Overview
- A peer-reviewed study published in October 2026 reports that Antarctic Intermediate Water (AAIW) reversed decades of freshening and became measurably saltier and denser beginning around 2015.
- The authors calculate a mean salinity rise of about 0.0048 grams per kilogram per decade with larger changes in some regions and confirm the result using roughly 4,000 Argo floats, satellite sea-ice records and other ocean datasets.
- The team links the change to a sharp decline in Antarctic sea ice that reduced summer meltwater input and to increased upwelling of warmer, saltier deep water into the AAIW formation zone.
- Scientists warn that a saltier, denser AAIW can weaken ocean stratification, make it easier for stored deep-ocean carbon and heat to return toward the surface, and may alter regional sea levels and weather patterns if the change persists.
- Authors and other Antarctic researchers call for sustained observations and improved ocean modelling to track how this abrupt shift will propagate into global circulation and affect coastal communities and climate over coming decades.