Impact of oceanic-scale interactions on the seasonal modulation of ocean dynamics by the atmosphere

Abstract

Ocean eddies (with a size of 100–300 km), ubiquitous in satellite observations, are known to represent about 80% of the total ocean kinetic energy. Recent studies have pointed out the unexpected role of smaller oceanic structures (with 1–50 km scales) in generating and sustaining these eddies. The interpretation proposed so far invokes the internal instability resulting from the large-scale interaction between upper and interior oceanic layers. Here we show, using a new high-resolution simulation of the realistic North Pacific Ocean, that ocean eddies are instead sustained by a different process that involves small-scale mixed-layer instabilities set up by large-scale atmospheric forcing in winter. This leads to a seasonal evolution of the eddy kinetic energy in a very large part of this ocean, with an amplitude varying by a factor almost equal to 2. Perspectives in terms of the impacts on climate dynamics and future satellite observational systems are briefly discussed.

Open-Ocean Submesoscale Motions: A Full Seasonal Cycle of Mixed Layer Instabilities from Gliders

“…This offers a higher degree of granularity than recent studies that have analyzed bulk seasonal differences in flow characteristics, which are then used to infer submesoscale activity. Both numerical models (Mensa et al 2013;Sasaki et al 2014) and observations (Callies et al 2015;Swart et al 2015;Buckingham et al 2016) provide strong evidence that there are seasonal modulations in submesoscale activity. In general, these reflect a steepening of the kinetic energy spectra during summer, typically with slopes around k…”

“Hot Spots” in the climate system—new developments in the extratropical ocean–atmosphere interaction research: a short review and an introduction

“…The wind variations thus act as a "pace maker" for the quasi-decadal KE variability by triggering its regime transition (Taguchi et al 2007). Meanwhile, modulated mesoscale eddy activity can lead to modulations in sub-mesoscale streamers and associated vertical motion (Sasaki et al 2014). …”

Zonal jets in equilibrating baroclinic instability on the polar beta‐plane: Experiments with altimetry

“…If baroclinic meanders of scale of approximately 12R d in our experiments can be considered as an analogue of oceanic mesoscale eddies (typically 100-300 km in horizontal extent), the smaller scale filaments and cyclonic eddies in the laboratory flows can be qualified as submesoscale motions. Submesoscale dynamics in the ocean (features of size 1-100 km) has been a subject of a number of recent numerical [e.g., Qiu et al, 2014;Sasaki et al, 2014] and field [e.g., Callies et al, 2015] studies. These studies showed that submesoscale eddy field is quite energetic and can significantly impact the circulation of larger scale.…”