British Antarctic Survey on the Brunt Ice Shelf calving
As a follow-up to our article about the Brunt Ice Shelf calving, the British Antarctic Survey have posted on their own website. Their report states:
A huge iceberg (1270 km²) the size of the county of Bedfordshire has broken off the 150-m thick Brunt Ice Shelf, almost a decade after scientists at British Antarctic Survey (BAS) first detected growth of vast cracks in the ice.
The Brunt Ice Shelf is the location of British Antarctic Survey’s (BAS) Halley Research Station. BAS glaciologists, who have been expecting a big calving event for at least a decade, say that the research station is unlikely to be affected by the current calving. The 12-person team working at the station left mid-February by BAS Twin Otter aircraft. The station is now closed for the Antarctic winter.
The glaciological structure of this vast floating ice shelf is complex, and the impact of ‘calving’ events is unpredictable. In 2016, BAS took the precaution of relocating Halley Research Station 32 km inland to avoid the paths of ‘Chasm 1’ and ‘Halloween Crack’.
Since 2017, staff have been deployed to the station only during the Antarctic summer, because during the dark winter months evacuation would be difficult. ‘Chasm 1’ and ‘Halloween Crack’ have not grown in the last 18 months.
Professor Dame Jane Francis, Director of British Antarctic Survey says:
“Our teams at BAS have been prepared for the calving of an iceberg from Brunt Ice Shelf for years. We monitor the ice shelf daily using an automated network of high-precision GPS instruments that surround the station, these measure how the ice shelf is deforming and moving. We also use satellite images from ESA, NASA and the German satellite TerraSAR-X. All the data are sent back to Cambridge for analysis, so we know what’s happening even in the Antarctic winter, when there are no staff on the station, it’s pitch black, and the temperature falls below minus 50 degrees C (or -58F).
“Over coming weeks or months, the iceberg may move away; or it could run aground and remain close to Brunt Ice Shelf. Halley Station is located inland of all the active chasms, on the part of the ice shelf that remains connected to the continent. Our network of GPS instruments will give us early warning if the calving of this iceberg causes changes in the ice around our station.”
Simon Garrod, Director of Operations at British Antarctic Survey adds:
“This is a dynamic situation. Four years ago we moved Halley Research Station inland to ensure that it would not be carried away when an iceberg eventually formed. That was a wise decision. Our job now is to keep a close eye on the situation and assess any potential impact of the present calving on the remaining ice shelf. We continuously review our contingency plans to ensure the safety of our staff, protect our research station, and maintain the delivery of the science we undertake at Halley.”
About Halley VI
Halley VI Research Station is an internationally important platform for, atmospheric and space weather observation in a climate-sensitive zone. In 2013, the station attained the World Meteorological Organization (WMO) Global Atmosphere Watch (GAW) Global station status, becoming the 29th in the world and 3rd in Antarctica.
Halley VI Research Station sits on Antarctica’s up to 150–m thick Brunt Ice Shelf. This floating ice shelf flows at a rate of up to 2 km per year west towards the sea where, at irregular intervals, it calves off as icebergs.
Long-term monitoring of the natural changes that occur in the ice shelf has revealed changes, including growth of a recently-formed chasm, the North Rift. Halley VI Research Station has been unoccupied during the last four winters because of the complex and unpredictable glaciological situation.
Change in the ice at Halley is a natural process and there is no connection to the calving events seen on Larsen C Ice Shelf, and no evidence that climate change has played a significant role. (Emphasis added)
During the 2016-17 Antarctic Summer season (Nov-March), in anticipation of calving, the eight station modules were uncoupled and transported by tractor to a safer location upstream of Chasm-1.
Over the summer 18/19, BAS installed an autonomous power generation and management system – Halley Automation project – which provides a suite of scientific instruments with power even when we have no staff at the station. This system has proved effective in running through more than eight months of darkness, extreme cold, high winds and blowing snow and delivering important data back to UK.
There have been six Halley research stations on the Brunt Ice Shelf since 1956.
About Chasm 1
In 2012, satellite monitoring revealed the first signs of change in a chasm (Chasm 1) that had lain dormant for at least 35 years. This change had implications for the operation of Halley VI Research Station. In the 2015/16 field season, glaciologists used ice penetrating radar technologies to ‘ground truth’ satellite images and to calculate the most likely path and speed of Chasm 1. Chasm 1 grew up until 2019 but has not moved for the past 18 months. There is now 2 km of ice holding this iceberg in place.
