TY - JOUR

T1 - Evolution of Oceanic Near Surface Stratification in Response to an Autumn Storm

AU - Lucas, Natasha

AU - Grant, Alan Laurence Michael

AU - Rippeth, Tom

AU - Polton, Jeff

AU - Palmer, Matthew

AU - Brannigan, Liam

AU - Belcher, Stephen E.

N1 - © Copyright [09/10/19] American Meteorological Society (AMS). Permission to use figures, tables, and brief excerpts from this work in scientific and educational works is hereby granted provided that the source is acknowledged. Any use of material in this work that is determined to be “fair use” under Section 107 of the U.S. Copyright Act or that satisfies the conditions specified in Section 108 of the U.S. Copyright Act (17 USC §108) does not require the AMS’s permission. Republication, systematic reproduction, posting in electronic form, such as on a website or in a searchable database, or other uses of this material, except as exempted by the above statement, requires written permission or a license from the AMS. All AMS journals and monograph publications are registered with the Copyright Clearance Center (http://www.copyright.com). Questions about permission to use materials for which AMS holds the copyright can also be directed to permissions@ametsoc.org. Additional details are provided in the AMS Copyright Policy statement, available on the AMS website (http://www.ametsoc.org/CopyrightInformation).

PY - 2019/11

Y1 - 2019/11

N2 - Understanding the processes that control the evolution of the ocean surface boundary layer (OSBL) is a prerequisite for obtaining accurate simulations of the effects of air-sea interaction on the ocean. Observations of the rate of dissipation of turbulent kinetic energy (ɛ), temperature, salinity, current structure and wave-field over a period of 9.5 days in the NE Atlantic during the Ocean Surface Mixing, Ocean Submesoscale Interaction Study (OSMOSIS), are presented. The focus of this study is a storm which passed over the observational area during this period.The profiles of ɛ in the OSBL are consistent with profiles from large eddy simulation (LES) of Langmuir turbulence. In the transition layer (TL), at the base of the OSBL, ɛ was found to vary periodically at the local inertial frequency. A simple bulk model of the OSBL, and a parametrisation of shear driven turbulence in the TL, are developed. The parametrisation of ɛ is based on assumptions about the momentum balance of the OSBL and shear across the TL. The predicted rate of deepening, heat budget and the inertial currents in the OSBL were in good agreement with the observations, as is the agreement between ɛ from the parametrisation, and the observed dissipation rate in the TL. A previous study reports spikes of elevated dissipation related to enhanced shear at the base of the OSBL after this storm. These spikes are not predicted by this new parametrisation suggesting that they are generated through a different mechanism which will be discussed.

AB - Understanding the processes that control the evolution of the ocean surface boundary layer (OSBL) is a prerequisite for obtaining accurate simulations of the effects of air-sea interaction on the ocean. Observations of the rate of dissipation of turbulent kinetic energy (ɛ), temperature, salinity, current structure and wave-field over a period of 9.5 days in the NE Atlantic during the Ocean Surface Mixing, Ocean Submesoscale Interaction Study (OSMOSIS), are presented. The focus of this study is a storm which passed over the observational area during this period.The profiles of ɛ in the OSBL are consistent with profiles from large eddy simulation (LES) of Langmuir turbulence. In the transition layer (TL), at the base of the OSBL, ɛ was found to vary periodically at the local inertial frequency. A simple bulk model of the OSBL, and a parametrisation of shear driven turbulence in the TL, are developed. The parametrisation of ɛ is based on assumptions about the momentum balance of the OSBL and shear across the TL. The predicted rate of deepening, heat budget and the inertial currents in the OSBL were in good agreement with the observations, as is the agreement between ɛ from the parametrisation, and the observed dissipation rate in the TL. A previous study reports spikes of elevated dissipation related to enhanced shear at the base of the OSBL after this storm. These spikes are not predicted by this new parametrisation suggesting that they are generated through a different mechanism which will be discussed.

KW - Boundary layer

KW - Diapycnal mixing

KW - Langmuir circulation

KW - Oceanic mixed layer

KW - Thermocline

U2 - 10.1175/JPO-D-19-0007.1

DO - 10.1175/JPO-D-19-0007.1

M3 - Article

VL - 49

SP - 2961

EP - 2978

JO - Journal of Physical Oceanography

JF - Journal of Physical Oceanography

SN - 0022-3670

IS - 11

ER -