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Jonathan Amos

@jcdamos.bsky.social
174 followers 106 following 69 posts

Journalist. Former BBC Science Correspondent. Way too interested in icebergs for my own good.

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Jonathan Amos @jcdamos.bsky.social · 12/04/2026
Will I ever see D15a ever go walkabout, or will it stick in the mud for decades also?
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Jonathan Amos @jcdamos.bsky.social · 12/04/2026
I'm reasonably convinced now that Iceberg A23a has completely collapsed. The USNIC is no longer tracking a berg of that name. But A23k (also not listed) does however lumber on, albeit in a disheveled state. This view is from Thursday (9 April) NOAA-21 VIIRS. usicecenter.gov/Products/Ant...
9/4/26 Iceberg A23k - NOAA-21 VIIRS
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Jonathan Amos @jcdamos.bsky.social · 03/04/2026
End days for Iceberg A23. The two largest remaining fragments - A and K - had major blowouts on or just after the 28th of March. The largest chunks are ~50 sq km. A23 calved from the Filchner-Ronne Ice Shelf in 1986. Quite the journey it's had over four decades.
2 April. A23k after fragmentation event (Nasa)2 April. A23a after fragmentation event (Nasa)
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Jonathan Amos @jcdamos.bsky.social · 26/03/2026
The last two big fragments of the once mighty A23 iceberg. The US National Ice Center calls the bottom-left object A23k and the top-right, A23a. Its latest report (20/3/26) said both were about 140 sq km. Latitude is roughly 50 deg S.
Image by Nasa/Terra/Modis 26/3/2026
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Jonathan Amos @jcdamos.bsky.social · 17/02/2026
Iceberg A23a today (17 Feb). A totally clear sky. Utterly stunning. Still refusing to die. Still 500 sq km in area. Image from the Modis instrument on the venerable Aqua satellite, another oldie that's still plugging away.
Iceberg A23a, 17 Feb 2026, Aqua/Modis
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Jonathan Amos @jcdamos.bsky.social · 16/01/2026
These subtle ripples have revealed the presence of thousands of previously unknown hills, valleys, ridges and ancient river systems. New paper in Science Magazine from Helen Ockenden et al. www.science.org/doi/10.1126/...
science.org
Complex mesoscale landscapes beneath Antarctica mapped from space
The landscape shrouded by the Antarctic Ice Sheet provides important insights into its history and influences the ice response to climate forcing. However, knowledge of this critical boundary has depe...
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Jonathan Amos @jcdamos.bsky.social · 16/01/2026
The landscape hidden beneath Antarctica's ice sheet has been mapped from space for the first time. Scientists used hi‑res satellite observations to track how the continent’s frozen surface bunches and dips as it moves over the rugged rock bed below. www.bbc.co.uk/news/article...
bbc.co.uk
New map reveals landscape beneath Antarctica in unprecedented detail
Scientists believe the map could shed light on how Antarctica's vast ice sheet will respond to climate change.
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Paul Voosen @voosen.me · 14/01/2026
A small silver lining: Yes, NASA and NOAA did not do briefings for their global temp data sets released today. And they certainly do not emphasize the human causes. But they *did* release them. The work is still happening. data.giss.nasa.gov/gistemp/grap... www.ncei.noaa.gov/access/monit...
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Prof Michael Meredith 🌊🧪🥼❄️ @oceanandice.bsky.social · 14/01/2026
🌊❄️ When Antarctic glaciers collapse into the sea, they can trigger huge underwater tsunamis that mix the ocean, affecting ice loss, climate and ecosystems. The project I lead on this is now in the field and featured on Sky News: news.sky.com/story/underw... #Antarctic #OceanMixing #ClimateScience
news.sky.com
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Jonathan Amos @jcdamos.bsky.social · 13/01/2026
One big paddling pool becomes three. Today's view of iceberg A23a (left) and a view from the end of December (right). Notice how the raised rim effect, holding in surface meltwater, has re-established on all three main segments of the broken berg. A23a is turning to slush puppie.
NASA Modis
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Jonathan Amos @jcdamos.bsky.social · 12/01/2026
💥 Boom! And it's just happened. The huge volumes of meltwater that had collected on the surface of iceberg A23a have triggered a massive and catastrophic hydrofracture event. Much of the berg has turned to mush. Three major segments remain, the largest about 500 sq km.
NASA Aqua Modis 11 January
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Jonathan Amos @jcdamos.bsky.social · 29/12/2025
Want to see an iceberg turn to mush? What remains of iceberg A23a (<1,000 sq km) is about to experience death by hydrofracture. Look at all the meltwater sitting atop the berg. The whole thing could just fall apart any day now.
