: Hannah Bailey et al, Arctic sea-ice loss fuels extreme European snowfall, Nature Geoscience (2021). DOI: 10.1038/s41561-021-00719-y