A Journey in Antarctica by Sergio Rossi

Author:Sergio Rossi
Language: eng
Format: epub
ISBN: 9783030894924
Publisher: Springer International Publishing

Poles Apart

Why are there asymmetries between the North and South Pole? What is the reason for the Arctic seeing such drastic changes in a short time and in the Antarctic taking longer? In the past, warming at the poles has not been simultaneous either, and paleoclimatic models have shown that the changes (accelerated in the north) end up having repercussions in the south. The connections are atmospheric and oceanic. Everything is connected by these invisible ribbons that transfer heat or cold from one point of the planet to another, accelerated to varying extents by marine currents. They may take hundreds or thousands of years to occur, but at a certain point there is no return. The deep ocean connection is undoubtedly the most important function for understanding the impact of one pole on another, demonstrated in part by the existence of some 230 species at more than 14,000 km distant.

The cause of the asymmetry is varied. The Arctic has more sea; in fact, apart from the huge island of Greenland, it is all sea, capable of absorbing much more heat than a frozen continent like Antarctica. That is one of the keys to understanding the differences, but not the only one. In Antarctica the hole in the ozone layer can extend to 90% at certain times and areas, while in the Arctic it never reaches such values. Ozone has to do with the capacity to retain the cold and not to heat up the atmosphere. As we have seen, the decrease in ice cover will change energy flows. “While the Arctic has lost, on average, about 57,000 km3 of sea ice per year from 1979 to 2017, Antarctica appears to have gained about 11,000 km3 of that same seasonal ice per year,” says Ted Maksym of the Woods Hole Oceanographic Institution (United States). And thickness—that is, multi-year ice—has also been lost. In the Arctic, 40% of this thickness was lost between 1980 and 2000, with the loss accelerating to as much as 0.6 m per year in certain areas.

Ice, especially when covered with snow, has a higher albedo (as mentioned above, the ability to “bounce” sunlight back): ice with snow has an albedo of up to 0.9, while water alone has an albedo of no more than 0.05. Less ice cover means more warming of the water, and thus of the whole system. This creates positive feedback: less ice means more heat absorption, which melts more ice, which causes more heat absorption. But as we have seen in the ice, algae can congregate and create an ecosystem of their own.

Let’s focus on the Arctic and its changes. In a single liter of ice there can be up to 1 mg of chlorophyll concentrated in a few centimeters of depth, which is very high compared to the 0.005 to 0.010 mg per liter in the rich polar waters around it. Many organisms that depend on this food source are affected, such as krill. In this case, this tiny crustacean draws not only energy from these algae but sun protection, its resistance to ultraviolet rays.

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.