The experts use mathematical models (1) to understand how climate change could affect mean sea level rise. These models are based on historical data from studies that reconstructed the paleoclimate (2) environment, data of ocean warming, ocean expansion and gas emissions to the atmosphere.

These models can be used to project different model scenarios regarding changes in mean sea level rise over time, considering more conservative and more extreme climate change scenarios. The reference scientific panel that regularly evaluates the impacts and ways to adapt to climate change is the Intergovernmental Panel on Climate Change (IPCC). The IPCC is also responsible for modeling climate change impacts on sea level rise, with models that span from 1850 to 2017.

The IPCC most extreme scenario of mean sea level rise considers a rise of 1.1 m until 2100, while the most conservative predicts a rise of 0.45 m. Yet, scientists from Denmark and Norway recently proposed a different scenario, which presents an increase in sea level rise higher than 1.1 m after 2100 based on historical data of global sea level rise and the average temperature of our planet. This model shows an almost linear relationship between global mean surface temperature and the average rate of the sea level rise in the next century. In the Antarctic region, the sea level is projected to rise at the same scale as the mean global surface temperature.

Most studies on the impacts of climate change on mean sea level rise are based on the IPCC most conservative model scenario. Nevertheless, the newly proposed model scenario suggests that the IPCC extreme scenario could actually be closer to reality.

(1) Mathematical Models- A mathematical model is a simplified representation or interpretation of the reality. (2) Paleoclimate- Science that studies the past of the earth’s climate before the availability of instrumental records.

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Source: Aslak Grinsted and Jens Hesselbjerg Christensen (2021). The transient sensitivity of sea level rise. Ocean Sci., 17, 181–186, 2021. doi: 10.5194/os-17-181-2021

Author: Ana Filipa Fernandes

When species co-occur in a certain habitat and use similar food resources, competition can take place. In this context, we refer to the concept of ‘ecological niche’, i.e. the multidimensional space defined by what organisms feed on and the habitat they occupy. The degree of niche similarity can help understanding the potential for competition among organisms, especially when resources are scarce. Cephalopods (e.g. squids and octopus) are overall understudied, despite their important role both as prey and predators in marine food webs. Under pressing climate and environmental changes, which are intensified in Arctic regions, it is important to better understand the role of cephalopods in the food web.

A team of researchers, including the Portuguese Dr. Filipe Ceia and Dr. José Xavier, recently published a study in Nature analyzing the potential for competition among the three Arctic bobtail squids Rossia palpebrosa, R. magaptera and R. moelleri. The species were collected in the Kara Sea, Barents Sea and Greenland from 2003-2019, depending on the region. Researchers used the food web markers carbon (δ13C) and nitrogen (δ15N) stable isotopes to infer diet and niche ecology. Levels of these isotopes can be measured in animal tissue and indicate the feeding sources (δ13C; e.g. feeding on bottom vs feeding on the water column) and trophic position (δ15N; role in the food web, e.g. primary, secondary consumer).

The three species co-occur, have similar body size and feed near the bottom of the ocean, mostly on crustaceans, marine worms and fish. So how do they partition their habitat to avoid competition? Here is how:

a) R. moelleri inhabit the water column more often;

b) R. megaptera and R. moelleri migrate, while R. palpebrosa may be more sedentary;

c) R. megaptera and R. moelleri show more distinct differences in body size between males and females, and females tend to occupy a larger ecological niche than males (i.e. females are less picky with their food);

d) Diets of R. megaptera and R. moelleri change less regionally compared to R. palpebrosa;

e) R. megaptera and R. palpebrosa eat more crustaceans, while R. moelleri eats more fish;

f) The diet of R. palpebrosa and R. moelleri becomes more specialized (a.k.a. pickier with their food) as they grow up, while the diet of R. megaptera becomes less specialized;

g) R. palpebrosa and R. moelleri use similar ways to reduce competition within each species, different from R. megaptera, that is the first two species favor smaller individuals and the niches of different size classes largely overlap, while R. megaptera favors larger individuals.

Given that none of these traits was shared among the three species, all traits together form a pattern in which each species ends up with a unique strategy of resource and habitat use.

And what about the impacts of climate change in these species? R. palpebrosa and R. moelleri will likely not be affected since the first has a more flexible niche and thermal tolerance and is currently the most widespread of the three species in the Arctic, and the second is an Arctic-adapted species. For R. magaptera, since this species inhabits warmer waters, climate change will likely create better conditions for niche expansion in the Barents Sea and strengthen their advantage in West Greenland.

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Source: Golikov A V, Ceia FR, Sabirov RM, Batalin GA, Blicher ME, Gareev BI, Gudmundsson G, Jørgensen LL, Mingazov GZ, Zakharov D V, et al. 2020. Diet and life history reduce interspecific and intraspecific competition among three sympatric Arctic cephalopods. Sci Rep. 10:21506. doi: 10.1038/s41598-020-78645-z.

Author: Sara Pedro

When we speak about pollution in the Poles, geographically isolated locations, we normally talk about atmospheric or aquatic transportation, or natural sources such as volcanoes. However, there are other ways in which these contaminants can get to the Antarctic continent.

