11/ Their computer modelling projects other changes in AABW such as meltwater, salinity and temperature by 2050 – “essentially an intensification of the patterns of change observed since the 1990s”, the review says.

10/ 𝗔𝗔𝗕𝗪 𝗶𝘀 𝗳𝗿𝗲𝘀𝗵𝗲𝗻𝗶𝗻𝗴. Melting ice shelves make the waters fresher and more buoyant. Another study by some of the same authors simulated the future response of the ocean to meltwater input, projecting a slowdown of the Antarctic overturning by 40% by 2050.

▶️ aappartnership.org.au/antarctic-de...

9/ 𝗔𝗔𝗕𝗪 𝗶𝘀 𝘁𝗵𝗶𝗻𝗻𝗶𝗻𝗴: since the mid-80s, at rates greater than 50 metres per decade in the deep Antarctic basins, with more rapid thinning observed closer to the sources of AABW. Contraction of AABW may lead to increased exposure of Antarctic ice shelves to warm water and further melt.

7/ So any change in AABW properties has consequences for the strength of the deep overturning circulation – and climatic patterns. We know that rapid change is already underway in the abyssal ocean.

Sea ice edge 📸 Todor Iolovski/AAD

8/ 𝗔𝗔𝗕𝗪 𝗶𝘀 𝘄𝗮𝗿𝗺𝗶𝗻𝗴. Since the mid-80s, ocean heat content below 4,000m has increased at a rate of about 13 trillion watts – about equal to the global energy consumption rate by humans each year.

6/ From these regions, AABW moves into the Pacific, Indian and Atlantic Oceans, driving many of the world's significant currents. This shows the fraction of water on the seafloor that is composed of AABW (dark blue is more than 90%, depths shallower than 3,500m not shown).

5/ AABW only forms in four locations: Weddell Sea, Cape Darnley, Ross Sea and Adelie Land. ‘Sv’ is a Sverdrup, a measure of current flow rate (1 Sv = 1 million cubic metres per second). Any changes in these regions (like sea ice) may impact the 3-D structure of the global overturning circulation.

4/ To form AABW, cascades of dense water spill from the continental shelf and sink to the deep ocean: seawater freezes to form sea ice ➡️ rejects brine ➡️ dense cold salty oxygen-rich water sinks ➡️ pumps oxygen into the deep sea ➡️ ‘ventilates’ abyss

Watch ▶️ vimeo.com/830053753

3/ How will this lifeline change on a warming planet? A new review in @natrevearthenviron.nature.com led by Steve Rintoul at CSIRO/AAPP examines the importance of AABW to ocean carbon and heat storage and oxygen supply to the deep sea – and the impacts of global heating.

Review ▶️ rdcu.be/eTWCD

2/ Driving the pump is Antarctic Bottom Water (AABW), cold dense water that sinks from the continental shelf to the deep (dark purple) and fills 36% of the global ocean volume. The sinking of AABW is balanced by a return flow of lighter warmer water (yellow).

Pic: @antarcticsciaus.bsky.social

Adrift like Shackleton: Robot float survives #Antarctic ice. The Argo float disappeared under the ice and survived to send back the first-ever ocean transect beneath an East Antarctic ice shelf.

www.csiro.au/en/news/All/...

7/ Hats off to authors Steve Rintoul, Esmee van Wijk, Laura Herraiz-Borreguero and Madelaine Rosevear from CSIRO, AAPP, @utas.edu.au and @imas-utas.bsky.social – with support from @imos-aus.bsky.social – and the intrepid #Argo floats.
@euro-argo.eu
@soccomproject.bsky.social
@soosocean.bsky.social

6/ This work reveals the Shackleton ice shelf is, for now, not exposed to warm water capable of melting it from below. However the Denman Glacier is and therefore more vulnerable. Its ice volume holds a potential 1.5-metre contribution to global sea level rise.

5/ That’s where floats can help, bumping their heads on the underside of ice shelves, measuring melt where it happens. Deploying an array of floats around Antarctica's continental shelf would reduce the large uncertainties in estimating future sea level rise.

▶️ theconversation.com/what-our-mis...

4/ But measuring inside ice shelf cavities is very difficult to do. Ice shelves can be hundreds of metres thick. While you can drill a hole through and lower your sensors, this is expensive and rarely done, so very few observations have been made.

▶️ aapp.shorthandstories.com/how-to-drill...

3/ Ice shelves resist the flow of continental ice to the sea. If warm ocean waters weaken the ice shelves, more ice will reach the ocean and melt, causing sea level to rise. Ocean measurements are critical to determine how much and how fast.

▶️ aapp.shorthandstories.com/opening-the-...

2/ After eight months hidden away, profiling the ocean from the seafloor to the base of the ice every five days, the Argo float survived to deliver the first-ever oceanographic transect from beneath an East Antarctic ice shelf.

▶️ aappartnership.org.au/adrift-like-...