NOAA 20 / VIIRS - Iceberg A23a viewed on 24 December 2025
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Rob Larter @polarrobs.bsky.social · 04/11/2025
I haven't heard about the disagreements. The ice was sitting on an ice plain - a very flat bed with low basal drag. These are present beneath the downstream parts of many Antarctic glaciers where the sediment they transport has built a depositional body known as a grounding zone wedge.
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Jonathan Amos @jcdamos.bsky.social · 03/11/2025
And if you want a longer read, my old mate Mark Poynting has a great write-up on Auntie Beeb. www.bbc.co.uk/news/article...
bbc.co.uk
Rapid Antarctic glacier retreat sparks scientific 'whodunnit'
A new study suggests that changes to Hektoria Glacier are unprecedented - but not all scientists agree.
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Jonathan Amos @jcdamos.bsky.social · 03/11/2025
"Such records are vital for distinguishing between rapid grounding-line retreat, as is reported to have occurred at Hektoria Glacier, versus the retreat of a floating ice margin through “conventional” iceberg calving processes," says polar SAR specialist Frazer Christie at Airbus Defence and Space.
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Jonathan Amos @jcdamos.bsky.social · 03/11/2025
But the paper has caused a stir because there is wide disagreement in the glaciology community about precisely where Hektoria had been fully grounded on bedrock due to a lack of high-accuracy satellite records.
NASA/AQUA/MODIS
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Jonathan Amos @jcdamos.bsky.social · 03/11/2025
Swansea Uni co-author @adrianluckman.bsky.social put this Sentinel-1 movie together. "Although the paleo record indicates some very rapid retreats in the past, the pace of retreat of Hektoria Glacier and its neighbours is unprecedented in the observational record," Adrian says.
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Jonathan Amos @jcdamos.bsky.social · 03/11/2025
Ochwat and Colorado/Boulder co-author Ted Scambos described the lightning-fast fracturing as “shocking” and warned that the retreat “changes what’s possible” for important glaciers elsewhere on the continent. www.nature.com/articles/s41...
nature.com
Record grounded glacier retreat caused by an ice plain calving process - Nature Geoscience
An Antarctic glacier retreated after the loss of landfast ice at a peak rate almost an order of magnitude faster than previously recorded because of buoyancy-driven ice calving, according to an analys...
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Jonathan Amos @jcdamos.bsky.social · 03/11/2025
Hektoria lost ~25km in 15 months, with 8.2km fragmenting in just the Nov/Dec of 2022. Naomi Ochwat et al point to a particular vulnerability: an "ice plain" - a big section of glacier ice sitting on flat seabed rock that suddenly goes afloat, spitting off icebergs like crazy.
Satellite images of the terminus of Hektoria glacier taken on 26 October 2022 (left) and 23 February 2023 (Copernicus/ESA/A.Luckman/Swansea University)
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Jonathan Amos @jcdamos.bsky.social · 03/11/2025
A fascinating paper in @NatureGeosci that has already sparked considerable debate in the ice community. It's the super-fast withdrawal of Hektoria Glacier on the eastern side of the Antarctic Peninsula in 2022/23. Words by me in @newscientist.com www.newscientist.com/article/2502...
newscientist.com
Antarctic glacier's alarming retreat is the fastest ever seen
Hektoria glacier on the Antarctic Peninsula retreated 25 kilometres in just 15 months. Its rapid melt could have implications for other glaciers and the rate of sea level rise
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Roland Pease @peaseroland.bsky.social · 25/10/2025
Speed reading "Science under Siege" - ahead of next week's recording of BBC Science in Action, where co-author @michaelemann.bsky.social joins a panel on the front line of the current assault on science, to answer what can be done. An appropriate topic for the last edition of the 60yr old series.
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Jonathan Amos @jcdamos.bsky.social · 04/10/2025
Ooops! It's happened again. The remnants of iceberg A23a have been caught on another Taylor Column, this time above the NorthWest Georgia Rise to the north of South Georgia BOT. The fragments have spun around and around for more than a month now.
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Jonathan Amos @jcdamos.bsky.social · 02/09/2025
Fab first data from the UK-supplied Microwave Sounder on the new Metop weather satellite. MWS combines obs from the old MHS & AMSU instruments. MWS measures the temperature and water content sitting at different altitudes. Fundamental data needed by computer models' for medium range forecasts.
