Glaciers, especially tidal glaciers, maybe much more sensitive to global warming than expected. The fault lies with previously underestimated ocean/glacier interactions. This is the conclusion that researchers draw measurements from robots onboard kayaks.
There are different types of glaciers. First, the huge continental glaciers like those of Greenland or Antarctica. And then there are glaciers called valley glaciers. These are the ones we usually imagine. But there are also tidal glaciers that extend to meet the oceans. And researchers at Rutgers University in the United States are warning us today that they seem to be melting much faster than expected.
In this conclusion, the researchers draw from work on the LeConte Glacier, Alaska. Using robots onboard kayaks, they analyzed the waters released by melting ice where the glacier meets the ocean, and up to about thirty kilometers. “We have observed layers of concentrated meltwater seeping into the ocean and revealing the critical importance of this previously neglected process in modeling,” oceanographer Rebecca Jackson said in a university news release. Rutgers.
Towards a revision of sea-level rise estimates
This work follows a study published in July 2019. It had reported melting rates of these tidal glaciers some 100 times higher than expected. But without being able to really explain them. This time, the researchers resolutely point to the essential role of what they call ambient fusion. Understand, melting ice from direct contact with ocean waters.
These results challenge established models that define ocean-glacier interactions. They should help to better understand the underwater melting of ice. And thus, allow a better assessment of sea-level rise in the context of global warming. For a while in Alaska, only 50 glaciers out of 100,000 are tidal glaciers, they are also among the largest.
Glaciers in the Alps are at risk of melting to 90% by 2100
Glaciers in the Alps are likely to melt to more than 90% by the end of the century if nothing is done to reduce greenhouse gas emissions that cause global warming, according to another study published in The Cryosphere. The 4,000 or so alpine glaciers, tourist attractions that also provide water in the summer to millions of people, are threatened by emissions related to human activity.
A team of Swiss researchers used climate models coupled with glacier measurements to estimate their evolution under various warming scenarios. If emissions reach a ceiling within a few years before rapidly decreasing to 2100, only one-third of the volume of these glaciers would survive. But if emissions continue at their current rate, the prediction is even bleaker.
Impact of global warming
This analysis allowed the researchers to show that more than half of the annual variations in the mass balances (of melting) of these glaciers were identical throughout the alpine chain: two glaciers 10 km apart had 80% common variations (variance) and two glaciers 400 km apart had more than 52% common variations. This is much more than anything that had been shown before. This study published in Geophysical Research Letter reveals that climate fluctuations are very similar throughout the Alps, from Austria to France, over 400 km.
In addition, the researchers have shown a very strong acceleration in the melting of these glaciers over the past decade, much greater than that estimated by previous studies. This acceleration is equivalent to an additional 1.8 m of ice-high per year compared to the 1962-1982 reference period when alpine glaciers were in a near-equilibrium situation, i.e. without significant change.
The scientist notes, however, that the intensity of the melting of alpine glaciers is subject to a large geographical variation. This could be explained by a difference in climate and altitude: in the south, the mountains are lower than in the north and there is more precipitation to the north, which favors the renewal of snow cover. This then increases the albedo, which reduces the temperature and facilitates the reformation of ice.
This phenomenon also poses an unexpected problem, highlighted in 2009 by a Swiss study: when glaciers melt, they release pollutants that had previously been trapped. The presence of pesticides, including the organochlorine family, had been demonstrated in the waters of a lake below a glacier. Melting glaciers in the Alps or other regions, such as the Arctic, can be a nasty surprise. One of the many indirect effects of global warming!