Aslak Grinsted
@glaciology.net
Associate Professor at the Niels Bohr Institute, University of Copenhagen. Interested in ice, climate, sea level, and extreme events. 🧪 ❄️ 🌊 🌀 🥼 🌡️
Dad of two teen girls, and one toddler boy.
Also on mastodon here: @[email protected]
Dad of two teen girls, and one toddler boy.
Also on mastodon here: @[email protected]
I have built a cool little prototype ML algo that can estimate population density in 20m resolution from S2 imagery.
Here are 5 examples.
Row1: Sentinel-2. (input data)
Row2: population density from eurostat. (input data)
Row3: ML model population density. (output data)
Here are 5 examples.
Row1: Sentinel-2. (input data)
Row2: population density from eurostat. (input data)
Row3: ML model population density. (output data)
May 22, 2025 at 11:11 AM
I have built a cool little prototype ML algo that can estimate population density in 20m resolution from S2 imagery.
Here are 5 examples.
Row1: Sentinel-2. (input data)
Row2: population density from eurostat. (input data)
Row3: ML model population density. (output data)
Here are 5 examples.
Row1: Sentinel-2. (input data)
Row2: population density from eurostat. (input data)
Row3: ML model population density. (output data)
Why do these 2 numpy lines not give the same result? Aaargh!
data[range(1,3),range(1,3)].shape -> (2,)
data[1:3,1:3].shape -> (2,2)
I don't want the diagonal!
data[range(1,3),range(1,3)].shape -> (2,)
data[1:3,1:3].shape -> (2,2)
I don't want the diagonal!
May 21, 2025 at 6:28 PM
Why do these 2 numpy lines not give the same result? Aaargh!
data[range(1,3),range(1,3)].shape -> (2,)
data[1:3,1:3].shape -> (2,2)
I don't want the diagonal!
data[range(1,3),range(1,3)].shape -> (2,)
data[1:3,1:3].shape -> (2,2)
I don't want the diagonal!
Bedrock reached at the Ice coring on Müller ice cap (Axel Heiberg Island).
I bet that we would reach at 611m --- pretty close to the final 613m. (Bo guessed 612m so i didn't win).
I bet that we would reach at 611m --- pretty close to the final 613m. (Bo guessed 612m so i didn't win).
May 19, 2025 at 10:02 AM
Bedrock reached at the Ice coring on Müller ice cap (Axel Heiberg Island).
I bet that we would reach at 611m --- pretty close to the final 613m. (Bo guessed 612m so i didn't win).
I bet that we would reach at 611m --- pretty close to the final 613m. (Bo guessed 612m so i didn't win).
They got the EGRIP camp weather data flowing out of camp. alice.egrip.camp
May 14, 2025 at 2:24 PM
They got the EGRIP camp weather data flowing out of camp. alice.egrip.camp
I need a new circular saw and would like the batteries to be compatible with my other DeWalt tools. But i am wondering if i should jump ship to some non-US brand. Also - they apparently have extra high exposure to the tariff situation.
April 13, 2025 at 2:55 PM
I need a new circular saw and would like the batteries to be compatible with my other DeWalt tools. But i am wondering if i should jump ship to some non-US brand. Also - they apparently have extra high exposure to the tariff situation.
Loewe 1936: "... there is a strong evidence that the Greenlandic ice cap is not quickly decreasing today but in a nearly stationary condition".
Pretty impressive statement considering the sparse data at the time.
I'd love a pdf of that paper. Anybody?
www.buchfreund.de/de/d/p/79453...
Pretty impressive statement considering the sparse data at the time.
I'd love a pdf of that paper. Anybody?
www.buchfreund.de/de/d/p/79453...
February 10, 2025 at 2:26 PM
Loewe 1936: "... there is a strong evidence that the Greenlandic ice cap is not quickly decreasing today but in a nearly stationary condition".
Pretty impressive statement considering the sparse data at the time.
I'd love a pdf of that paper. Anybody?
www.buchfreund.de/de/d/p/79453...
Pretty impressive statement considering the sparse data at the time.
I'd love a pdf of that paper. Anybody?
www.buchfreund.de/de/d/p/79453...
End of an era. The final Symposium of the EastGRIP project.
January 27, 2025 at 2:41 PM
End of an era. The final Symposium of the EastGRIP project.
