Polar Vortex—The Winds of Change
The unusually cold winter experienced in various parts of North India, including the national capital, resulted in the lowest temperatures recorded in the last decade. Normal life came to a standstill in cities across the US and Northern Europe with temperatures touching -20 degrees Fahrenheit in several parts around the world. These harsh weather conditions, that have resulted in the death of over twenty people, have been linked to cold blasts from the Arctic, a phenomenon nicknamed the ‘Beast from the East’ or more commonly known as the polar vortex.
Although the term polar vortex has been around since the 1850s, few people had heard of it until earlier this decade, when the winds migrated to more populated parts of North America and Eurasia. The phenomenon had earlier skipped over these regions, and their sudden occurrence in these areas led to some of the coldest winters we’ve seen in recent history. The most famous occurrence of the vortex before now was in 2014, when it lashed across America, completely freezing the Niagara Falls in the process.
Understanding this phenomenon requires an analysis of the Earth’s geological and geographical properties. The thinness of the Earth’s atmosphere results in large temperature variations between the Poles and the Equator. This gradient is smallest in the summer, when the polar regions experience nearly 24 hours of sunlight, and largest in the winter, when it’s almost always night. As a result of this, there exists a persistent, large-scale, rotating, low-pressure zone at each pole. These two zones are known as polar vortices, and they each start a few miles up in the atmosphere and extend well into the stratosphere.
Beneath them, lies a large mass of cold, dense air that surrounds each of the poles. Usually, these vortices are stable and hence stay still throughout the year, sparing North America and Eurasia of such harsh weather. When the polar vortex around the North Pole weakens, it causes much of the cold air to mix with the warm air in the mid-latitudes. This pushes the jet stream south, bringing cold air to highly populated areas, and creates the conditions for the occurrence of a cold snap.
Sudden stratospheric warming (SSW), that occurs when the upper layers of the atmosphere rise in temperature by approximately 30–50 °C (54–90 °F) in the span of a few days, has been credited as having a huge impact on the weakening of the vortices. Warmer land temperatures, particularly in northern North America and northern Eurasia, allowed more heat to be transported into the Arctic stratosphere. Global climate change and weather phenomenon such as the El Nino affect the warming of the stratosphere, and hence contribute to the destabilisation of the polar vortex and the subsequent formation of cold snaps.
The polar vortex had a widespread effect on the US and Europe. A total of 22 states in the US were affected, with states like Chicago facing temperatures as low as -37°C and North Dakota hitting -54°C. Twenty-one people died due to the polar vortex in the US alone. The US Postal Service called a halt to mail deliveries in parts of 10 states in the Great Plains and hundreds of schools, colleges and universities, were closed in the affected regions. The entire town of Hell, Michigan along with Lake Michigan froze over, which made these parts of the US colder than Antarctica.
The effect of polar vortex was not limited to Europe and the US. The long winter in parts of North India has been attributed to the polar vortex and the western disturbances. Many parts of the Himalayas saw episodes of heavy snowfall and the effect was felt across North India and even in the southern states of Maharashtra and Telangana, which witnessed colder temperatures. Temperatures dipped below zero in some parts of Rajasthan, which has happened only thrice before in the last decade.
“Western disturbances are low-pressure winds that travel westwards from the Mediterranean region bringing cold winds which impact the northern parts of India particularly the Himalayas. The cold from the Arctic has been spilling southwards into Europe and the US due to the weakening of westerly currents. This seems to push western disturbances more southwards than normal towards northern India. In effect, this is transmitting the cold from southern Europe into north India,” said D Sivananda Pai, head of IMD’s long-range forecasting, while talking to the Times of India. This January, seven WDs hit north India as opposed to the normal of four to six. This resulted in heavy to moderate snowfall across the northern parts of India during January.
As the Earth continues to warm, extreme weather events like this will become more common, with many climatologists predicting an unstable polar vortex bringing storms like this to the world multiple times per decade and conditions will get worse each time they come around. As the extent of sea ice reaches record lows, the temperatures in the Arctic have reached record highs. Global weather patterns are undergoing massive changes, courtesy of global warming and human exploitation of the environment, as ‘normal’ weather conditions give way to these anomalies.
Featured Image Credits: ABC News