Shelf Processes Leave Antarctic Ocean Carbon Largely Unchanged
Polarstern expedition samples from 2016 and 2021 show dissolved organic matter stayed nearly constant as water sank into the deep ocean.
Updated on Nov. 10, 2026 in Environmental
A study published in Nature Communications analysed water samples from two Polarstern expeditions in 2016 and 2021 to examine carbon on the Antarctic continental shelf. The amount and composition of dissolved organic matter remained almost unchanged as dense water sank into the deep ocean.
Why it matters
The Antarctic continental shelf is an important site for the formation of Antarctic bottom water, so whether shelf processes alter carbon before it sinks affects how the ocean stores carbon. Dissolved organic matter is the largest reservoir of organic carbon in the ocean.
The study analysed samples from Polarstern expeditions in 2016 and 2021, and dense waters remain on the Weddell Sea shelf for six to twelve years before sinking. Researchers have not yet measured carbon movement during the Antarctic winter, which a planned 2028 expedition is designed to study.
The players
Alfred Wegener Institute (AWI)
The Alfred Wegener Institute is a German polar and marine research centre that operates the Polarstern icebreaker and the MICADAS radiocarbon facility used in this study.
Dr Gonzalo V. Gomez-Saez
Dr Gomez-Saez led the study and is now based at Ludwig-Maximilians-Universität München, where he continues research on marine carbon cycling.
The details
The team used several complementary analytical methods, including ICBM instruments that examined the molecular make-up and structure of organic matter mixtures, and AWI's MICADAS facility to determine the age of the carbon. Dense water circulates underneath the Filchner-Ronne Ice Shelf during its stay on the shelf.
Timeline
2016: First Polarstern expedition sampled water in the southern Weddell Sea.
2021: Second Polarstern expedition sampled water in the southern Weddell Sea.
2028: A planned Polarstern expedition to the Weddell Sea will study carbon movement during the Antarctic winter.
The Big Picture
The study builds on repeated Polarstern sampling of the southern Weddell Sea in 2016 and 2021 to test whether shelf waters modify carbon before it reaches the deep ocean. Its finding that the dissolved organic carbon reservoir may stay largely unaffected by climate change in this region narrows a key uncertainty for models of Antarctic bottom water formation.
The findings suggest the dissolved organic carbon stored in Antarctic bottom water may be relatively stable, which bears on how carbon storage in the deep ocean is projected to develop. The research remains at the level of ocean science and does not yet translate into changes to consumer products or policy.
The takeaway
Carbon carried by Antarctic shelf water appears to survive its trip to the deep ocean largely intact. That stability helps scientists better model how the ocean will store carbon in the coming decades.
What happens next
A Polarstern expedition to the Weddell Sea is planned for 2028 to study carbon movement during the Antarctic winter.
Further reading
For related background on how the ocean stores carbon, see Environmental coverage.
