Differences in Eastern North Pacific Stratification and Their Potential Impact on the Depth of Winter Mixing in CMIP5 Models

Abstract

AbstractUpper ocean stratification is known to play an important role in the seasonal evolution of the ocean mixed layer depth. This study examines biases in climatological upper ocean stratification in the Coupled Model Intercomparison Project version 5 historical simulations in the North Pacific. To quantify the potential impact of these stratification differences on the depth of winter mixing in two regions (the eastern subarctic and subtropical gyres), regionally averaged August stratification profiles were advanced to March using common atmospheric forcing fields and a single‐column mixed layer model. This approach is supported by correlation between the climate models' March mixed layer depth fields and those predicted by the one‐dimensional model. Substantial observation/model and model/model differences in predicted winter mixed layer depth have broad implications for how the climate models regulate the ocean‐atmosphere interactions that set thermocline water properties and impact nutrient supply to the upper ocean.