About Halloween Crack
In October 2016, a new crack was detected some 17 km to the north of the research station across the route sometimes used to resupply Halley. The ‘Halloween Crack’ continues to widen and a second large iceberg may calve to the north’. The tip of Halloween Crack is also currently static.
About North Rift Crack
In November 2020, a new chasm, known as the North Rift opened and started extending towards Brunt-Stancomb Chasm.
Animation of the Brunt Ice shelf separation following the calving along the North Rift chasm
The Brunt Ice Shelf is probably the most closely monitored ice shelf on Earth. A network of 16 GPS instruments measure the deformation of the ice and report this back on a daily basis. European Space Agency satellite imagery (Sentinel 2), TerraSAR-X, NASA Worldview satellite images, US Landsat 8 images, ground penetrating radar, and on-site drone footage have been critical in providing the basis for early warning of changes to the Brunt Ice Shelf. These data have provided science teams with a number of ways to measure the width of Chasm 1 and changes to the Halloween Crack and North Rift crack, with very high precision. In addition, scientists have used computer models and bathymetric maps to predict how close the ice shelf was to calving.
About Halley science
- Ozone measurements that have been made continuously at Halley since 1956 (which led to the discovery of the ozone hole in 1985, and since that time, its slow progress towards recovery)
- Monitoring of space weather undertaken at Halley contributes to the Space Environment Impacts Expert Group that provides advice to UK Government on the impact of space weather on UK infrastructure and business.
See more here: www.bas.ac.uk
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Jerry Krause
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Hi PSI Readers.
This comment is to direct your attention to one statement of this press comment and to one which was not mentioned
I read: “This system has proved effective in running through more than eight months of darkness.”
Long ago in elementary school I had been taught the within the ‘polar circles’ the sun never rises for 6 months and never sets for 6 months.
Next I read: “All the data are sent back to Cambridge for analysis, so we know what’s happening even in the Antarctic winter, when there are no staff on the station, it’s pitch black, and the temperature falls below minus 50 degrees C (or -58F).”
But I don’t read that ice must be reforming at the surface of the ocean to reconnect the ‘iceberg’ along a crack to the ice shelf. Admittedly this ice connection may be only a few meters thick relative to the 150m thick ice shelf and iceberg but a fact is the iceberg is not at all like the iceberg which sank the Titanic. Which was floating free in a ocean which was ice free.
I ask how thick a ‘new’ ice layer (connection) become during a decade when a noticeable crack does not grow wider. We should not forget we are dealing with huge masses which there is no ‘natural’ force which could. move the iceberg “several hundred metres in a few hours on the morning of 26th Feb, releasing it from the rest of floating ice shelf.”
We should acknowledge that the solid ice connection between the ‘iceberg’ and the main ice shelf had become stretched like a rubber band until it broke. Like we can stretch a rubber band until it breaks. So the ‘iceberg’ does not move several hundred metres in a few hours. The stretched connecting ice snaps back to the iceberg and to the ice shelf along a newly formed wide ‘crack’.
This may seem weird and unbelievable; but let anyone give another explanation what natural force could move the iceberg several hundred metres and then suddenly stop moving the iceberg after a few hours.
Have a good day, Jerry
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Tom O
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I noticed they also mentioned that the iceberg may not float away but ground. If you have deformation of the ground beneath the ice, and the ice is firmly grounded on it, I can visualize that as the source of a force great enough to cause the movement. The question would be, though, was the crack several hundred meters along its length, of just at the widest spot, which might be located near the grounded spot where the ground moved.
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Jerry Krause
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Hi Tom O,
If I understand your comment correctly, when you propose “the ground moved”.you seem to propose there could have been a seismic event which would have been noticed ‘around the world’. Please clarify.
Have a good day, Jerry.
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Matth
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Hi Young Jerry.
Halley VI Research Station sits on Antarctica’s up to 150–m thick Brunt Ice Shelf. This floating ice shelf flows at a rate of up to 2 km per year west towards the sea where, at irregular intervals, it calves off as icebergs.
This is the dynamic process I failed to acknowledge in comments on Andy Rowlands article on this event. Solid Ice flowing at two Kilometers per year is surely humming along.
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Jerry Krause
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Hi MattH,
And as I seem to remember that that this moving ice shelf is being ‘fed’ (pushed?) by glaciers sliding off the slopes of the Continent.
Have a good day, Jerry
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Jerry Krause
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Hi Tom O,
Amazing what you can find with so little effort. And I am guilty of not usually making the effort. Maybe I will eventually learn.
Chasm ! Googled it and soon found: “The Brunt shelf has been monitored by glaciologists for decades and is constantly changing. Early maps from the 1970s indicate that the ice shelf used to be a mass of small icebergs welded together by sea ice.”
