The chemistry of the Antarctic polar vortex has created severe ozone depletion . What is Polar Vortex? How does it explain the absence of An Arctic Hole as compared to a more prominent Antarctic Hole? (200 Words)
A polar vertex is a continuous and massive (about 1000km in diameter) cyclone about the Earth‘s geographical poles. The centres of these cyclones are low-pressure zones and are surrounded by the polar high-pressure zones. Their cores strengthen in the winter and weaken in summer, primarily due to the presence of high temperature systems in the Eastern or West Pacific during the summers which displaces the cold air from the poles, thereby weakening them.
The Arctic polar vortex is weaker than the one in the Antarctic as the distribution of land masses in the Arctic region gives rise to Rossby waves which cause a breakdown of the vortex, while in the Antarctic region, the vortex remains less disturbed. Now, this breaking up of the vortex in the Arctic results in exchange of winds between the poles and the high pressure regions of the mid-latitude.
Meanwhile in the South Pole, the low temperatures during winters caused the formation of extremely small icy particles which in turn form polar stratospheric clouds(PSCs). The numerous chlorine-bonded molecules now start binding with the icy particles and in the process chlorine is released. During the summer months the UV rays of the sunlight breakup the chlorine molecules into radicals, resulting in massive ozone destruction.
Although this phenomenon is also observed in the Arctic, its impact is much less pronounced due to the greater air exchange in the North Pole. However, the shifts in the northern vortex have often caused other problems such as immense lowering of the winter temperatures in countries like the USA and Canada.
In recent years, scientists are posed with several problems such as increase in ice while reaching to Antarctic research stations to supply essentials to their respective stations. What could be the possible reasons for such anomalies? Explain. (200 Words)
The sea ice around the Antarctic has seen highest level since few years. This has posed serious problems for scientist to supply essentials to the research stations. Transportation by helicopter is not sustainable as it involves significant financial resources. There is a need to develop accurate models to predict the behaviour and thickness of sea ice, so as to arrange the kind of ice breaker needed to carry supplies.
Reasons:
- Drop in ozone levels over Antarctica. The hole in the ozone layer above the South Pole has caused cooling in the stratosphere. A side-effect is a strengthening of the cyclonic winds that circle the Antarctic continent. The wind pushes sea ice around, creating areas of open water known as polynyas. More polynyas leads to increased sea ice production.
- Changes in ocean circulation. The Southern Ocean consists of a layer of cold water near the surface and a layer of warmer water below. Water from the warmer layer rises up to the surface, melting sea ice. However, as air temperatures warm, the amount of rain and snowfall also increases. This freshens the surface waters, leading to a surface layer less dense than the saltier, warmer water below. The layers become more stratified and mix less. Less heat is transported upwards from the deeper, warmer layer. Hence less sea ice is melted.
- Landmass near Antarctic Ocean are absent as compared to Arctic Ocean where it is surrounded by Denmark, Greenland and Russia. This leads to unrestricted growth of sea ice.
- The El Nino changes the southern oscillations by changing the prevalent pressure conditons, this affects the wind directions near Antarctic which drives changes in sea ice.