Wind work at the air-sea interface: a modeling study in anticipation of future space missions

Abstract

Abstract. Wind work at the air-sea interface is the transfer of kinetic energy between the ocean and the atmosphere and, as such, is an important part of the ocean-atmosphere coupled system. Wind work is defined as the scalar product of ocean wind stress and surface current, with each of these two variables spanning, in this study, a broad range of spatial and temporal scales, from 10 km to more than 3000 km and hours to months. These characteristics emphasize wind work's multiscale nature. In the absence of appropriate global observations, our study makes use of a new global, coupled ocean-atmosphere simulation, with horizontal grid spacing of 2–5 km for the ocean and 7 km for the atmosphere, analyzed for 12 months. We develop a methodology, both in physical and spectral spaces, to diagnose three different components of wind work that force distinct classes of ocean motions, including high-frequency internal gravity waves, such as near-inertial oscillations, low-frequency currents such as those associated with eddies, and seasonally averaged currents, such as zonal tropical and equatorial jets. The total wind work, integrated globally, has a magnitude close to 5 TW, a value that matches recent estimates. Each of the first two components that force high-frequency and low-frequency currents, accounts for ∼ 28 % of the total wind work and the third one that forces seasonally averaged currents, ∼ 44 %. These three components, when integrated globally, weakly vary with seasons but their spatial distribution over the oceans has strong seasonal and latitudinal variations. In addition, the high-frequency component that forces internal gravity waves, is highly sensitive to the collocation in space and time (at scales of a few hours) of wind stresses and ocean currents. Furthermore, the low-frequency wind work component acts to dampen currents with a size smaller than 250 km and strengthen currents with larger sizes. This emphasizes the need to perform a full kinetic budget involving the wind work and nonlinear advection terms as small and larger-scale low-frequency currents interact through these nonlinear terms. The complex interplay of surface wind stresses and currents revealed by the numerical simulation motivates the need for winds and currents satellite missions to directly observe wind work.

Sub‐Mesoscale Wind‐Front Interactions: The Combined Impact of Thermal and Current Feedback

“…The simulation was initialized on 20 January 2012, and results shown below are based on output from June 1st to 31 August 2012 (JJA). This configuration is identical to that used in Torres et al (2022), from which the readers can find more general information on the model and experiment setup. The unprecedented spatial and temporal resolutions of this global coupled simulation make it a unique and necessary tool to study meso-to-submesoscale wind-front interactions, a regime that remains under-explored.…”

Closing the loops on Southern Ocean dynamics: From the circumpolar current to ice shelves and from bottom mixing to surface waves

“…However, more recent studies have highlighted the important role of the synoptically varying winds (here, this refers to winds varying on "short" timescales of hours to days), which can result in a 70% increase in power input into the ocean from the winds (Zhai et al, 2012). Most of this energy enters the ocean in the winter time and in regions with strong synoptic wind variability, such as the Southern Ocean (Torres et al, 2022). The wind stress injects energy into both geostrophic and higher frequency motions (especially near the inertial frequency) and from the latter, near-inertial waves are energised that propagate down below the mixed layer into the deep ocean ( § 5.3).…”

Resonant Diurnal Internal Tides in the North Atlantic: 2. Modeling

“…The model used in this study was the GEOS infrastructure and atmospheric model coupled to an ocean configuration of the MITgcm, hereinafter GEOS‐MITgcm (see Light et al., 2022; Strobach et al., 2020; Strobach, Klein, et al., 2022; Strobach, Molod, et al., 2022). We used the so‐called C1440‐LLC2160 simulation, in which the GEOS atmosphere has 72 vertical layers and nominal horizontal grid spacing of 7 km, the MITgcm ocean has 90 vertical levels and horizontal grid spacing of 2–4‐km, and the simulated ocean includes full lunisolar tidal forcing (see Supporting Information and Torres et al., 2022). For this study, we extracted hourly snapshots of ocean temperature and horizontal velocity in a 15° × 15° region (18°–33°N, 75°–60°W) and 90 vertical levels for a domain size of 435 × 360 × 90 and a record of 432 days (20 January 2020–26 March 2021).…”