Aquatic publication review (31)

Climate change is increasingly affecting all ecosystems on Earth, from permafrost to the Arctic to marine and tropical ecosystems and human communities. Recent scientific studies show that warming processes and their effects are accelerating, causing unforeseen effects such as an increase in the risk of deaths among young people, degradation of permafrost, an ice-free Arctic and changes in ocean food webs.

1. the first ice-free day in the Arctic Ocean could occur before 2030

Li Y., Zhang H., Kumar P. et al. (2024). The first ice-free day in the Arctic Ocean could occur before 2030.Nat Commun 15, 10101.

For decades, scientists have been warning about the impact of climate change on the Arctic, and the vision of an Arctic Ocean devoid of ice in summer is becoming increasingly real. A new study, based on CMIP6 climate models, makes a fairly accurate prediction. The study indicates that the first ice-free day in Antarctica could occur as early as within the next few years, with a non-zero probability of occurring before 2030.

The research was carried out by an international team of scientists, who used daily data from CMIP6 climate models covering various greenhouse gas (SSP) emission scenarios. The simulations were based on assumptions about the state of sea ice in 2023, when the minimum daily area was 3.39 million km². The team analyzed a total of 366 simulations from 11 models, taking into account both internal climate variability and different socioeconomic development pathways.

The researchers found that the first day when the Arctic Ocean will be completely ice-free could occur as early as within the next three years, counting from conditions in 2023, which means that the phenomenon could occur even before 2030. This is a very pessimistic plan. In other scenarios, taking into account different baseline data, the timeframe for the appearance of an ice-free day in the Antarctic Sea is in the range of 7-20 years.

The greatest threat to the presence of ice in the Arctic Sea is extreme weather, such as the influx of warm air in winter, spring blockades and summer storms. Analyses have shown that such events are becoming more frequent in a warming Arctic.

2. enhanced warming of European mountain permafrost in the early 21st century

Jones P., Müller R., Santiago P. et al. (2024). Enhanced warming of European mountain permafrost in the early 21st century. Nat Commun 15, 10508.

Warming of Europe’s mountain permafrost, a key component of the cryosphere, has accelerated significantly in the 21st century. The results of the latest study, based on decadal data from 64 boreholes in the Alps, Scandinavia, Iceland, the Sierra Nevada and Svalbard, confirm that between 2013 and 2022, the rate of temperature increase at a depth of 10 meters exceeded 1°C per decade. This is significantly higher than previous estimates.

Temperatures rose fastest in cold, ice-poor land at high altitudes and latitudes, such as Svalbard and the Western Alps. Ice-rich land close to the melting point showed a slower rate of change due to the latent heat effect. It masks temperature fluctuations until the ice has completely melted. Significantly, over the past decade, permafrost has completely disappeared in 17 percent of the locations surveyed at a depth of 10 meters.

The analysis showed that the warming process of the mountain permafrost in Europe is proceeding at different intensities depending on the season. In recent years, higher summer and autumn temperatures have had the greatest impact. In the long term, however, warmer winters are key.

Scientists stress the urgent need for long-term monitoring, especially in under-researched regions such as the Pyrenees, the Carpathians and the highest parts of the Alps. The continuation of these studies is crucial for assessing the impact of climate change and developing adaptation strategies.

3. high heat is preferentially killing the young, not the old, new research finds

Shrader J., Bressler R. D., Wilson A. et al. (2024). High heat is preferentially killing the young, not the old, new research finds. Science Advances.

Previous analyses have indicated that the elderly are most at risk of dying from extreme heat in the context of a warming climate. However, a new study, conducted in Mexico, turns this view upside down, revealing that as many as 75 percent of heat-related deaths involve people under the age of 35, with those aged 18 to 35 accounting for the largest percentage. These results are all the more surprising given that young people are considered the most resilient group in the population.

The study was conducted by an international team of scientists, including researchers from Columbia Climate School and Stanford University. The team used detailed mortality and daily temperature data from Mexico, covering the period 1998-2019. The analysis involved correlating high mortality – the number of deaths above average – with temperatures measured on the wet thermometer scale, which takes into account the effects of heat and humidity.

An average of about 3,300 heat-related deaths per year have been reported in Mexico. Nearly a third of these involved people between the ages of 18 and 35, a disproportionately high number in relation to this group’s share of the population. Infants and children under the age of 5 were also in the high-risk group. In contrast, people aged 50-70 rarely died as a result of high temperatures.

The researchers note that young people are particularly vulnerable to the effects of hot weather due to the type of work they do, mostly physical, often in harsh conditions without access to air conditioning. This includes farming, construction and working in enclosed, poorly ventilated spaces. In addition, they are the ones who are more likely to engage in strenuous outdoor physical activities, such as playing sports, which increases the risk of dehydration and heat stroke.

The study’s findings indicate that young people are more vulnerable to the effects of heat than previously assumed, with important global implications. In middle- and low-income countries, where they perform physical labor in harsh conditions, heat-related mortality may be even higher.

The researchers also noted that in Mexico, the elderly were more likely to die from moderate cold rather than heat, which is linked to their susceptibility to infections indoors. Nonetheless, global warming has caused an increase in the percentage of heat-related deaths since the beginning of the 21st century, a trend that is expected to increase.

4. how do marine food webs respond to increasing alkalinity?

Johansson L., Pacheco F., Smith J. et al. (2024). How do marine food webs respond to increasing alkalinity? Science Advances.

Increasing the alkalinity of the oceans can play a key role in the fight against climate change, enabling greater carbon dioxide uptake and counteracting water acidification. The OAE (Ocean Alkalinity Enhancement) method, which involves adding soluble minerals such as sodium carbonate or bicarbonate to seawater, increases the ocean’s ability to fix_CO2. However, the process can lead to increased water pH, raising questions about its potential impact on aquatic organisms and the stability of food webs.

Although initial studies indicate that moderate alkalinity changes have minimal impact on zooplankton and do not disrupt food chains, the researchers stress the need for further analysis. In particular, it is important to study how the method will affect diverse marine ecosystems and whether long-term chemical changes will harm sensitive species.

Zooplankton showed high tolerance to chemical changes in the water, and the nutritional quality of the organic particles had no significant effect on consumers. The experiment was conducted in oligotrophic subtropical waters, which may have limited the possible responses of zooplankton to chemical changes.

The study used KOSMOS (Kiel Off-Shore Mesocosms for Ocean Simulations) mesocosms, which are large tubes, isolating a column of water of 8^m3, submerged in seawater. The experiment was conducted off the coast of Gran Canaria. Different concentrations of sodium carbonate and bicarbonate were added to the tubes to obtain varying OAE values. Zooplankton responses to the chemical changes were monitored, analyzing biomass, diversity and fatty acid content, among others, for 33 days. OAE could become an important tool in the fight against global warming, enhancing the ocean’s ability to absorb_CO2 and reduce its acidification.

The study indicates that with moderate changes in alkalinity, the impact on zooplankton is minimal, making the method a promising option for climate protection efforts. Although the results of the experiment are optimistic, the researchers stress the need for further analysis, especially in other marine environments and using different OAE techniques.