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Is a lake on Greenland cracking up? Well, according to recent research, meltwater lake on a glacier located at 79 degrees north latitude triggers lasting cracks and ice uplift. Hello friends, Jim here. So, what is going on?
This is a top view taken from a helicopter of this deep lake located at 79° north latitude. Since the mid 1990s, the Greenland ice sheet has been losing mass, leaving only three floating tongues remaining. One of these, and I'll try my best to pronounce it, is Norg Halert Bry or the 79 degree north glacier, probably easier to refer to it that way, is already showing the first signs of instability.
In a new study, researchers from the Alfred Vegner Institute investigated how, caused by global warming, a 21 square kilometer large meltwater lake formed and developed on the surface of this glacier. They observed that over the years this lake has caused gigantic cracks and the outflowing water is lifting the glacier. Their findings have been published in the journal The Cryossphere.
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The lake first appeared in the observation data of the year 1995. There were no lakes in this area of the 79° degree north glacier before the rise in atmospheric temperatures in the mid 1990s. as professor Angelica Humbert, a glaciologist at the Alfred Vagna Institute, Helmhole Center for Polar Marine Research stated, "From the time of its formation in 1995 until 2023, the lakes's water repeatedly and abruptly drained through channels and cracks in the ice, causing massive amounts of fresh water to reach the edge of the glacier tongue towards the ocean.
There were a total of seven such drainage events, four of which took place in the last five years. During these drainages, extensive triangular fracture fields with cracks in the ice form from 2019 onwards, which are shaped differently from all lake drainages I have seen so far. Humbert says.
Some of these cracks form channels with openings several dozen meters wide, referred to as a mulen. Water flows through these mulens also alter the main drainage of the lake. Meaning that within hours a huge amount of water reaches the base of the ice sheet. This is important; to get all this liquid water reaches the base of the ice sheet. That's where it sits on the bedrock. That's where it lubricates and it makes movement of the glacier easier.
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It can slide easier, but in some cases, as apparently in this situation here, it can cause enough hydrostatic pressure that will then actually lift the ice upwards. For the first time, we have now measured the channels that form in the ice during drainage and how they change over the years, says Humbert. After the lake formed in 1995, its size decreased over time with the first cracks appearing.
In recent years, the drainage has occurred at increasingly shorter intervals. Form the lake quickly drains. basically is what she's saying. We suspect that this is due to the triangular mullens that have been reactivated repeatedly over the years since 2019.
The material behavior of the glacier plays a role here. On the one hand, the ice behaves like an extremely thick viscous fluid that flows slowly over the substrate. At the same time, however, it is also elastic, allowing it to deform and return to its original shape, akin to a rubber band.
The elastic nature of the ice is what allows cracks and channels to form in the first place.
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On the other hand, the creeping nature of the ice helps channels inside the glacier to close again over time after the drainage has taken place. The size of the triangular mulen fractures on the surface remains unchanged for several years. Radar images show that although they change over time inside the glacier, they are still detectable years after their formation. This data also reveals that there is a network of cracks and channels, meaning that there's more than one way for the water to escape.
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And by the way, in this photo, the photos here very imaging here. Here's the lake right here. Right? Here's the a little darker there. There's your lake. So now, how is the melt water lifting the glaciers? Well, the researchers were able to see shadows along the cracks in some aerial photos. In some cases, the ice at the fracture surfaces have also shifted in height as if it'll raise more on one side of the mullen than on the other. So often times you get a crack in the ice, the water, as we just discussed, makes its way down to the base, but it's not a straight vertical. It it kind of wherever the fracture lines are, however the the planes of the ice crystals orientate themselves, it will the water will follow this, following the least the path of least resistance. And some of this could involve horizontal movement. And if you get a horizontal movement, you could get like a crack.
The largest shift is encountered directly in the lake, which is due to the enormous masses of water that have entered the cracks beneath the glacier and formed a subglacial lake there. Radar images from inside show that a blister has apparently formed on this lake beneath the ice pushing the glacier upwards at this point. Remember, okay, water has, fresh water, right? At 0 C has a a density that is lesser than at its coldest, which is 4C.
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This is for fresh water. So, and due to the nature of the ice molecules and the type of crystals they form as the water cools down to about zero, it expands. That's and most likely this expansion because it's pretty much going to be right at about zero. It's not going to be at four. It's going to be right about at zero. that is going probably helping to push the ice about and what's interesting is that even after more than 15 years after the first drainage the cracks are still visible on the surface.
So the researchers use very- they use satellite remote sensing data, use data from airborne surveys, they are able to see how the lake fills and drains with the pathways that the water took within the glacier visco elastic modeling, like viscosity enabled them to determine whether and how drainage paths close over time.
So the question that now is raised is have the frequent drainages forced the glacier system into a new state or can the system still return to a normal winter state in spite of these extreme amounts of water? That's an important question to ask. That is what they're working to try and get a handle on.
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In just 10 years, recurring patterns and regularity have developed in the drainage with massive and abrupt changes in meltwater inflow on a time scale of hours to days. That's pretty quick. These are extreme disturbances within the system and has not yet been investigated whether the glacial system can absorb this amount of water and is able to influence the drainage itself.
So why is this important? because it it provides data that can then utilize in incorporate integrate the cracks into ice sheet models and then examining researching how they form and influence the glacier overall.
So Alfred Vega institute researchers are working closely with scientists from TU Darnstat and the University of Stuttgart on the modeling Understanding and taking the behavior and effects of cracks in the glacier into account is particularly important when regarding the development of the lake at 79 degrees north latitude.
Due to the advancing warming of the atmosphere, the fracture surfaces have been occurring further and further up the slope. Ooh, this is critical. further and further up the slope impacting on an increasingly larger area of the glacier. So that does not bode well if you really think about it because that might you know in addition to you know the cracks and looking part of the ice. It can also facilitate the movement of the glacier itself possibly to the sea where possibly it calves off and goes into the ocean,
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79° north that's a bit up there. So, put in perspective, a point of Utiatvik, in Alaska, the furthest northerly point on the North American continent is at about 72 degrees north latitude. So, we're talking another 7 degrees. And so, that's going to be oh about 670 kilometers further north or so. So, that's that does have ramifications for the that part of the northern hemisphere and probably not going to be good. So something to keep an eye on because this does have major implications.
Freshwater input, loss of ice, what that means to albido and so on so forth. All things we've been discussing for years, but this is added to it. It's another area of concern. So there you have it. glacier at degrees north light on Greenland is cracking up and it's not a funny thing. Until next time, thank you for your time. END OF TRANSCRIPT
