Unnoticed by science and people: 240 Hiroshima-bombs outburst floods
Staff Writer |
Researchers from Niels Bohr Institute, University of Copenhagen, Denmark, studied satellite photographs of Lake Catalina, an ice-dammed lake in East Greenland - and were truly amazed.
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Unnoticed by science as well as people living in the area, the lake has been the source of four major outburst floods over the last 50 years - each representing an astounding mass of energy, equaling up to 240 Hiroshima-bombs!
"The next outburst is certainly building and may happen as soon as 2018-19," says Aslak Grinsted, head of the research team.
If a glacier keeping back an ice-dammed lake starts leaking, the end result may be emission of almost unfathomable quantities of water in the form of an outburst flood.
For the last 200 years science has recorded a considerable number of outburst floods from ice-dammed lakes in mountainous regions all over the globe from Norway to USA, Iceland, Kyrgyzstan, Canada, Austria and Switzerland.
In most cases it has been known in advance that an outburst was under way, prompting some state of alert in order to avoid loss of lives.
However, some of the biggest outburst floods ever recorded have remained unknown until recently.
These outbursts - a total of four taking place between 1966 and 2012 - originate from Lake Catalina, an ice-dammed lake on Renland, a 100 kilometer long island in Scoresbysund Fjord in East Greenland, located about 180 kilometer west of Scoresbysund settlement (Ittoqqortoormiit).
And each of these outbursts has released in the order of 2.6-3.4 cubic kilometer of fresh water!
3.4 cubic kilometer of water is somewhat more than a shower - it equals 3.400 billion liter. Which, according to scientific reports covering the period from 1818 till present, has catapulted Lake Catalina into the top-5 rankings on the all-time-great-chart of registered outburst floods coming from ice-dammed lakes; surpassed only by outbursts in Argentina and USA with a thumping one - 5.400 billion liter from Hubbard Glacier in Alaska in 1986 - as the undisputed record holder.
All details regarding the Greenlandic mega outbursts will 'go public' via an article appearing in the upcoming issue of Scientific Reports.
"These colossal outbursts from Lake Catalina were detected by mere chance," admits assistant professor Aslak Grinsted, who led the study. "We learned that a number of different satellites have taken photos of Lake Catalina over the last 50 years, from 1966-2016. These pictures are now freely accessible, and when we decided to take a look at them and soon after started to compare them systematically, they provided information about remarkable fluctuations in the water level of the lake."
"This was how we detected the four outburst floods from Lake Catalina that have all taken place during the winter season, typically from November to March," says Aslak Grinsted: "The first between 1966 and 1972, the second in 1988-89, the third in 2003-2004 - and the last in 2011-12."
By analyzing data from the photographs the scientists were able to construct a model which - with some certainty - can predict when the next outburst flood from the lake can be expected to take place, explains Aslak Grinsted: "It is certainly building right now, and according to the model it will happen at the latest in 2023. However, it may occur as soon as next year, in the winter of 2018-19."
The uncertainty surrounding the advent of the next mega outburst from Catalina Lake can be attributed to the rising temperatures experienced in Greenland and in the arctic regions these years due to global warming - increasing the melt down of glaciers and thereby making barriers keeping water 'inboard' in ice-dammed lakes leaking sooner than expected, explains Aslak Grinsted.
Seen from a distance, Renland's ice cap - towering some 2.500 meter above Scoresbysund Fjord - almost creates the illusion that the rocky and steep-sided island is wearing white winter headgear.
Lake Catalina - named after the legendary American built amphibious aircraft used to carry out aerial mapping of Greenland during the 1950s - is situated 600 meter above sea level in a valley.
Two smaller lakes further up the mountain feed it with water melting off Renland's ice cap during the summer season - and feed it well, as Aslak Grinsted points out. "It's no pond - Lake Catalina is about 10 kilometer long and on average two kilometer wide, and in some parts it may well be hundreds of meter deep.
"To the best of my knowledge, the depths have never been systematically charted - though a number of expeditions have visited the lake over the years, some have even sailed on it, with a French expedition in the summer of 2016 being the latest." ■