To undertake a review of the observing system capacity for capturing changes in heat and freshwater storage and transports.
Observations of temperature and salinity are the foundations of the sustained observing system. The observational requirements and the observing capabilities to measure temperature and salinity have evolved significantly since the 1999 Upper Ocean Thermal Review and the global plans for a sustained ocean observing system for climate outlined in the OceanObs’99 conference.
Considerable advances in the global ocean observing system over the last two decades offer an opportunity to provide more quantitative information on changes in heat and freshwater storage. Variations in these storage terms can arise through internal variability and the response of the ocean to anthropogenic climate change. Disentangling these competing influences on the regional patterns of change and elucidating their governing processes remains an outstanding scientific challenge. This challenge is compounded by instrumental and sampling uncertainties. The combined use of ocean observations and model simulations is the most viable method to assess the forced signal from noise and ascertain the primary drivers of variability and change. Moreover, this approach offers the potential for improved seasonal-to-decadal predictions and the possibility to develop powerful multi-variate constraints on climate model projections. Regional heat storage changes dominate the steric contribution to sea level rise over most of the ocean and are vital to understanding both global and regional heat budgets. Variations in regional freshwater storage are particularly relevant to our understanding of changes in the hydrological cycle and can potentially be used to verify local ocean mass addition from terrestrial and cryosphere systems associated with contemporary sea level rise.
This OOPC review will:
- Explore the use of observation-based estimates of large-scale ocean heat and freshwater transport and storage in model evaluation, assessment and development.
- Assess the current capability of the ocean observing system to measure ocean heat and freshwater transport and storage changes, including budget constraints at global and regional scales to identify priority areas for new observations.
- Assess CMIP6 models fitness-for-purpose in diagnosing forced heat and freshwater changes, including global and regional conservation of ocean heat and freshwater, systematic model biases, and model representation of regional heat/freshwater budgets.
Recommendations on observing system gaps and adjustments to optimize the system, improved integration across observing platforms and regional networks.
Heat and Freshwater Storage and Transports in Observations and Climate Models, Oct / Nov 2021.