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Previous modeling and observational studies have established that it is possible to accurately monitor the Atlantic Meridional Overturning Circulation (AMOC) at 26.5°N using a coast-to-coast array of instrumented moorings supplemented by direct transport measurements in key boundary regions (the RAPID/MOCHA/WBTS Array). The main sources of observational and structural errors have been identified in a variety of individual studies. Here a unified framework for identifying and quantifying structural errors associated with the RAPID array-based AMOC estimates is established using a high-resolution (eddy resolving at low-mid latitudes, eddy permitting elsewhere) ocean general circulation model, which simulates the ocean state between 1978 and 2010. We define a virtual RAPID array in the model in close analogy to the real RAPID array and compare the AMOC estimate from the virtual array with the true model AMOC. The model analysis suggests that the RAPID method underestimates the mean AMOC by ∼1.5 Sv (1 Sv = 106 m3 s−1) at ∼900 m depth, however it captures the variability to high accuracy. We examine three major contributions to the streamfunction bias: (i) due to the assumption of a single fixed reference level for calculation of geostrophic transports, (ii) due to regions not sampled by the array and (iii) due to ageostrophic transport. A key element in (i) and (iii) is use of the model sea surface height to establish the true (or absolute) geostrophic transport. In the upper 2000 m, we find that the reference level bias is strongest and most variable in time, whereas the bias due to unsampled regions is largest below 3000 m. The ageostrophic transport is significant in the upper 1000 m but shows very little variability. The results establish, for the first time, the uncertainty of the AMOC estimate due to the combined structural errors in the measurement design and suggest ways in which the error could be reduced. Our work has applications to basin-wide circulation mea

Previous modeling and observational studies have established that it is possible to accurately monitor the Atlantic Meridional Overturning Circulation (AMOC) at 26.5°N using a coast-to-coast array of instrumented moorings supplemented by direct transport measurements in key boundary regions (the RAPID/MOCHA/WBTS Array). The main sources of observational and structural errors have been identified in a variety of individual studies. Here a unified framework for identifying and quantifying structural errors associated with the RAPID array-based AMOC estimates is established using a high-resolution (eddy resolving at low-mid latitudes, eddy permitting elsewhere) ocean general circulation model, which simulates the ocean state between 1978 and 2010. We define a virtual RAPID array in the model in close analogy to the real RAPID array and compare the AMOC estimate from the virtual array with the true model AMOC. The model analysis suggests that the RAPID method underestimates the mean AMOC by ∼1.5 Sv (1 Sv = 106 m3 s−1) at ∼900 m depth, however it captures the variability to high accuracy. We examine three major contributions to the streamfunction bias: (i) due to the assumption of a single fixed reference level for calculation of geostrophic transports, (ii) due to regions not sampled by the array and (iii) due to ageostrophic transport. A key element in (i) and (iii) is use of the model sea surface height to establish the true (or absolute) geostrophic transport. In the upper 2000 m, we find that the reference level bias is strongest and most variable in time, whereas the bias due to unsampled regions is largest below 3000 m. The ageostrophic transport is significant in the upper 1000 m but shows very little variability. The results establish, for the first time, the uncertainty of the AMOC estimate due to the combined structural errors in the measurement design and suggest ways in which the error could be reduced. Our work has applications to basin-wide circulation mea

The MarQUEST (Marine Biogeochemistry and Ecosystem Modelling Initiative in QUEST) project was established to develop improved descriptions of marine biogeochemistry, suited for the next generation of Earth system models. We review progress in these areas providing insight on the advances that have been made as well as identifying remaining key outstanding gaps for the development of the marine component of next generation Earth system models. The following issues are discussed and where appropriate results are presented; the choice of model structure, scaling processes from physiology to functional types, the ecosystem model sensitivity to changes in the physical environment, the role of the coastal ocean and new methods for the evaluation and comparison of ecosystem and biogeochemistry models. We make recommendations as to where future investment in marine ecosystem modelling should be focused, highlighting a generic software framework for model development, improved hydrodynamic models, and better parameterisation of new and existing models, reanalysis tools and ensemble simulations. The final challenge is to ensure that experimental/observational scientists are stakeholders in the models and vice versa.

The MarQUEST (Marine Biogeochemistry and Ecosystem Modelling Initiative in QUEST) project was established to develop improved descriptions of marine biogeochemistry, suited for the next generation of Earth system models. We review progress in these areas providing insight on the advances that have been made as well as identifying remaining key outstanding gaps for the development of the marine component of next generation Earth system models. The following issues are discussed and where appropriate results are presented; the choice of model structure, scaling processes from physiology to functional types, the ecosystem model sensitivity to changes in the physical environment, the role of the coastal ocean and new methods for the evaluation and comparison of ecosystem and biogeochemistry models. We make recommendations as to where future investment in marine ecosystem modelling should be focused, highlighting a generic software framework for model development, improved hydrodynamic models, and better parameterisation of new and existing models, reanalysis tools and ensemble simulations. The final challenge is to ensure that experimental/observational scientists are stakeholders in the models and vice versa.

