A New Method Disentangles How the Atmosphere and Ocean Interact to Influence Climate
The oceans and the atmosphere are deeply connected and involved in a tangled network of two-way interactions. These connections influence how the Earth system responds to changes from external factors (like increasing CO2 concentrations), but their complexity makes it difficult to disentangle the individual roles of the atmosphere and ocean. The method introduced here helps separate their contributions and allows for more accurate interpretations of climate model simulations and projections of environmental change in the Earth system.
This method provides more accurate isolation of the oceans’ and atmosphere’s roles than previous approaches. Improved isolation of their roles will also facilitate a better understanding of how errors in the individual ocean and atmosphere model components contribute to the biases of coupled Earth system models. It also helps clarify how ocean-atmosphere interactions affect features of the Earth system, such as ocean overturning circulation in the Atlantic and sea ice loss, that are very important responses to increasing CO2.
Forced changes and natural (yearly and decadal) variations in climate fields (like air temperature, winds, ocean currents, and sea ice amount) are produced by processes occurring in the atmosphere and ocean and their interactions. This study describes a method that helps untangle these interactions, separate the components of climate variations caused by the atmospheric and oceanic changes, and explore how the interactions between them explain climate variability and change. Two climate model experiments applied the method of understanding the planet’s response to quadrupled CO2 concentrations. One experiment allowed all modeled interactions between the atmosphere and ocean to occur and the other (termed “partially coupled”) experiment excluded the role of ocean circulation changes in the interactions, isolating the climatic changes caused by the atmospheric CO2 increase alone. The difference between the two experiments revealed the climate changes attributable to ocean circulation changes. The researchers performed an additional, independent experiment to verify that the climate changes associated with the ocean circulation changes diagnosed from the partially coupled analysis were correct.