And one can see what Chasm 1 looked like int 2017. And read about the Mac Donald rumple where thick ice shelves become anchored on the ground of of the shallow ocean bottom.
You made a good comment which alerted me to reported descriptions of what has happened when the grounding has actually occurred. And I can read about the observations being made and readily accept the observations and understanding by scientists who still believe in the wrong idea of the Greenhouse Effect of atmospheric carbon dioxide and other GH gases.
Please repeat in every one of your comments that the measued air temperature has never been lower than the measured air’s due point temperature measured at the same location and time. And go to the RAWS (Remote Automated Weather Stations) where at many of the more than 1000 sites report for each hour: the air temperature (at about 1.5m above the surface) , the fuel temperature (at about 1ft above the surface0 and the air’s dew point temperature (at about 1.5m above the surface).
Have a good day, Jerry
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Wisen
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Any chance of getting surface aluminum levels from the region? There have been reports of elevated aluminum levels in surface snow far above normal background. This would be from atmospheric deposits, and possibly from aerosols released from airplanes. Excess aluminum deposits would scatter light within the ice, increasing its flow rate and possibly causing fissures in seemingly unrelated areas. Should the UV and solar radiation be high enough, what would be the possibility of the aluminum particles reverberating? I’m not an expert in that area, but frequencies in the microwave range would heat the water molecules just like the microwave oven. Could this action be triggered by lasers or wifi band signaling? I have no idea if this is even possible, but the elevated aluminum sticks out as something to be concerned about to me.
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Pavel Moore
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Jerry
You wrote:
“I read: “This system has proved effective in running through more than eight months of darkness.”
May I suggest you re-read that whole paragraph you quoted from again. It states that “Over the summer 18/19, BAS installed an autonomous power generation and management system – Halley Automation project …” for use during the un-attended staffing of the site from the winter of 2019 up, and to, the winter of the year it was written i.e. 2 and a bit winters!
I am also curious, though, as to why no one attempts to comment about the effects that diurnal tides and storm surges have on the elasticity of the floating ice close to its mainland grounding point. This has been likened to the continuous bending of sheet metal — it will eventually fracture.
Pavel
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Jerry Krause
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Hi Pavel,
Thank you for your comment; as I have written that it encourages me to learn that someone is reading what I have written. So I expect this comment might encourage you. For it is good to agree or disagree as the case may be. I wrote about “more than eight months of darkness’ because there is no location on this planet that there are 8 months of continuous darkness.
So I hope this is not what you are questioning. It is true that the British vacate their stations for 8 months because I read it was because it was not safe remove the personnel in darkness. And a fact is that the length of daylight is quite brief during the month before no sunrise for 6 months and the month after the first sunrise after the 6 months of darkness.
Now relative to you 2nd paragraph, there are more factors than what you mentioned that are seldom mentioned. First, I do not deny the existence of diurnal tidal forces which, during a 24hr period first full one way and then 12hr later pull the opposite direction in the polar regions. But during the polar winter I doubt if the gravity of the sun has a significant influence but the moon does during the period a little before and after and during its Full Moon phase. Hence, this is a variable influence as are the storm surges. But there is only one constant force pulling the ice shelf away from the pull and it is the centrifugal effect of the rotating Earth (about which I have commented before).
You wrote “the elasticity of the floating ice close to its mainland grounding point.” the elasticity of the ice shelf near where it grounded is not the location where the ice shelf eventually ‘fractures’. Beside, according to what I read, the ice shelf not totally anchored to its grounding point, it shoved away from the continent by glaciers sliding down the steep slopes of the continent and the piling upward by these glaciers snow and ice is what forms the very thick ice shelf.of variable thickness. And I need to ask: Is your sheet metal even 30 meters thick.
My idea of the elasticity of ice was because I ‘Followed the Mosaic Progect of Arctic Ocean where the ice thickness was maybe mostly less than say 5 meters. Frequently cracks of limited lengths and very limited widths (leads) would form. And I could only image one possibility to explain these ‘observed’ leads. So I imagined that the ice sheet was being stretched logically as the ice floe in which an iceberger moved closer to and away from the North Pole by variable NATURAL factors. Then I knocked an 3/4in cross-section of an about 6in brand off a wall and it split apart and there was only a 1in section that could be fight tightly together. And the width of the the crack on one side of the cross-section was more the 1/4in. Obviously the ‘solid’ wood had remained elastically stretched this much for years and it took being dropped to relieve the stress of the elastic stretch.
Thanks again. This time for giving me opportunity to share my personal experiences.
Have a good day, Jerry
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