Here, I've exaggerated the contrast of a Sentinel-2 median image from the same region (Sharffenbergbotnen). Notice the clear layering. The youngest blue-ice appear more brownish. I wonder why? We believe this valley to be mostly holocene ice.
January 9, 2025 at 7:44 AM
Here, I've exaggerated the contrast of a Sentinel-2 median image from the same region (Sharffenbergbotnen). Notice the clear layering. The youngest blue-ice appear more brownish. I wonder why? We believe this valley to be mostly holocene ice.
Blue ice areas are a source of ancient ice. So, you can potentially use them to get a horizontal ice core. Here's a photo of a very clear layer that i interpret as an isochrone. Maybe this layer was caused by volcanic eruption. The challenge is how to date the ice.
January 8, 2025 at 11:39 AM
Blue ice areas are a source of ancient ice. So, you can potentially use them to get a horizontal ice core. Here's a photo of a very clear layer that i interpret as an isochrone. Maybe this layer was caused by volcanic eruption. The challenge is how to date the ice.
Many electrical wood working tools work great on ice. I've used band saws, circular saws, chainsaws, hand drills, router, and planer.
Here's me 20years ago. Cutting a blue ice sample with a chainsaw.
Here's me 20years ago. Cutting a blue ice sample with a chainsaw.
January 8, 2025 at 11:33 AM
Many electrical wood working tools work great on ice. I've used band saws, circular saws, chainsaws, hand drills, router, and planer.
Here's me 20years ago. Cutting a blue ice sample with a chainsaw.
Here's me 20years ago. Cutting a blue ice sample with a chainsaw.
Organizing some old fieldwork photos using immich. Here's a nice black "dragon" shaped stripe in Scharffenbergbotnen, Heimefrontfjella, Antarctica.
January 3, 2025 at 3:42 PM
Organizing some old fieldwork photos using immich. Here's a nice black "dragon" shaped stripe in Scharffenbergbotnen, Heimefrontfjella, Antarctica.
In other images we can see sediments being flushed into the fjord.
Soon after we can see sea ice forming. Probably because fresh water freezes more easily. Later it spreads out and fills almost the entire fjord.
Soon after we can see sea ice forming. Probably because fresh water freezes more easily. Later it spreads out and fills almost the entire fjord.
December 12, 2024 at 12:19 PM
In other images we can see sediments being flushed into the fjord.
Soon after we can see sea ice forming. Probably because fresh water freezes more easily. Later it spreads out and fills almost the entire fjord.
Soon after we can see sea ice forming. Probably because fresh water freezes more easily. Later it spreads out and fills almost the entire fjord.
Here's some additional media. A timelapse of the lake level dropping as seen in S2.
new press release: science.ku.dk/english/pres...
+a video of the past events published in 2017: www.youtube.com/watch?v=xDH5...
5/
new press release: science.ku.dk/english/pres...
+a video of the past events published in 2017: www.youtube.com/watch?v=xDH5...
5/
December 12, 2024 at 12:09 PM
Here's some additional media. A timelapse of the lake level dropping as seen in S2.
new press release: science.ku.dk/english/pres...
+a video of the past events published in 2017: www.youtube.com/watch?v=xDH5...
5/
new press release: science.ku.dk/english/pres...
+a video of the past events published in 2017: www.youtube.com/watch?v=xDH5...
5/
ICESat-2 gave us a nice record of the lake filling prior the recent outburst flood.
We know the longer historical context from a 2017 study. There were no good images of the prior GLOFs as they occurred during the polar night. So, this is the first time we can estimate the discharge. 4/x
We know the longer historical context from a 2017 study. There were no good images of the prior GLOFs as they occurred during the polar night. So, this is the first time we can estimate the discharge. 4/x
December 12, 2024 at 12:09 PM
ICESat-2 gave us a nice record of the lake filling prior the recent outburst flood.
We know the longer historical context from a 2017 study. There were no good images of the prior GLOFs as they occurred during the polar night. So, this is the first time we can estimate the discharge. 4/x
We know the longer historical context from a 2017 study. There were no good images of the prior GLOFs as they occurred during the polar night. So, this is the first time we can estimate the discharge. 4/x
The peak discharge corresponds to 7200 m3/s. That is ~2.5x Niagara falls in the tourist season.
There is a big potential energy release as the water runs to sea level. The max daily release was ~46 GW.
