UK Global Ocean GO6 and GO7: a traceable hierarchy of model resolutions

Storkey, David; Blaker, Adam T.; Mathiot, Pierre; Megann, Alex; Aksenov, Yevgeny; Blockley, Ed; Calvert, Daley; Graham, Tim; Hewitt, Helene T.; Hyder, Patrick; Kuhlbrodt, Till; Rae, Jamie; Sinha, Bablu

doi:10.5194/gmd-11-3187-2018

Cited by 169 publications

(236 citation statements)

References 74 publications

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“…Previous studies (e.g., Hewitt et al, ; Storkey et al, ) point out that increasing ocean resolution leads to increased AMOC. Interestingly, we do not see this in our simulations.…”

Section: Discussionmentioning

confidence: 95%

The Relative Influence of Atmospheric and Oceanic Model Resolution on the Circulation of the North Atlantic Ocean in a Coupled Climate Model

Sein

Koldunov

Danilov

et al. 2018

J Adv Model Earth Syst

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It is often unclear how to optimally choose horizontal resolution for the oceanic and atmospheric components of coupled climate models, which has implications for their ability to make best use of available computational resources. Here we investigate the effect of using different combinations of horizontal resolutions in atmosphere and ocean on the simulated climate in a global coupled climate model (Alfred Wegener Institute Climate Model [AWI‐CM]). Particular attention is given to the Atlantic Meridional Overturning Circulation (AMOC). Four experiments with different combinations of relatively high and low resolutions in the ocean and atmosphere are conducted. We show that increases in atmospheric and oceanic resolution have clear impacts on the simulated AMOC, which are largely independent. Increased atmospheric resolution leads to a weaker AMOC. It also improves the simulated Gulf Stream separation; however, this is only the case if the ocean is locally eddy resolving and reacts to the improved atmosphere. We argue that our results can be explained by reduced mean winds caused by higher cyclone activity. Increased resolution of the ocean affects the AMOC in several ways, thereby locally increasing or reducing the AMOC. The finer topography (and reduced dissipation) in the vicinity of the Caribbean basin tends to locally increase the AMOC. However, there is a reduction in the AMOC around 45°N, which relates to the reduced mixed layer depth in the Labrador Sea in simulations with refined ocean and changes in the North Atlantic current pathway. Furthermore, the eddy‐induced changes in the Southern Ocean increase the strength of the deep cell.

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“…Previous studies (e.g., Hewitt et al, ; Storkey et al, ) point out that increasing ocean resolution leads to increased AMOC. Interestingly, we do not see this in our simulations.…”

Section: Discussionmentioning

confidence: 95%

The Relative Influence of Atmospheric and Oceanic Model Resolution on the Circulation of the North Atlantic Ocean in a Coupled Climate Model

Sein

Koldunov

Danilov

et al. 2018

J Adv Model Earth Syst

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“…The pattern in N216ORCA025 (Figure d) is very similar, notably the strong salty bias in the Bay of Bengal and the fresh biases in the subtropical Pacific on both hemispheres. To some degree, these regional biases also appear in ocean‐only, forced simulations (Storkey et al, ), indicating that they occur independent of coupled feedbacks.…”

Section: Evaluation and Scientific Performancementioning

confidence: 91%

The Low‐Resolution Version of HadGEM3 GC3.1: Development and Evaluation for Global Climate

Kuhlbrodt

Jones

Sellar

et al. 2018

J Adv Model Earth Syst

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185

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A new climate model, HadGEM3 N96ORCA1, is presented that is part of the GC3.1 configuration of HadGEM3. N96ORCA1 has a horizontal resolution of ~135 km in the atmosphere and 1° in the ocean and requires an order of magnitude less computing power than its medium‐resolution counterpart, N216ORCA025, while retaining a high degree of performance traceability. Scientific performance is compared to both observations and the N216ORCA025 model. N96ORCA1 reproduces observed climate mean and variability almost as well as N216ORCA025. Patterns of biases are similar across the two models. In the northwest Atlantic, N96ORCA1 shows a cold surface bias of up to 6 K, typical of ocean models of this resolution. The strength of the Atlantic meridional overturning circulation (16 to 17 Sv) matches observations. In the Southern Ocean, a warm surface bias (up to 2 K) is smaller than in N216ORCA025 and linked to improved ocean circulation. Model El Niño/Southern Oscillation and Atlantic Multidecadal Variability are close to observations. Both the cold bias in the Northern Hemisphere (N96ORCA1) and the warm bias in the Southern Hemisphere (N216ORCA025) develop in the first few decades of the simulations. As in many comparable climate models, simulated interhemispheric gradients of top‐of‐atmosphere radiation are larger than observations suggest, with contributions from both hemispheres. HadGEM3 GC3.1 N96ORCA1 constitutes the physical core of the UK Earth System Model (UKESM1) and will be used extensively in the Coupled Model Intercomparison Project 6 (CMIP6), both as part of the UK Earth System Model and as a stand‐alone coupled climate model.

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“…The ORCA12 grid thus provides a resolution of 9 km at the equator and 2 km in the Canadian Archipelago. The ocean comprises 75 unevenly spaced vertical levels varying from about 1 m thick at the surface to around 200 m thick at 5000 m. Further details of the ocean model can be found in Storkey et al (). The model is computationally very expensive, which limits the length of simulations.…”

Section: Models and Methodsmentioning

confidence: 99%

Interconnectivity Between Volume Transports Through Arctic Straits

et al. 2018

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Arctic heat and freshwater budgets are highly sensitive to volume transports through the Arctic‐Subarctic straits. Here we study the interconnectivity of volume transports through Arctic straits in three models; two coupled global climate models, one with a third‐degree horizontal ocean resolution (High Resolution Global Environmental Model version 1.1 [HiGEM1.1]) and one with a twelfth‐degree horizontal ocean resolution (Hadley Centre Global Environment Model 3 [HadGEM3]), and one ocean‐only model with an idealized polar basin (tenth‐degree horizontal resolution). The two global climate models indicate that there is a strong anticorrelation between the Bering Strait throughflow and the transport through the Nordic Seas, a second strong anticorrelation between the transport through the Canadian Arctic Archipelago and the Nordic Seas transport, and a third strong anticorrelation is found between the Fram Strait and the Barents Sea throughflows. We find that part of the strait correlations is due to the strait transports being coincidentally driven by large‐scale atmospheric forcing patterns. However, there is also a role for fast wave adjustments of some straits flows to perturbations in other straits since atmospheric forcing of individual strait flows alone cannot lead to near mass balance fortuitously every year. Idealized experiments with an ocean model (Nucleus for European Modelling of the Ocean version 3.6) that investigate such causal strait relations suggest that perturbations in the Bering Strait are compensated preferentially in the Fram Strait due to the narrowness of the western Arctic shelf and the deeper depth of the Fram Strait.

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UK Global Ocean GO6 and GO7: a traceable hierarchy of model resolutions

Cited by 169 publications

References 74 publications

The Relative Influence of Atmospheric and Oceanic Model Resolution on the Circulation of the North Atlantic Ocean in a Coupled Climate Model

The Relative Influence of Atmospheric and Oceanic Model Resolution on the Circulation of the North Atlantic Ocean in a Coupled Climate Model

The Low‐Resolution Version of HadGEM3 GC3.1: Development and Evaluation for Global Climate

Interconnectivity Between Volume Transports Through Arctic Straits

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