India is far away from Antarctica and the proceedings that take place over there should not be of concern to it. This is the feeling of most of us sane Indians. However, the natural system that the Earth is operating and dealing with leaves no room for such complacency. The Earth is an integrated system and no two places on it are immune to seemingly isolated processes operating in those realms. Hence, what happens in Antarctica should necessarily be our concern.
The South Pole was reached by a party of Norwegian explorers under the command of Roald Amundsen on 14 December 1911, and a wealth of information has been collected since then. In fact, India is carrying out many scientific investigations in and around the icy and dicey environments of Antarctica, since 1981. Even though India is an equatorial country, it has its presence in both the Polar Regions.
Antarctic geomagnetism has special importance for India since Maitri, DakshinGangotri and Bharti (all three locat¬ed at about 70o S, 12o E geographic), are the only places where India can carry out research on high-latitude geomagnetism and other sciences. Direct deposition of solar wind energy occurs at latitudes exceeding 60o geomagnetic latitude. The lower latitudes, where India is located, are shielded from direct energy transfer by the closed magnetic field line structure prevalent in this part of the world. Most of the developed countries directly witness this solar-terrestrial energy transmission by virtue of their geographic loca¬tion. The Indian Polar venture has given a rare oppor¬tunity to study this phenomenon in situ.
One of the magnificent phenomena occurring around Polar Regions is the aurora. These are the curtains of colored luminosity that are a treat to watch. The play of light and hue has inspired many to distill its essence in poetry and art. They are magnificent displays of light that cloak Polar Regions with brightness and incredible splendor. However, the scientists are swayed, apart from its beauty, by the urge to understand the processes that bring about the surreal psychedelic effect that they create. The aurora is connected to the magnetic field of the Earth and the flares on Sun. The interaction of the charged particles from Sun and the atmospheric elements like oxygen, nitrogen, hydrogen are responsible for the mix and match of light colors. The composition of the Polar atmosphere and the structure of magnetic field lines can be understood by studying the aurora.
The fundamental similarity between magnetism and electricity can also be observed in the atmosphere where the charged particles from Sun create currents that have a global and regional sweep. The solar quiet currents are global in nature, while the Polar currents are regional and specific to the ‘earthern’ ends. The solar quiet condition refers to the state of Sun when there are no major explosions or activity on its surface. During such phases, the flow of charged particles towards Earth is almost constant and steady. It is like a car cruising at a speed of 40 km per hour on an expressway. But when there is an explosion on Sun, the charged particles gather tremendous speed and hurtle towards Earth with an incredible hustle. It is like a car speeding at 1000 km per hour on an expressway.
The solar quiet current does not extend till the Polar Regions. But, it is not too far away from magnetic Poles either. There are in fact two poles- geographic and magnetic. The aurora and other related phenomena are associated with magnetic Polar Regions.
The Indian Antarctic station Maitri occupies a unique subauroral (near-aurora) location during geomagnetic quiet condition and records the signatures of southern limb of solar quiet current system. With increasing magnetic activity, the auroral zone expands equatorwards and encompasses Maitri. During such periods, Maitri is temporarily influenced by auroral currents. This movement of shifting in and out of auroral zone makes Maitri an ideal location for space weather studies.
The enhanced geomagnetic activity, which is often called geomagnetic disturbance, releases excessive charged particles. This is the manifestation of dynamic processes active on Sun. The passage of these charged particles through various atmospheric layers of Earth is monitored with the help of an instrument called imaging riometer. This riometer is placed at Maitri and is an integral part of space weather research.
Schumann resonances are global electromagnetic resonances, generated and excited by lightning discharges in the cavity formed by the Earth's surface and the ionosphere. Lightning channels behave like huge antennas that radiate electromagnetic energy at frequencies below about 100 kHz. These signals are very weak at large distances from the lightning source. But the Earth–ionosphere waveguide behaves like a resonator at extremely low frequencies and amplifies the spectral signals from lightning. Determining the spatial lightning distribution from Schumann resonance records is a complex problem at mid- and high-latitude regions. But, this is not the case at Polar Regions. Studies on Schumann resonances help monitor global temperature by quantifying contribution of different atmospheric components to climate change.
Just like earthquakes, blizzards can be very destructive on the icy continent. It has claimed lives of many adventurous explorers and naturalists. These were found to be associated with currents and electromagnetic field at Antarctica. Studies on current pattern revealed electric field decreases to zero or becomes negative, just 2-3 hr before the onset of an blizzard. The existence of atmospheric current was also found to be associated with global thunderstorm activity. Monitoring the current activity prevailing within the Antarctic domain can save precious lives.