The truth is that seabirds also have their part in bringing several types of contaminants to these isolated locations. Why? Seabirds gather in large groups, called colonies, which results in a big amount of feces being deposited in the soil in the same place. A recent study came to the conclusion that several contaminants, and not only nutrients, accumulate in these birds and are released into the environment through their feces.

This way, to verify which contaminants are being released by these animals, a group of scientists from Brazil and France went to Antarctica and took soil samples from colonies and samples from soils far away from these colonies. When comparing the results from these two types of soils, they concluded that the soils from the colonies have higher concentrations of a few contaminants such as Cadmium (Cd), Mercury (Hg), Arsenic (As) and others.

However, there are many other sources of these elements, and so it is necessary to confirm that these are in fact being released by seabirds, before we can say for sure that seabirds are a source of pollution in the Poles. So, the study used the analysis of stable isotopes of carbon (C) and nitrogen (N) that due to their high resolution can distinguish the different sources. For example, locations with higher amounts of feces showed a high percentage of fractionation of the N15 isotope, with values corresponding to animal-derived nitrogen. Being able to conclude that in fact, there was a large amount of contaminants associated with seabird feces.

Although it seems that seabirds are a source of pollution in Antarctica (which has also been observed in the Arctic), there is still a lot to study! The type of birds, the size of colonies, the health of the birds and many other factors can influence these results!

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Source: C.V.Z. Cipro, P. Bustamante, M.V. Petry, R.C. Montone, Seabird colonies as relevant sources of pollutants in Antarctic ecosystems: Part 1 – Trace elements, Chemosphere, Volume 204, 2018, Pages 535-547. DOI: 10.1016/j.chemosphere.2018.02.048

Author: Beatriz Bento

These pollutants, whose atmospheric concentrations have declined since the beginning of the lockdown, are short-lived, that is, they stay in the atmosphere for a short period of time and influence the local weather in a city or urban area where they are released. Once in the atmosphere, NOx contribute to acid rain and the formation of ground-level ozone. This type of ozone should not be confused with the ozone layer in the stratosphere that protects us against UV radiation. In lower regions of the atmosphere, ozone is a highly oxidative gas that can react with other particles forming a toxic cloud known as smog.

Particles in suspension in the atmosphere, such as dust, soot and volatile compounds, are small, less than PM10 or even PM2.5 (i.e. particles of less than 10 or 2.5 micrometers per cubic meter) and consequently can be inhaled through the respiratory system. According to State of Flobal Air 2018, more than four million deaths per year at a global scale are related to respiratory issues associated with these particles.

What about carbon dioxide CO2?

In contrast with short-lived pollutants, CO2, methane CH4 and nitrous oxide N2O can remain in the atmosphere for decades or more. Approximately 2.4 trillions of tones of CO2 were released to the atmosphere between 1850 and 2019, after the industrial revolution. Of these, 40% accumulated in the atmosphere and the remaining 60% were sequestrated in the oceans and by biosphere. According to Carbon Brief, just the year of 2019 corresponded to 45 Gton of CO2 releases.

What can we expect from 2020 taking into account COVID 19 lockdown?

Not a large difference from previous years regarding CO2. Instead of the predicted 43 Gton, this year the releases will be around 40 Gton, corresponding to 5 to 7% decline comparing to 2019.

As expected, the lockdown has not been enough to stop the loss of sea ice in the poles, according to a study published in Geophysical Research Letters, where scientists examined the sea ice loss in the Arctic based on 40 climate models. They concluded that the Arctic might be completely sea ice free in September before 2050, because as discussed, persistent gases will remain in the atmosphere.

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Author: Ricardo Ramos

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Nature recently published a study illustrating these changes in the marine fish communities of the Barents Sea. From 2004-2012, the temperature in the Barents Sea increased, the mixed boreal-Arctic area expanded and the sea ice decreased, leading to a shift in the distribution of fish species northwards and eastwards (shown in the figure below). The Arctic community [1], normally found in colder areas with most ice, retreated and was confined to the northernmost areas of the study, moving 159 km north. At the same time, the Atlantic shallow sub-community, previously located in the warmest regions, moved 141 km. In terms of abundance, most Atlantic species increased their numbers whereas the opposite was verified for Arctic species.

The pace of these range shifts is quite fast, especially compared to the global average predicted as 40 km per decade. The consequences include possible increases in predation and competition for Arctic species, that coupled with loss of habitat and food availability may have led to the observed declines in abundance. Long term, these changes in fish communities may have effects on ecosystem functioning and vulnerability.

[1] Arctic communities are dominated by bigeye sculpin (Triglops nybelini), Greenland halibut (Reinhardtius hippoglossoides) and snailfish (Liparis spp.) while Atlantic shallow commiunities are dominated by rough dab (Hippoglossoides platessoides), cod (Gadus morhua) and haddock (Melanogrammus aeglefinus).

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Sources: Fossheim M, Primicerio R, Johannesen E, et al (2015) Recent warming leads to a rapid borealization of fish communities in the Arctic. Nature 5:673–678. doi: 10.1038/NCLIMATE2647

Author: Sara Pedro