The MarQUEST (Marine Biogeochemistry and Ecosystem Modelling Initiative in QUEST) project was established to develop improved descriptions of marine biogeochemistry, suited for the next generation of Earth system models. We review progress in these areas providing insight on the advances that have been made as well as identifying remaining key outstanding gaps for the development of the marine component of next generation Earth system models. The following issues are discussed and where appropriate results are presented; the choice of model structure, scaling processes from physiology to functional types, the ecosystem model sensitivity to changes in the physical environment, the role of the coastal ocean and new methods for the evaluation and comparison of ecosystem and biogeochemistry models. We make recommendations as to where future investment in marine ecosystem modelling should be focused, highlighting a generic software framework for model development, improved hydrodynamic models, and better parameterisation of new and existing models, reanalysis tools and ensemble simulations. The final challenge is to ensure that experimental/observational scientists are stakeholders in the models and vice versa

The physical context for ocean margin exchange at Goban Spur is described. Observations adjacent to, prior to and during the Ocean Margin EXchange (OMEX) project of 1993-1996 are used. They include currents measured on moorings, drogued-buoy tracks; temperature and other data from CTD profiles, especially as indicators of vertical mixing; evidence from models, particularly for turbulence causing vertical mixing. These data are combined in estimates of (seasonally dependent) mean flow, tidal currents, other current variability, exchange and mixing over the main cross-slope section studied in OMEX and in nearby and contrasted locations (aided by the use of earlier and adjacent measurements). Causative physical processes are discussed: potentially northward flow along the continental slope, effects of Goban Spur topography, eddies, wind-driven transport, cascading, tides, fronts, internal tides, internal waves, surface waves. Among these, there is evidence thatthe along-slope flow, typically O(0.05ms(-1)), is reduced or even reversed in spring, is generally weaker than at some other margin sectors owing to the non-meridional alignment and indentations in the Celtic Sea slope, and may sometimes overshoot rather than follow the depth contours around Goban Spur;tidal currents are O(0.2ms(-1)) on the adjacent shelf but O(0.1ms(-1)) or less over most of Goban Spur; they increase to the southeast;other (wind- and eddy-forced) contributions to the currents are typically O(0.1ms(-1)) or less, except on the shelf, and decrease with depth;wind-, tide- and wave-forced currents are probably the most consistent agents of cross-slope exchange O(1m(2)s(-1)), with topographic effects being important locally (canyons, spurs);stratification starts intermittently until early June, becomes shallower through June and deepens by September. In 1995, one storm on 5-8 September roughly doubled the upper mixed-layer depth to > 40m and reinstated maximal primary production in the upper mixed lay

The physical context for ocean margin exchange at Goban Spur is described. Observations adjacent to, prior to and during the Ocean Margin EXchange (OMEX) project of 1993-1996 are used. They include currents measured on moorings, drogued-buoy tracks; temperature and other data from CTD profiles, especially as indicators of vertical mixing; evidence from models, particularly for turbulence causing vertical mixing. These data are combined in estimates of (seasonally dependent) mean flow, tidal currents, other current variability, exchange and mixing over the main cross-slope section studied in OMEX and in nearby and contrasted locations (aided by the use of earlier and adjacent measurements). Causative physical processes are discussed: potentially northward flow along the continental slope, effects of Goban Spur topography, eddies, wind-driven transport, cascading, tides, fronts, internal tides, internal waves, surface waves. Among these, there is evidence thatthe along-slope flow, typically O(0.05ms(-1)), is reduced or even reversed in spring, is generally weaker than at some other margin sectors owing to the non-meridional alignment and indentations in the Celtic Sea slope, and may sometimes overshoot rather than follow the depth contours around Goban Spur;tidal currents are O(0.2ms(-1)) on the adjacent shelf but O(0.1ms(-1)) or less over most of Goban Spur; they increase to the southeast;other (wind- and eddy-forced) contributions to the currents are typically O(0.1ms(-1)) or less, except on the shelf, and decrease with depth;wind-, tide- and wave-forced currents are probably the most consistent agents of cross-slope exchange O(1m(2)s(-1)), with topographic effects being important locally (canyons, spurs);stratification starts intermittently until early June, becomes shallower through June and deepens by September. In 1995, one storm on 5-8 September roughly doubled the upper mixed-layer depth to > 40m and reinstated maximal primary production in the upper mixed lay

The physical context for ocean margin exchange at Goban Spur is described. Observations adjacent to, prior to and during the Ocean Margin EXchange (OMEX) project of 1993-1996 are used. They include currents measured on moorings, drogued-buoy tracks; temperature and other data from CTD profiles, especially as indicators of vertical mixing; evidence from models, particularly for turbulence causing vertical mixing. These data are combined in estimates of (seasonally dependent) mean flow, tidal currents, other current variability, exchange and mixing over the main cross-slope section studied in OMEX and in nearby and contrasted locations (aided by the use of earlier and adjacent measurements). Causative physical processes are discussed: potentially northward flow along the continental slope, effects of Goban Spur topography, eddies, wind-driven transport, cascading, tides, fronts, internal tides, internal waves, surface waves. Among these, there is evidence thatthe along-slope flow, typically O(0.05ms(-1)), is reduced or even reversed in spring, is generally weaker than at some other margin sectors owing to the non-meridional alignment and indentations in the Celtic Sea slope, and may sometimes overshoot rather than follow the depth contours around Goban Spur;tidal currents are O(0.2ms(-1)) on the adjacent shelf but O(0.1ms(-1)) or less over most of Goban Spur; they increase to the southeast;other (wind- and eddy-forced) contributions to the currents are typically O(0.1ms(-1)) or less, except on the shelf, and decrease with depth;wind-, tide- and wave-forced currents are probably the most consistent agents of cross-slope exchange O(1m(2)s(-1)), with topographic effects being important locally (canyons, spurs);stratification starts intermittently until early June, becomes shallower through June and deepens by September. In 1995, one storm on 5-8 September roughly doubled the upper mixed-layer depth to > 40m and reinstated maximal primary production in the upper mixed lay