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Jonathan Amos @jcdamos.bsky.social · 30/08/2025
Really clear view today of Iceberg A23a's big fragmentation event. Going back through the data, I think it happened on the 25th/26th. Image from NASA/Terra/Modis. Each new fragment is probably big enough to get a US National Ice Center designation. Likely A23g, A23h and A23i.
NASA Terra/Modis 30/8/25
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Jonathan Amos @jcdamos.bsky.social · 29/08/2025
OK, the US National Ice Center was being a bit more generous than me. It logged A23a at 2,371 sq km. For comparison, the current title holder of the "world's biggest iceberg" is A15a at 3,070 sq km, grounded in the Amery Sea off East Antarctica.
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Jonathan Amos @jcdamos.bsky.social · 29/08/2025
🚨🚨🚨Boom! Iceberg A23a looks to have undergone a major fragmentation event in the past 24 hours. I count at least three "daughter" bergs (g, h and i ?). Further satellite imagery will confirm. The last intact measurement I made was ~2,250 sq km. @bas.ac.uk
Iceberg A23a Nasa Terra/Modis 28/8/25
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Jonathan Amos @jcdamos.bsky.social · 15/07/2025
Iceberg A23a update. It's lost another couple of large chunks in the past few days. Are we getting close to a major fragmentation event? Likely so.
Polar View Sentinel-1
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Jonathan Amos @jcdamos.bsky.social · 07/07/2025
In case you were wondering... Iceberg A23a seen cruising around South Georgia today by Meteosat 12. The old berg still has an area of 2,846 sq km.
Iceberg A23a on 7/7/25 Eumetsat/Meteosat 12
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Jonathan Amos @jcdamos.bsky.social · 15/06/2025
Iceberg D15a, grounded in the Amery Sea, is now officially "the world's biggest iceberg".
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Jonathan Amos @jcdamos.bsky.social · 15/06/2025
Sentinel-1 has finally got a clear view of iceberg A23a (13/6/25). The berg is much diminished as it skirts around South Georgia. And the US National Ice Center has updated its stats: A23a is now only the world's second biggest berg at 829.79 sqNM, or 2846,11 sqKM.
PolarView 13/5/25
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Jonathan Amos @jcdamos.bsky.social · 04/06/2025
You can see the original grounded position in this BBC map. The berg is following the expected track, riding the prevailing current and hugging the continental shelf. It could always ground again. But if not, it should sweep around SG and go north.
Grounded position of iceberg A23a in early March off the coast of South Georgia
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Jonathan Amos @jcdamos.bsky.social · 04/06/2025
The movement of iceberg A23a over the past seven days. It's moved about 80km to the southeast of the position where it grounded off the coast of South Georgia in early March. Zoomed in animation from Meteosat-12.
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Jonathan Amos @jcdamos.bsky.social · 01/06/2025
And I'm pretty sure now that A23a is no longer the "World's Biggest Iceberg". D15a is larger in my view. But only the US National Ice Center can make that determination and its listing doesn't yet reflect this.
Nasa Worldview measurement of iceberg A23a
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Jonathan Amos @jcdamos.bsky.social · 01/06/2025
Somebody's got itchy feet! Iceberg A23a has moved in the past couple of days. It grounded close to South Georgia back at the beginning of March. But the erosion and melting since then has clearly allowed it to break free. Does it now reground or sweep off around the island?
Nasa Worldview image of iceberg A23a
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Mark Parrington @mparrington.bsky.social · 30/05/2025
Latest #CopernicusAtmosphere AOD forecast (from 30/05 00 UTC) shows smoke plume from devastating (&growing) Canadian #wildfires continuing across the Atlantic with hazy skies for Europe over next few days atmosphere.copernicus.eu/charts/packa... @copernicusecmwf.bsky.social @ecmwf.int
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Jonathan Amos @jcdamos.bsky.social · 30/05/2025
With days shortening at South Georgia (it's about 8 hours from sunrise to sunset), optical satellite coverage in the region is getting more restricted. Not so for Meteosat, which images the Europe/Africa hemisphere regardless of season. Hence we get a few views of iceberg A23a. Still grounded.
Meteosat view of South Georgia and iceberg A23a. 30/5/25
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Prof Ian Hall @ianhall.bsky.social · 08/05/2025
I can't shake the feeling that these ideas are getting far more attention than their credibility and maturity warrant! Cutting global greenhouse gas emissions as soon as possible is the key to tackling global warming. www.thetimes.com/uk/science/a...
thetimes.com
Hope to halt climate change by thickening Arctic sea ice
The government has outlined how it will spend £57 million on research on geo-engineering projects designed to cool the planet
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Nagissa Mahmoudi @nagissa.bsky.social · 08/05/2025
How little we’ve seen: A visual coverage estimate of the deep seafloor | Science Advances www.science.org/doi/10.1126/...
science.org
How little we’ve seen: A visual coverage estimate of the deep seafloor
In decades of deep-sea exploration, humans have observed only 0.001% of the deep seafloor, leaving 66% of planet Earth unseen.
