2021 State of the Environment Report Marine Chapter – Expert Assessment – Pressure – Climate Change – Sea surface temperature and salinity

The Marine chapter of the 2021 State of the Environment (SoE) report incorporates multiple expert templates developed from streams of marine data. This metadata record describes the Expert Assessment "Pressures on the marine environment - climate change - Sea surface temperature and salinity ". 
<strong><em>A PDF of the full Expert Assessment, including figures and tables (where provided) is downloadable in the "On-line Resources" section of this record as "EXPERT ASSESSMENT 2021 - Sea surface temperature and salinity "</em></strong>



DESCRIPTION OF PRESSURE
Ocean temperature and salinity are fundamental water properties that shape Australia’s marine environment, from the coast to the continental shelf edge and open ocean. Climate change driven trends in sea surface temperature and salinity are changes in these water properties owing to anthropogenic influences. Long-term trends in sea surface temperatures are controlled by changes in the atmospheric circulation and air-sea heat fluxes, ocean heat transport, and the mixed layer depth. Long-term trends in sea surface salinity are caused by changes in evaporation and precipitation at the air-sea interface, ocean salt transport, river runoff, and melting and freezing of glacial and sea ice.  

DATA STREAM(S) USED IN EXPERT ASSESSMENT
Data sets had either global coverage, including Australia, or at Australian specific sites. Some data products included in situ data sources dating back to the 1950s or earlier (e.g. WOD and ERSSTv5), while others (OISST v2.1) incorporate satellite remote sensing with other data products since the 1980s. The Argo program started in 2000 and samples the open ocean globally, with nearly 4000 active floats in 2021. 



2021 SOE ASSESSMENT SUMMARY [see attached Expert Assessment for full details]

• 2021 •
--Assessment grade:-- Very high impact:  Climate change influence on sea surface temperature and salinity affects Australian marine environment with high-impact, enduring changes to marine ecosystems documented in past five years. 
--Assessment trend:-- Deteriorating:  Climate change influence on sea surface temperature and salinity evident from recent studies and with projections indicating continued increasing pressure on ecosystems. 
--Confidence grade:-- Adequate: High-quality evidence and high level of consensus.  Observations and models indicate climate change influence on sea surface temperature and salinity trends, with sparse and reduced data availability prior to the 1950s. 
--Confidence trend:-- Adequate: High-quality evidence and high level of consensus.   Separating climate change influence on trends from other sources of variability can be conducted with sustained long-term monitoring, improved data collection by in situ and remote sensing, and integration with ocean models.
--Comparability:-- Somewhat comparable: Grade and trend are somewhat comparable to the previous assessment.  This assessment considers climate change influences on sea surface temperature and salinity, which was previously separated as two assessments.  



CHANGES SINCE 2016 SOE ASSESSMENT
This assessment differs from the 2016 assessment, which included two separate assessments on the pressures on the marine environment from “Climate change – sea surface temperature” (Assessment Grade: High Impact) and “Ocean salinity” (Assessment Grade: Low impact).
https://catalogue.aodn.org.au:443/geonetwork/srv/api/records/cca8c5ce-4b21-406d-b20c-7b333f8e605c
https://catalogue.aodn.org.au:443/geonetwork/srv/api/records/86ec16dd-99b7-400d-b054-d218da14858c
Overall, there is more data available, current time series products, and evidence for climate change influence on sea surface temperature than for sea surface salinity as a pressure on the Australian marine environment. The combined assessment for “Climate change – sea surface temperature and salinity” is weighted toward the climate change influence on sea surface temperature and in acknowledging their impacts on the Australian marine environment over the past five years. In addition, sea surface salinity trends are interconnected with sea surface temperature trends through physical feedbacks in the marine environment.

Tags: anthropogenic pressures, climate change, environmental pressures, expert assessment, ocean salinity, sea surface temperature (SST)
Organization: Australian Ocean Data Network