data

20 mars 2024

New Sea Surface Salinity Record Released

Version 4.41 provides a global record and improves high-latitude observations (2010-2022)

Salinity, or saltiness, at the sea surface is an important driving force behind the conveyor-belt-like ocean circulation patterns that transport heat and carbon around the globe. Tracking this variable is critical for assessing the state of the ocean and also for understanding and forecasting climate phenomena such as the Pacific’s El Niño Southern Oscillation (ENSO) which can disrupt ecosystems, economies and human health.

The latest sea surface salinity derived from space has been recently released by researchers contributing to ESA Climate Change Initiative (CCI).

This new product, now in its fourth iteration (version 4.41) covers the period 2010-2022 and integrates measurements from L-band Microwave Imaging Radiometers from ESA’s Soil Moisture and Ocean Salinity (SMOS), and NASA Aquarius and Soil Moisture Active Passive (SMAP) satellite missions into one globally consistent record.

Extended by a further two years the record is available as a weekly and monthly product at ~50km spatial resolution and describes annual and interannual variability at large meso- to basin scales with unprecedented accuracy.

'Enhancements include seasonal bias corrections, stability at high latitudes and significantly improved sea surface salinity coverage in the polar regions,’ explains CCI Salinity project science leader, Jaqueline Boutin of Laboratoire d'Océanographie et du Climat (LOCEAN), France.

In line with a suite of almost 30 other projects comprising ESA’s Climate Change Initiative, this project is dedicated to generating robust, long-term satellite data records for climate applications and takes the Global Climate Observing System (GCOS) as reference. All data are fully-validated and uncertainty characterised into a consistent long-term record and so meets the key requirements that climate scientists consider when selecting which data to integrate into models used to predict future change.

Salinity: improving model outputs

Previous studies have demonstrated that assimilating sea surface salinity data into ocean/atmosphere models improves the representation of the oceans coupled dynamics. Importantly, when combined with observations of other climate variables such as sea surface temperature, the ability to forecast El Niño events improves. For example, model forecasts that use salinity information are useful for seven months, whereas this falls to four months when it is omitted.

El Niño events are associated with a periodic reduction, or switch, in easterly trade winds flow from the Americas to southeast Asia on normal years. This triggers changes in water and ocean surface heat movement and dramatic shifts in weather patterns around the world and a heightened risk of flood and drought extremes.

El nino and monitoring the ocean surface from space

The animation below illustrates how satellite observations of sea surface salinity and sea surface temperature can be used to track the evolution of el Nino events across the Pacific.