Where to Look for Anthropogenic Climate Change in the Ocean

Helene Banks Hadley Centre for Climate Prediction and Research, Met Office, Bracknell, Berkshire, United Kingdom

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Richard Wood Hadley Centre for Climate Prediction and Research, Met Office, Bracknell, Berkshire, United Kingdom

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Abstract

A coupled climate model has been used to provide preliminary guidance on which ocean observations will be most useful for early detection of anthropogenic climate change. Given the sparsity of historical ocean measurements, early detection may need to be based on the differences between two snapshots of the ocean. This is the basis for this analysis. Sea surface temperature is shown to give a particularly good signal-to-noise ratio, justifying the use of surface temperature in almost all detection studies to date. Meridional heat transports are unlikely to be useful for detection of anthropogenic change, while measurements of the thermohaline circulation may require continuous time series. Previously subsurface temperature has been used in a integrated way to detect change. It is shown that subsurface temperature and salinity have the potential for detecting anthropogenic change on both pressure and density surfaces over 30 years. These results highlight the potential high signal-to-noise ratio in particular areas of the ocean: the Arctic and Atlantic, the North Pacific, and the Southern Ocean. Given that there already are historical measurements of the subsurface ocean temperature and salinity, this suggests that, in terms of detection of change in the ocean, monitoring of these should probably be one of the highest priorities and there should be an attempt to monitor regions (such as the Southern Ocean) that are historically data sparse. The results of this work will be of interest to observationalists and policy makers looking for an objective assessment of where to measure the ocean.

Corresponding author address: Helene T. Banks, Hadley Centre for Climate Prediction and Research, Met Office, London Road, Bracknell, Berkshire RG12 2SY, United Kingdom. Email: helene.banks@metoffice.com

Abstract

A coupled climate model has been used to provide preliminary guidance on which ocean observations will be most useful for early detection of anthropogenic climate change. Given the sparsity of historical ocean measurements, early detection may need to be based on the differences between two snapshots of the ocean. This is the basis for this analysis. Sea surface temperature is shown to give a particularly good signal-to-noise ratio, justifying the use of surface temperature in almost all detection studies to date. Meridional heat transports are unlikely to be useful for detection of anthropogenic change, while measurements of the thermohaline circulation may require continuous time series. Previously subsurface temperature has been used in a integrated way to detect change. It is shown that subsurface temperature and salinity have the potential for detecting anthropogenic change on both pressure and density surfaces over 30 years. These results highlight the potential high signal-to-noise ratio in particular areas of the ocean: the Arctic and Atlantic, the North Pacific, and the Southern Ocean. Given that there already are historical measurements of the subsurface ocean temperature and salinity, this suggests that, in terms of detection of change in the ocean, monitoring of these should probably be one of the highest priorities and there should be an attempt to monitor regions (such as the Southern Ocean) that are historically data sparse. The results of this work will be of interest to observationalists and policy makers looking for an objective assessment of where to measure the ocean.

Corresponding author address: Helene T. Banks, Hadley Centre for Climate Prediction and Research, Met Office, London Road, Bracknell, Berkshire RG12 2SY, United Kingdom. Email: helene.banks@metoffice.com

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