The magnetic field of the Earth is not uniform everywhere. It keeps on changing from time to time and place to place. Because of this fickleness the geomagnetic field has to be monitored continuously. The populated areas do not have any problem to undertake this task of ‘keeping watch’. It, however, becomes difficult to carry out such magnetic surveys in remote areas. They are much more difficult in places such as Antarctica where there are fewer people-friendly patches to launch such programs from. Permanent Antarctic stations offer us this luxury. The magnetic observations carried with the help of Proton Precession Magnetometer at DakshinGangotri and Maitri revealed the field was rapidly declining, at the rate of more than 110 nT per year. The global average decrease is 40 nT per year. These observations are important, to feed in data, to carry out computer modeling and simulation processes, that may be operative at Earth’s core-mantle boundary.
Magnetic anomaly map was also prepared for the new Antarctic station Bharati, situated on Larsmann Hills, East Antarctica. The studies show it to be a prominent high magnetic ridge with values of ~5000 nT higher than the surrounding area values.
Secular variation refers to the variation of the main field of the Earth on timescales of the order of tens of years and longer. Studies to understand characteristics of secular variation, in total magnetic field, at Antarctica were carried to determine average dipole, quadrapole and octapole fields and their contribution to the total field variation. The Antarctic region also shows an absence of westward drift, which is a prominent feature of secular variation at some locations. A region of peak decrease in total field in the Antarctic region is seen to be stationary. The rate of decrease of this feature is to the tune of ~100 nT/year and the magnitude of this decrease is itself falling since 1980. The dipole field variation contributes less than 40% to this feature and the quadrupole and octapole fields are inferred to contribute to increasing field.
This implies large contribution comes from within the Antarctic region. Recent studies of secular variation at the core-mantle boundary have postulated that flux expulsion, resulting from fluid upwellings, may be the likely cause of secular variation in the high latitude regions of southern hemisphere. The northern hemisphere also has a long-lived region of decreasing total magnetic field, but this is located at the mid latitudes.
The breaking of Larsen C ice shelf has attracted worldwide attention, which is a good sign, signaling the concern of the world policy-makers and the laity. The secession of a large chunk of ice from its parent body is not just a spectacle that should be marveled and forgotten. It will have wide implications on the global climate whose effects will not be instantaneously evident. It will take time to percolate and influence the natural processes. The thick ice shelves are prone to ceding from each other or breaking into splinters. This process has been going on for years and will go on as well. However, how much of the splintering is due to natural causes and how much because of anthropogenic activity remains to be seen.
The icebergs and their movement is being tracked by different methodologies and techniques by scientists from all over the world. India is also monitoring some of the ice chunks for their movement. The actual movement or the shrinkage is important to understand how much water is added to the sea. The relative sea level changes are related to the water addition from the glaciers. The ice sheets and ice shelves, as well as the icebergs, make it difficult for the melted glacier water to enter the ocean. The tiny fluid trickle from the glaciers gets deposited on the ice sheets, which progressively gain in size and thickness.
The accumulated ice sheets, in fact, are a treasure trove of climatic and environmental signatures that are hidden within their confines. The ice sheets, many a times, contain within them blobs of atmospheric gases and elements. It is like the Earth has written a small blog on the kind of environment present, at or before the time, of confinement of these elements. When this frozen water melts, due to various reasons, it has the potential to raise the sea level in many coastal parts of the world. In the past, the eastern coastal belt of India was inundated quite a few times when the ice sheets at Antarctica started to melt away.
In the not so close neighborhood of the current break-up at Larsen C, scientists from the Indian Institute of Geomagnetism have been monitoring Schirmarcher glacier in Antarctica with the help of GPS. The studies revealed the glacier was moving horizontally in north-northeast direction, with an average velocity of approximately 6 m per year.
Monitoring the rate of growth or shrinkage of the glaciers is more important than the laceration of icebergs. The icebergs have a limited role to play in the climate cycle compared to the Polar glaciers. The broken chunk of Larsen C iceberg will be floating and rafting through the waters for an appreciable period of time. It will be a minor nuisance to the ships voyaging through the Antarctican waters, before it melts completely when it comes in contact with the warm waters. It will then have some effect on the nearby coastal areas by way of rise in sea level.
Till then we need not worry on this count.