The atmosphere and ocean constantly interact by exchanging heat, moisture, and momentum in the form of wind and currents. This air-sea flux has a major impact on global climate, and ocean models that accurately capture it are important for improving weather forecasts and predictions of future climate conditions.
In a recent study, Roberts et al. investigated two ocean models with different levels of resolution to determine how well they capture small-scale air-sea flux and large-scale heat transport. They found that a lower-resolution model is sufficient for capturing air-sea flux in some cases, but a higher-resolution model more accurately simulates large-scale heat transport in the North Atlantic.
The lower-resolution model is known as an “eddy-permitting” model because it can roughly capture ocean storms, which it does at a resolution of 0.25° latitude and longitude. The higher-resolution “eddy-resolving” model captures ocean storms more realistically, at a resolution of 1/12 of a degree.
The researchers paired each ocean model with an atmospheric model to simulate air-sea flux across the globe over the course of 20 years. When they compared the model results with observational data for the same time frame, they found that the eddy-permitting model was nearly as effective as the eddy-resolving model in capturing air-sea flux interactions.
Most previous studies have compared eddy-resolving models of 0.1° resolution with 1° resolution models (more typically used for long climate simulations), finding the lower resolution to be inadequate. The new findings show that a 0.25° resolution eddy-permitting model may be sufficient and more affordable for some researchers who might otherwise have considered an eddy-resolving model.
However, the team found that the eddy-resolving model did a much better job of capturing average sea surface temperatures and therefore heat exchange with the atmosphere in the North Atlantic. The resulting simulation of ocean heat transport in the region more closely matched actual observations.
If supported by further research, these findings could help researchers refine climate models and improve future climate projections. (Geophysical Research Letters, doi:10.1002/2016GL070559, 2016)
—Sarah Stanley, Freelance Writer