Marine Boundary Layer Processes Constrained by Multi-Year Concomitant In-Situ Water Vapor and Precipitation Isotope Measurements from Land-Based and Ship-Based Monitoring Sites in the North Atlantic

Abstract:

In the global hydrological cycle the marine boundary layer plays a key role. Understanding and constraining the processes governing the water vapor isotopic composition is therefore crucial in order to improve future projection of climate change.

We present here concomitant in-situ water vapor and precipitation isotope measurements carried out for several years at monitoring stations across the North Atlantic. Our observations have been carried out in different climate regions, which allow us to characterize the influence of sea surface temperature, and across several years, which allow us to separate the seasonal influence. Using this extensive dataset we focus specifically on the parameterization of the kinetic effects during evaporation from the ocean surface. We address the observed apparent lack of wind speed and sea surface temperature effect on the marine boundary layer water vapor isotopic composition by comparing the formulation by Merlivat and Jouzel (1979) and the formulation by Craig and Gordon (1964) against our water vapor and precipitation isotope observations and using calculations of backwards trajectories.