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A novel transport assimilation method for the Atlantic meridional overturning circulation at 26°N
Author(s) -
Hermanson Leon,
Dunstone Nick,
Haines Keith,
Robson Jon,
Smith Doug,
Sutton Rowan
Publication year - 2014
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.2321
Subject(s) - thermohaline circulation , climatology , salinity , anomaly (physics) , data assimilation , ocean current , temperature salinity diagrams , environmental science , hadcm3 , geology , circulation (fluid dynamics) , zonal and meridional , oceanography , climate change , general circulation model , meteorology , gcm transcription factors , physics , mechanics , condensed matter physics
One of the prerequisites for achieving skill in decadal climate prediction is to initialize and predict the circulation in the Atlantic Ocean successfully. The RAPID array measures the Atlantic Meridional Overturning Circulation (MOC) at 26°N. Here we develop a method to include these observations in the Met Office Decadal Prediction System (DePreSys). The proposed method uses covariances of overturning transport anomalies at 26°N with ocean temperature and salinity anomalies throughout the ocean to create the density structure necessary to reproduce the observed transport anomaly. Assimilating transport alone in this way effectively reproduces the observed transport anomalies at 26°N and is better than using basin‐wide temperature and salinity observations alone. However, when the transport observations are combined with in situ temperature and salinity observations in the analysis, the transport is not currently reproduced so well. The reasons for this are investigated using pseudo‐observations in a twin experiment framework. Sensitivity experiments show that the MOC on monthly time‐scales, at least in the HadCM3 model, is modulated by a mechanism where non‐local density anomalies appear to be more important for transport variability at 26°N than local density gradients.