Indian researchers have documented accelerated glacial melting at an Arctic fjord, a much-discussed factor projected to influence Indian monsoon with changing global climate.
By Sahana Ghosh
The frigid Arctic, which keeps losing ice due to global warming, is one of the batteries feeding the variations in Indian monsoons, over 7000 kilometres away. Studying the response to the warming in the form of melting is quite relevant to India as it provides us with tools to monitor changes in the Arctic, said scientists at National Centre for Antarctic and Ocean Research (NCAOR), Goa.
This study is of significance in the wake of latest reports which say the Arctic’s “last bastion” of sea ice, off the coast of northern Greenland, is breaking up, highlighting the polar region’s vulnerability to rapidly rising temperatures.
“In a recent study we have shown accelerated glacial melting at Kongsfjorden post 1970s. Arctic glacial melting is a factor considered very important to the Indian monsoon,” Vikash Kumar, scientist at National Centre for Antarctic & Ocean Research and co-author of the study, told Mongabay-India.
Kongsfjorden, is a glacial fjord in Svalbard archipelago in the Arctic Ocean, which harbours a mixture of Arctic flora and fauna. Over the past few decades the fjord has been on the radar of climatologists due to its vulnerability to ongoing warming in the region.
Analysis of the ice allows one to look back in time and recreate past temperatures.
“The glaciers and sea ice cover in the Arctic is responding to the well-established warming that is happening there and it is of concern to us because the Indian monsoon doesn’t occur in isolation. Factors such as El Nino, La Nina and changes in remote Arctic and Antarctic affect monsoons as they contribute to its variability on various timescales,” Vikash Kumar said.
Although the year-to-year changes in summer monsoon rainfall do not statistically exceed more than ten percent, it is this seemingly small but quite significant variability that wreaks havoc in the form of floods and droughts during monsoons, said Kumar.
So to flesh out the possible scenario for the future, the team looked to the environment of the past. They drilled a 21 cm core in Kongsfjorden to examine the sediment for changing glacial melt history in the last 200 years.
“We collected sediment samples that had preserved the signatures of past organic productivity (organic carbon) and these productivities were impacted by changing glacial melt history of the last 200 years. So we reconstructed the warming of the Arctic from 1810 to 2010 by examining the organic productivity from sediment samples,” Kumar explained.
Through this we were able to capture the response to warming in the form of melting, he said, adding, “Our results show that there have been steady periods of warming in the Arctic in the last two centuries. However, there was a short-lived positive swing around 1840 and 1900 when glacial melting was at its lowest. The trend of melting increased after 1900 and accelerated after 1970.”
WATCH : Fast melting Arctic ice may impact the Indian monsoon.
Arctic and the Indian monsoon
As warming continues driving glacial and sea ice cover to melt, freshwater supply to the Arctic ocean is slated to increase.
“Freshwater influx into these fjords and into the overall Arctic basin in general, has immense climatic implications not only limited to the poles but also with serious implications for mid and low latitude regions where most of the civilisation resides,” Kumar noted.
Because of this freshwater that is flushed into the ocean, salinity levels in the sea water take a hit which in turn tinker with ocean currents that transport warm water and precipitation from the equator toward the poles and cold water from the poles back to the tropics.
This disruption in ocean currents may lead to increasing temperature difference between land and sea in the tropical regions and this land-sea asymmetry is associated with the monsoon circulation.
Kumar described the Arctic’s influence on monsoon in India, a largely tropical region, as “complex.”
“While a general warming of the northern high latitudes itself may perhaps initially increase the summer monsoon rainfall due to associated air-sea interaction, its influence once the warming percolates down to the lower latitudes largely remains an outstanding question,” he said.
This can only be answered with help of reliable climate models or by reconstructing past monsoon behaviour during periods with warming levels as high or greater than the present, pointed out Kumar.
Fortunately, such modern day climate analogues in the geologic past exist and NCAOR is currently working on projects such as the “Pliocene Arctic Climate Teleconnections”, an international project funded by the Norwegian Research Council, he said.
What is known till now with respect to the past few decades of warming is that although there is no clear trend in monsoon rainfall due to a warmer climate, the frequency of extreme rainfall events have increased and moderate to low-intensity rainfall events have declined.
One of region’s direct association with the Indian summer rainfall is the Arctic Oscillation (AO), a climate pattern characterised by winds circulating counter clockwise around the Arctic at around 55°N latitude.
“During the positive phase of the Arctic Oscillation, jet streams are on a more northerly track, which results in higher than average atmospheric temperature over the Indian landmass, a condition favourable for monsoon circulation,” Kumar said.
Through their earlier work, the researchers paved the way to peep into past changes in salinity due to glacial melting. Historic changes in salinity at the site can indirectly provide valuable insights into past episodes of warming and freshwater supply in the region.
The previous study provided new information and tools that will make it easier to monitor current melting and freshwater movement at Kongsfjorden.
According to 2013 IPCC projections as glacier melt in Greenland and in parts of Antarctica is accelerating, sea-level rise — in the range of 26 to 82 centimetres by 2100 according to the latest IPCC projections — will increase the risk of flooding at many coastlines.
In 2017, the Arctic Monitoring and Assessment Programme stressed that the Arctic is warming more than twice as fast as the rest of the planet.
Vikash Kumar explained how the Arctic is “intrinsically coupled” to the global climate system.
Two of the very important phenomena in the Arctic, from a climate perspective, are reflection of solar radiation back to the space from the shining surface of ice (albedo effect) and deep-water formation and thermohaline circulation (great conveyer belt of ocean circulation that redistributes heat between tropics and the poles and maintains climatic balance).
“Both these processes are under pressure due to warming and melting in the Arctic region. In the absence of these two vital processes, we would have a much warmer planet overall and with a much greater temperature difference between the poles and the tropics. Additionally, thawing of permafrost Arctic will cause enhanced loading of greenhouse gases into the atmosphere,” he said.
“What is worrying however is the fact that all these processes operate in a positive feedback loop, which may cause a runaway warming of the planet,” Kumar added.
Kumar, V., Tiwari, M., & Rengarajan, R. (2018). Warming in the Arctic Captured by productivity variability at an Arctic Fjord over the past two centuries. PloS one, 13(8), e0201456.
Tiwari, M., Nagoji, S., Kumar, V., Tripathi, S., & Behera, P. (2018). Oxygen isotope-salinity relation in an Arctic fjord (Kongsfjorden): Implications to hydrographic variability. Geoscience Frontiers
(This article was originally published on Mongabay India – an environmental science and conservation news and information site. You can read the original article here.)