# Argo data show Antarctic Intermediate Water saltier and denser since 2016 as sea-ice meltwater input falls

- Published: 2026-11-12 03:46 UTC
- Section: Planet › Ocean & water
- Tags: Antarctic Intermediate Water, AAIW salinity, Antarctic sea ice loss, sea-ice meltwater, Argo floats, overturning circulation, Southern Ocean, pycnocline, Nature Climate Change
- URL: https://realtech.media/news/rt-4c50e0ee44c1fd044487455c_argo_data_show/

**After record sea-ice losses from 2016, meltwater input to the Southern Ocean fell by nearly 36 mSv per decade, and the intermediate water layer began to salinify and densify.**

![Argo data show Antarctic Intermediate Water saltier and denser since 2016 as sea-ice meltwater input falls](https://realtech.media/media/2026/11/5b80061b811a9d7d.png)
*nature.com*

A research team led by Bishakhdatta Gayen (University of Melbourne and the Indian Institute of Science) and Kaushik Mishra (IISc) reports that Antarctic Intermediate Water (AAIW) has become saltier and denser since 2016. The study, published in Nature Climate Change and available on nature.com, used ocean observations from the Argo programme, supplemented by satellite and re-analysis datasets [1]. Argo is a network of about 4,000 robotic floats that sample the upper ocean.

## Sea ice and the intermediate water layer

AAIW is a key component of the global overturning circulation and a major regulator of pycnocline structure. It forms in the polar Southern Ocean, where sea-ice processes shape its properties [1]. Sustained sea-ice expansion over several decades up to 2015 enhanced summertime meltwater input, stratified the upper polar ocean and freshened AAIW [1].

Since 2016, repeated record sea-ice losses have reversed these trends, the authors report [1]. They estimate a net decline in sea-ice meltwater input of nearly 36 mSv per decade, compared with a pre-2016 increase of 14 mSv per decade [1]. Gayen said that until 2016 the seasonal summer melt was about triple the Amazon's annual flow of roughly 6,600 cubic km, and that after 2016 it dropped to roughly double.

## Measured changes in salinity and density

The sea-ice loss has triggered densification and salinification of AAIW. The core of the layer has salinified at 4.8 × 10−3 ± 1.7 × 10−3 g kg−1 per decade [1]. According to the study's summary, summer ice melt helped maintain the layer in 1995–2015, while in 2016–2024 the reduced freshwater input left it saltier, denser and deeper.

The analysis combines Argo-derived products (RG-ARGO, IAP and EN4.2.2) with satellite records of sea-ice concentration, drift and thickness, and with the GLORYS and SOSE ice–ocean re-analyses [1]. The authors state that these changes signal an ongoing hemispheric-scale reconfiguration of the pycnocline [1].

Co-author Alberto Naveira Garabato of the University of Southampton said that the altered water mass travels north across the Atlantic, Indian and Pacific oceans, and that this layer forms part of the upper limb of the global overturning circulation.

## Sources

1. [nature.com](https://www.nature.com/articles/s41558-026-02758-y)
2. [SciTechDaily](https://scitechdaily.com/antarcticas-melting-ice-has-triggered-a-sudden-shift-deep-in-the-ocean)

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Source: RealTech, realtech.media — https://realtech.media/news/rt-4c50e0ee44c1fd044487455c_argo_data_show/