New Delhi, Jan 20: Researchers have found that Antarctica’s Pine Island Glacier (PIG) is melting beyond the point of ‘no return’. The glacier, which is more than 160,000 sq km, is capable of contributing 3.5-10 mm to the rising sea level in the next 20 years. These changes in Antarctica’s climate parameters influence the Indian monsoon in all likelihood; efforts are being made to find the connection between the two.
Rasik Ravindra, currently the Professor at Earth System Sciences Organisation (ESSO). Ministry of Earth Sciences (MoES), and former Director of National Centre for Antarctic and Ocean Research, talks with Sulagna Chattopadhyay, the editor of G’nY, about the latest study on the PIG and the use of Antarctic science to predict monsoon.
A new study (12th Jan 2014) by scientists at the French National Center for Scientific Research in Grenoble claim that 20 per cent ice flow of the Antarctic will collapse in a few decades. What are your views based on your work?
The study speaks of the acceleration in the loss of the glacier mass in Western Antarctica and not of whole of Antarctica. The ice sheet in eastern Antarctica which constitutes a major part of Antarctica’s ice cover is so far in equilibrium. There is, therefore, no question of collapse of 20 per cent of ice flow of Antarctica in a few decades. The paper in question is a study by L.Favier, G Durand and others on Pine Island Glacier situated in Western Antarctica, which is calving at an alarming rate as shown by the data collected by glaciologist over 40 years. The Pine Island Glacier is one of the coastal glaciers, and accounts for about 20 per cent of ice flow on western Antarctica. It is a well known fact that Antarctic Peninsula and the western Antarctica are warming at a rate higher than the rest of Antarctica.
The sea surface temperatures in Western Antarctica are warmer and this warmer water is believed to seep underneath the glacier lubricating the base of the glacier, causing it to melt faster. There is also an underwater trench close to the grounding line of Pine Island glacier, which has made things worse.
In most of the coastal regions of Eastern Antarctica, excepting the Lambert glacier of Prydz bay, a wide zone of ice shelf lies between the glaciers (ice sheet) and the sea, thereby protecting the direct loss of ice flow.
The very latest satellite data details the thinning occurring in this region of West Antarctica (Photo courtesy: bbc.co.uk)
The French National Center for Scientific Research claims to have now developed state-of-the-art models for glacier prediction. Does India have access to or has it developed any such models? If yes, what have been its findings?
The models that have been developed or used for projecting the loss of ice flow are specific to conditions prevalent in a specific environment. While it has been stated that the Pine Island Glacier has recorded ice mass loss at an average 20 Giga tonnes/year between 1992-2011, some workers such as Pierre Dutrieux et al (2014) have pointed out a strong sensitivity of ice shelf to climate variability in this area. They have recorded large fluctuation in the oceanic heat in Pine Island bay, stating that the oceanic melting of the ice sheet into which the glacier flows, decreased by 50 per cent between 2010 and 2012 possibly due to La-Nino weather event.
The studies on Indian glaciers have been focusing on the mass balance i.e. loss or gain of the ice mass, recession or advancement of the snout of glacier through ground based and remote sensing techniques. For developing a model that would lead to predicting mass balance, long term data is required on several parameters such as precipitation, temperatures, wind pattern, humidity, albedo, bed rock topography, thickness of the glacier, volume of melt water discharge, black carbon/aerosol concentration etc. Though continuous monitoring of the glaciers in India is comparatively a recent phenomenon, attempts are being made by several workers to develop models that would suit different glaciers (debris free or debris covered) located in different climatic zones.
Has Antarctic science been a help to monsoon predictions?
Climate change has been one of the major thrust areas of Antarctic science world over and India is no exception. To include the Antarctic climatic parameters into the models used for predicting Indian monsoon rainfall, one has to establish first the teleconnections between the two. There are several attempts being made by Indian and international workers to establish links/association between Antarctic Sea Ice extension and Southern Ocean oscillations with the monsoon rainfall. Some of the significant studies on this aspect are summarized below.
Examination of the data for 1901-1981 period for the summer monsoon rainfall and the Darwin pressure anomalies by Shukla and Paolino (1983) have shown that “the tendency of the Darwin pressure anomaly before the monsoon season is a good indicator of the monsoon rainfall anomaly. An above normal Darwin pressure during March, April and May, and increasing seasonal pressure anomaly is a good indicator of the non-occurrence of very heavy rain over India”.
Huigao, Yunyun Liv etc in their work published in Chinese Science Bulletin in 2013 have concluded that stronger Antarctic Oscillation has substantial effect on the tropical-inter tropical convergence zone. As a result of increase in the Pressure gradient between subtropical and tropical region in spring, the Somalian Cross Equatorial Flow occurs earlier and enhances the westerlies over tropical Indian Ocean.
There are several studies on the teleconnections of Antarctic Sea Ice extent with the Indian Summer Monsoons.
Xiaojun Yuan and D G Martinson (2001) have established the nature of inter annual variability of Antarctic Sea Ice and its relationship with tropical Climate. They conclude that the Antarctic Dipole is associated with tropical ENSO (El Nino-Southern Oscillation) events.
Ivchenko et al (2004) also have suggested a possible direct mechanism by which extra-tropical Ocean can induce anomalies in the equatorial Ocean.
For example, Dugam and Kakadi (2004) found out that the deficient Monsoon years were preceded by more than normal Sea-Ice Extent and vice-versa.
Amita Prabhu and co-workers (2009) have worked on the connection between Antarctic Sea ice Extent and Summer Monsoon rainfall of India. Cross-correlation of the anomalous Summer Rainfall data and Antarctic Sea-Ice extent for the period 1988-2005 by them has revealed that “coherent propagating pattern is clearly evident between the two. Sea Ice Extent of Western pacific Ocean Sector in month of March has a strong association with that of Summer Monsoon rainfall of India in the same year”.
Another study by Amita Prabhu et al (2010) focuses on the Role of Antarctic Circumpolar Wave in modulating the extreme of Indian Summer Monsoon rainfall. The analyses of data for the period 1980-2005 by them has shown that Sea Ice Extent over Bellingshausen and Amundsen Sea Sector of Antarctica, during Austral Summer has an inverse relationship with Indian Summer Monsoon rainfall of the following year. They have shown that “oceanic and atmospheric mode of Antarctic Circumpolar Wave play a significant role in modulating the All India Summer Monsoon rainfall.” White et al (2002) has also shown that Atmospheric and Oceanic teleconnections link Antarctic Circumpolar wave in the Southern Ocean and the global ENSO in the tropical Indo-Pacific Ocean.