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Antarctic sea ice melt favors cloud formation

May 13, 2021

A new study published in Nature Geoscience led by the Institut de Ciències del Mar (ICM) and the University of Birmingham (UK) has revealed that Antarctic sea ice melt enhances the formation of aerosols in the atmosphere which, in turn, favors cloud formation in summer and could help reduce the solar radiation received by the region and have important climate consequences. From data collected during the PI-ICE 2019 Antarctic campaign, led by Manuel Dall'Osto, researchers found that when air masses come from areas around the sea ice margin, aerosol formation episodes are more frequent. According to the study, these air masses contain high concentrations of sulphuric acid and amines, which are compounds of biological origin that interact with each other to transform from gases to particles. Although the role of sulphuric acid in the formation of polar aerosols was already known, this is the first study that demonstrates the key role of amines, nitrogen-containing organic compounds produced by the degradation of organic matter by micro-organisms that inhabit the sea ice. This confirms that emissions from marine plankton and sea ice melt play a crucial role in regulating Antarctic climate.

Brean, J., Dall’Osto, M., Simó, R., Shi, Z., Beddows, D. C. S., and Harrison, R. M. (2021). Open ocean and coastal new particle formation from sulfuric acid and amines around the Antarctic Peninsula. Nature Geoscience, 14, 383–388.

 

Changes in the CO2 regulating capacity of the Southern Ocean

October 21, 2019

The capacity of the Southern Ocean for regulating atmospheric CO2 has varied in the past. This is what a paleoceanographic study published in Nature Geoscience has recently found. Today, the world’s oceans absorb about one-third of the CO2 that we humans are putting into the atmosphere from the combustion of fossil fuels. From them, the Southern Ocean is the one that contributes most to this sequestration. Almost half of all the oceanic CO2 uptake takes place in the Southern Ocean. This absorption is, of course, very positive; otherwise we would have significantly higher CO2 concentrations in the atmosphere, with the consequent enhanced global warming. However, The Southern Ocean has not always operated in this way. This is what researchers have discovered in this study, which provides a reconstruction of the CO2 regulating capacity of the Southern Ocean over the last 25.000 years. For this, they analyzed specific isotopic ratios of planktonic microfossils and several key organic compounds from a deep-sea sediment core recovered south of Tasmania. With these analyses they reconstructed the evolution of parameters such as seawater temperature (from long chain alkenones) and the acidity (from boron isotopes) in the past. With them, they calculated the variability of the dissolved CO2 in seawater which, by comparison with the record of atmospheric CO2 from Antarctica ice cores, allowed them to determine the CO2 sink or source role of the Southern Ocean during the last glacial to interglacial transition. The results show that the Southern Ocean surface waters in the studied location were a net sink for atmospheric CO2 during glacial times and up until about 12.000 years ago, when they became a net source of CO2 for about 8.000 years. In this varying regulatory role of the Southern Ocean, key factors were the changes in primary productivity and the intensity of marine currents. This study helps to understand the variability of this regulatory role of the Southern Ocean but also alerts about the future capacity of this ocean to continue to absorb CO2, which should not necessarily continue to be as favorable as today. In the event that its capacity to act as a CO2 sink decreased in the future, the global projections on the emissions of this greenhouse gas would be altered to even more alarming levels than the current ones.

Moy, A. D., Palmer, M. R., Howard, W. R., Bijma, J., Cooper, M. J., Calvo, E., et al. (2019). Varied contribution of the Southern Ocean to deglacial atmospheric CO2 rise. Nature Geoscience, 12, 1006–1011.