Local Air‐Sea Interactions at Ocean Mesoscale and Submesoscale in a Western Boundary Current

Abstract

We present results from a new, global, high‐resolution (∼3‐km for ocean and ∼6‐km for atmosphere) realistic earth system simulation. This simulation allows us to examine aspects of small‐scale air‐sea interaction beyond what previous studies have reported. Our study focuses on recurring intermittent wind events in the Gulf Stream region. These events induce local air‐sea heat fluxes above Sea Surface Temperature (SST) anomalies with horizontal scales smaller than 500‐km. In particular, strong latent heat bursts above warm SST anomalies are observed during these wind events. We show that such wind events are associated with a secondary circulation that acts to fuel the latent heat bursts by transferring dry air and momentum down to the surface. The intensity of this secondary circulation is related to the strength of small‐scale SST fronts that border SST anomalies. The study of such phenomena requires high‐resolution in both the atmospheric and oceanic components of the model.

Annual variations in phytoplankton biomass driven by small-scale physical processes

“…For instance, predator-prey interactions 68 , resource competition 69 , and the interplay between the two 46 , can lead to oscillations in phytoplankton biomass on short timescales (<3 months). On the other hand, airsea heat fluxes could damp the variability for SST; for example, through the air-sea turbulent heat flux feedback over mesoscale eddies, which has been recently identified in high resolution coupled ocean-atmosphere models 70,71 and quantified 72 . This effect could contribute to part of the differences observed in both the sub-seasonal and delta-seasonal components.…”

Scalings for Eddy Buoyancy Fluxes Across Prograde Shelf/Slope Fronts

“…Recent modeling studies estimated a horizontal grid spacing of 1/72 ° as the minimum requirement to resolve most (∼70%) of mesoscale processes over continental shelves and slopes globally (Holt et al., 2017). Such a fine resolution contrasts with the fact that even state‐of‐the‐art coupled global simulations are employing an ocean component with a grid spacing of ∼1/24° (e.g., the GEOS‐MITgcm simulation, Strobach et al., 2022) and that most IPCC‐class Earth System Models still adopt a horizontal resolution of 1° or coarser for the ocean component to accommodate lengthy integration and large ensembles.…”

On the Feedback Between Air‐Sea Turbulent Momentum Flux and Oceanic Submesoscale Processes

“…Neglecting the ocean surface currents in the wind stress calculation is one reason that has been put forward for the biases in air‐sea fluxes of heat and momentum in numerical models (Chelton et al., 2004; Dawe & Thompson, 2006; Duhaut & Straub, 2006; Scott & Arbic, 2007; Seo, 2017; Seo et al., 2016; Renault, Molemaker, Gula, et al., 2016; Renault, Molemaker, McWilliams, et al., 2016; Renault, McWilliams, & Masson, 2017; Renault, McWilliams, & Penven, 2017; Renault et al., 2018, 2020; Seo et al., 2019; Wu et al., 2017; Zhai & Greatbatch, 2007). Resolving the influence of sea surface temperature (SST) (on wind speed and boundary‐layer stratification) is also considered crucial in accurately modeling the air‐sea fluxes (Chelton et al., 2004; Gaube et al., 2015; Hayers et al., 1989; O’Neill et al., 2010; Seo, 2017; Seo et al., 2016; Shi & Bourassa, 2019; Small et al., 2008; Spall, 2007; Strobach et al., 2022; Sullivan et al., 2020). Furthermore, with more finer‐scale processes being resolved in ocean models due to the improvements in numerical techniques and computational resources, the biases of wind stress and heat flux at the air‐sea interface are found to be dependent on model resolutions (Renault et al., 2018, 2020).…”