The effect of global warming on the oceans and on the cryosphere (sea ice, ground ice, permafrost, and snowy areas) are increasingly clear and we are getting closer and closer to the point of no return. This is the message sent by the scientific community which joined the International Cryosphere initiative at COP22 in Marrakech: action to avoid, or at least to slow, the current warming trend is urgently needed by 2030.
Due to global warming, the Glacial Arctic Sea and Greenland are suffering a relentlessly melting process. Polar areas are evaluated to be melting at a rate twice, triple, or even more higher than the terrestrial average, mainly because of the additional effect of oceanic streams flowing along arctic coastal areas.
Overall, Antarctic ice shrinker, but the effect is more evident on the Western Antarctic coasts. The most evident effect of glacial fusion is an average sea-level rise of about 18 cm in the last century, with picks in the Pacific area. Serious consequences for local communities involved, for instance, land evacuation.
Sea levels rise not only because of ice melting, but also due to the thermal expansion caused by an increasingly heating process within the oceans, which accelerated in the last decades (especially in the upper layers).
In addition to that, another oceanic trend is worrying scientists: oceans are currently absorbing about 27% of the CO2 in the atmosphere, and this process accelerates water acidification. The consequences of this are a dangerous melting of calcareous shells for mollusks and plancton, and an increasingly corals whitening process.
Cold waters in the Arctic Ocean and in the Southern Oceans surrounding the Antarctica host a huge variety of sea ecosystems, but they are also extremely sensitive to acidification, which increases due to an increasing amount of absorbed CO2. Significative thresholds in terms of water acidification have already been exceeded in some areas and this process is already affecting some species. The overall risk of acidification relates to its effect on ecosystems through food chain weaknesses and shortage of specific species, which persists even under the positive scenario of a full implementation of the Paris Agreement.
The scientific community stressed the role of permafrost, currently covering 24% of lands belonging to Alaska, Siberia, and Northern Canada. Permafrost damages have consequences not only in terms of ground instability that hamper the correct functioning of transports and infrastructures, but it is also worrying because it slowly releases CO2 and methane that it stored along the centuries.
Estimating the amount of GHGs stored by permafrost is hard, but its role is consistent and it is not yet considered in the total accounting of the emissions budget to which the limit of +2°C refers to. To make it clearer, the amount of GHGs we would be allowed to release if this amount is taken into account, is even smaller than what the Paris Agreement sets down.
It is urgent to act, then. And objectives should, in principle, be much more ambitious than the voluntary contributions agreed last year.
Scientists gave some suggestions with regard to policies and international agreements on oceans’ protection. Now everything is up to government representatives meeting up in COP22: whether they understand the urgency of this issue or not, it is not easy to say.