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Jonathan Amos @jcdamos.bsky.social · 06/05/2025
There was a spectacular view of iceberg A23a on 3 May. Clear skies over the berg and South Georgia. By my measurement, A23a is no longer the world's biggest iceberg. At ~2850 sq km, it's now bested by D15a - but only just. The US National Ice Center will be the final judge on the matter.
Iceberg A23a on 3 May. Copernicus / Sentinel-3
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Rob Larter @polarrobs.bsky.social · 02/05/2025
This is almost unbelievable. It's now May and there is still virtually no new sea ice forming in the Bellingshausen Sea (lower left region in image). Image showing sea ice concentration derived from AMSR satellite data is by Institute of Environmental Physics, University of Bremen, Germany.
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British Antarctic Survey 🐧 @bas.ac.uk · 25/04/2025
The Penguin Book of Penguins! Coming later this year: a beautifully illustrated book about the world’s most beloved bird, written by British Antarctic Survey’s Peter Fretwell @ptfretwell.bsky.social What better day to reveal the cover the #WorldPenguinDay? ⬇️
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Jonathan Amos @jcdamos.bsky.social · 24/04/2025
Everybody loves a good iceberg story, as @helen-amanda.bsky.social keeps telling me.
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Jonathan Amos @jcdamos.bsky.social · 24/04/2025
And see this version of the story from my old BBC pals Georgina Rannard and Mark Poynting because it’s got some great graphical work from the ever excellent Erwan Rivault www.bbc.co.uk/news/article...
bbc.co.uk
Iceberg tracks found off UK coast could shed light on Antarctica
Deep tracks gouged in the seafloor off the coast of Scotland could help us understand Antarctica today.
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James Kirkham @jdkirkham.bsky.social · 24/04/2025
Icebergs? The size of a city? 90 miles from the UK? Must be a joke, right? No! Our new paper in @natcomms.nature.com shows massive tabular icebergs broke off the UK in the last ice age before the UK’s ice shelves disintegrated from climate warming. 🧵 www.nature.com/articles/s41... @bas.ac.uk
nature.com
Change in iceberg calving behavior preceded North Sea ice shelf disintegration during the last deglaciation - Nature Communications
Massive tabular icebergs broke off of the UK during the last ice age. The widespread break-up of the ice shelves which produced these giant icebergs can be traced to around 18,000 years ago, and likel...
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Jonathan Amos @jcdamos.bsky.social · 24/04/2025
Mickey's recent GRL paper on trends/extremes in big Antarctic bergs is here: doi.org/10.1029/2024... And you can read the Kirkham paper in Nature Comms here: doi.org/10.1038/s414... And yours truly with the lead story on New Scientist online here: newscientist.com/article/2477... 😎
New Scientist front page
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Jonathan Amos @jcdamos.bsky.social · 24/04/2025
This underscores thinking about Antarctica. Large calvings like A23a are not necessarily a sign of instability. “Rather, ice shelves disintegrate via death by a thousand cuts. We should be concerned when we stop seeing the large calving events,” Mickey MacKie tells me.
Iceberg A23a
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Jonathan Amos @jcdamos.bsky.social · 24/04/2025
In other words, there’s a “regime change” in which large bergs are replaced by countless small bergs as the North Sea's ice shelves shatter in response to rising temperatures.
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Jonathan Amos @jcdamos.bsky.social · 24/04/2025
Here's the thing: In the North Sea, the comb-like furrows cut by the big bergs are eventually over-written by squiggly troughs made by the narrow keels of much smaller ice blocks.
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Jonathan Amos @jcdamos.bsky.social · 24/04/2025
In Antarctica, megabergs calve from ice shelves. The recognition that tabular bergs once existed in the North Sea tells us the seaward margins of the retreating British and Irish Ice Sheet at the end of the last glacial maximum also had ice shelves.
British and Irish Ice Sheet 20k years ago - BRITICE Project
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Jonathan Amos @jcdamos.bsky.social · 24/04/2025
"We can estimate from the extent of the scours and what is known about ancient sea levels that these bergs were probably five to a few tens of kilometres wide and perhaps a couple of hundred metres thick." ie Think blocks of ice the size of Cambridge or Bristol 😲
Iceberg and scourmarks graphic - Kirkham et al
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