3/x
There is a big potential energy release as the water runs to sea level. The max daily release was ~46 GW.
3/x
December 12, 2024 at 12:09 PM
The peak discharge corresponds to 7200 m3/s. That is ~2.5x Niagara falls in the tourist season.
There is a big potential energy release as the water runs to sea level. The max daily release was ~46 GW.
3/x
There is a big potential energy release as the water runs to sea level. The max daily release was ~46 GW.
3/x
From sentinel-2 images and an elevation model I estimate the daily lake level. New satellites and good weather made that possible.
V= 3.4km3 (for comparison the annual water consumption of Denmark is ~1km3, and the total volume of all humans is about 0.5km3)
2/x
V= 3.4km3 (for comparison the annual water consumption of Denmark is ~1km3, and the total volume of all humans is about 0.5km3)
2/x
December 12, 2024 at 12:09 PM
From sentinel-2 images and an elevation model I estimate the daily lake level. New satellites and good weather made that possible.
V= 3.4km3 (for comparison the annual water consumption of Denmark is ~1km3, and the total volume of all humans is about 0.5km3)
2/x
V= 3.4km3 (for comparison the annual water consumption of Denmark is ~1km3, and the total volume of all humans is about 0.5km3)
2/x
A new gigantic outburst flood from Catalina lake in East Greenland [Catalinadal, Renland, Scoresbysund].
total volume: 3.4 km3
peak discharge: ~7200 m3/s
top-10 #GLOF in terms of both numbers.
previous outburst 2013
I'm sending out a press release today about it.
🧪❄️ 🥼❄️
1/x
total volume: 3.4 km3
peak discharge: ~7200 m3/s
top-10 #GLOF in terms of both numbers.
previous outburst 2013
I'm sending out a press release today about it.
🧪❄️ 🥼❄️
1/x
December 12, 2024 at 12:09 PM
A new gigantic outburst flood from Catalina lake in East Greenland [Catalinadal, Renland, Scoresbysund].
total volume: 3.4 km3
peak discharge: ~7200 m3/s
top-10 #GLOF in terms of both numbers.
previous outburst 2013
I'm sending out a press release today about it.
🧪❄️ 🥼❄️
1/x
total volume: 3.4 km3
peak discharge: ~7200 m3/s
top-10 #GLOF in terms of both numbers.
previous outburst 2013
I'm sending out a press release today about it.
🧪❄️ 🥼❄️
1/x
Digging a particularly deep toilet hole at EGRIP.
December 10, 2024 at 9:57 PM
Digging a particularly deep toilet hole at EGRIP.
Remote sensing sea ice experts: Is this fresh sea ice? (It was a plume of sediment rich freshwater a few days prior)
November 7, 2024 at 7:47 PM
Remote sensing sea ice experts: Is this fresh sea ice? (It was a plume of sediment rich freshwater a few days prior)
Trying to show the scale of a lake using blender + blendergis + sentinel2 + arcticdem and a model of the eiffeltower. Steep learning curve - but fun.
I am considering using the golden gate bridge or the statue of liberty instead.
I am considering using the golden gate bridge or the statue of liberty instead.
November 3, 2024 at 12:02 PM
Trying to show the scale of a lake using blender + blendergis + sentinel2 + arcticdem and a model of the eiffeltower. Steep learning curve - but fun.
I am considering using the golden gate bridge or the statue of liberty instead.
I am considering using the golden gate bridge or the statue of liberty instead.
Half of all voters need to read some scifi dystopias to learn about which futures to avoid. -maybe Octavia E. Butlers Parable of the Sower.
October 22, 2024 at 6:17 PM
Half of all voters need to read some scifi dystopias to learn about which futures to avoid. -maybe Octavia E. Butlers Parable of the Sower.
The latest forecast has shifted the track and the surge a little north. Better for Rotunda
https://cera.coastalrisk.live/
https://cera.coastalrisk.live/
October 9, 2024 at 10:19 AM
The latest forecast has shifted the track and the surge a little north. Better for Rotunda
https://cera.coastalrisk.live/
https://cera.coastalrisk.live/
September 25, 2024 at 4:01 PM
It would be great if Jupyter notebooks had a cell type for tabular data.
I'd like something better than this...
I'd like something better than this...
September 24, 2024 at 9:08 AM
It would be great if Jupyter notebooks had a cell type for tabular data.
I'd like something better than this...
I'd like something better than this...