Southern Ocean seasonal restratification delayed by submesoscale wind-front interactions
du Plessis, Marcel
Thompson, Andrew F.
MetadataShow full item record
KeywordAtmosphere-ocean interaction; Fronts; Oceanic mixed layer; In situ oceanic observations; Interannual variability; Seasonal cycle
Ocean stratification and the vertical extent of the mixed layer influence the rate at which the ocean and atmosphere exchange properties. This process has direct impacts for anthropogenic heat and carbon uptake in the Southern Ocean. Submesoscale instabilities that evolve over space (1–10 km) and time (from hours to days) scales directly influence mixed layer variability and are ubiquitous in the Southern Ocean. Mixed layer eddies contribute to mixed layer restratification, while down-front winds, enhanced by strong synoptic storms, can erode stratification by a cross-frontal Ekman buoyancy flux. This study investigates the role of these submesoscale processes on the subseasonal and interannual variability of the mixed layer stratification using four years of high-resolution glider data in the Southern Ocean. An increase of stratification from winter to summer occurs due to a seasonal warming of the mixed layer. However, we observe transient decreases in stratification lasting from days to weeks, which can arrest the seasonal restratification by up to two months after surface heat flux becomes positive. This leads to interannual differences in the timing of seasonal restratification by up to 36 days. Parameterizing the Ekman buoyancy flux in a one-dimensional mixed layer model reduces the magnitude of stratification compared to when the model is run using heat and freshwater fluxes alone. Importantly, the reduced stratification occurs during the spring restratification period, thereby holding important implications for mixed layer dynamics in climate models as well as physical–biological coupling in the Southern Ocean.
Author Posting. © American Meteorological Society, 2019. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 49(4), (2019): 1035-1053, doi:10.1175/JPO-D-18-0136.1.
The publisher requires that this item be embargoed until 2020-04-11. Please check back after 2020-04-11.
Suggested CitationArticle: du Plessis, Marcel, Swart, Sebastiaan, Ansorge, Isabelle, Mahadevan, Amala, Thompson, Andrew F., "Southern Ocean seasonal restratification delayed by submesoscale wind-front interactions", Du Plessis, M., Swart, S., Ansorge, I. J., Mahadevan, A., & Thompson, A. F. (2019). Southern Ocean seasonal restratification delayed by submesoscale wind-front interactions. Journal of Physical Oceanography, 49(4), 1035-1053, DOI:10.1175/JPO-D-18-0136.1, https://hdl.handle.net/1912/24212
Showing items related by title, author, creator and subject.
Farrell, W. E.; Berger, Jonathan; Bidlot, Jean-Raymond; Dzieciuch, Monika; Munk, Walter H.; Stephen, Ralph A.; Worcester, Peter F. (American Meteorological Society, 2016-05-10)A rapid and broadband (1 h, 1 < f < 400 Hz) increase in pressure and vertical velocity on the deep ocean floor was observed on seven instruments comprising a 20-km array in the northeastern subtropical Pacific. The authors ...
Slater, Donald; Straneo, Fiamma; Das, Sarah B.; Richards, Clark G.; Wagner, Till (American Geophysical Union, 2018-11-15)Recent acceleration of Greenland's ocean‐terminating glaciers has substantially amplified the ice sheet's contribution to global sea level. Increased oceanic melting of these tidewater glaciers is widely cited as the likely ...
Yu, Lisan; Jin, Xiangze; Weller, Robert A. (American Meteorological Society, 2007-07-01)This study investigated the accuracy and physical representation of air–sea surface heat flux estimates for the Indian Ocean on annual, seasonal, and interannual time scales. Six heat flux products were analyzed, including ...