FN Archimer Export Format
PT J
TI The Annual Cycle of Upper-Ocean Potential Vorticity and Its Relationship to Submesoscale Instabilities
BT 
AF YU, Xiaolong
   Naveira GARABATO, Alberto C.
   MARTIN, Adrian P.
   MARSHALL, David P.
AS 1:1;2:2,3;3:3;4:4;
FF 1:PDG-ODE-LOPS-OH;2:;3:;4:;
C1 Univ Brest, IFREMER, CNRS, IRD,Lab Oceanog Phys & Spatiale,IUEM, Brest, France.
   Univ Southampton, Ocean & Earth Sci, Southampton, Hants, England.
   Natl Oceanog Ctr, Southampton, Hants, England.
   Univ Oxford, Dept Phys, Oxford, England.
C2 IFREMER, FRANCE
   UNIV SOUTHAMPTON, UK
   NOC, UK
   UNIV OXFORD, UK
SI BREST
SE PDG-ODE-LOPS-OH
UM LOPS
IN WOS Ifremer UMR
   copubli-europe
IF 3.806
TC 9
UR https://archimer.ifremer.fr/doc/00698/81014/85016.pdf
LA English
DT Article
DE ;North Atlantic Ocean;Instability;Potential vorticity;Mixed layer;In situ oceanic observations;Time series
AB The evolution of upper-ocean potential vorticity (PV) over a full year in a typical midocean area of the northeast Atlantic is examined using submesoscale- and mesoscale-resolving hydrographic and velocity measurements from a mooring array. A PV budget framework is applied to quantitatively document the competing physical processes responsible for deepening and shoaling the mixed layer. The observations reveal a distinct seasonal cycle in upper-ocean PV, characterized by frequent occurrences of negative PV within deep (up to about 350 m) mixed layers from winter to mid-spring, and positive PV beneath shallow (mostly less than 50 m) mixed layers during the remainder of the year. The cumulative positive and negative subinertial changes in the mixed layer depth, which are largely unaccounted for by advective contributions, exceed the deepest mixed layer by one order of magnitude, suggesting that mixed layer depth is shaped by the competing effects of destratifying and restratifying processes. Deep mixed layers are attributed to persistent atmospheric cooling from winter to mid-spring, which triggers gravitational instability leading to mixed layer deepening. However, on shorter time scales of days, conditions favorable to symmetric instability often occur as winds intermittently align with transient frontal flows. The ensuing submesoscale frontal instabilities are found to fundamentally alter upper-ocean turbulent convection, and limit the deepening of the mixed layer in the winter-to-mid-spring period. These results emphasize the key role of submesoscale frontal instabilities in determining the seasonal evolution of the mixed layer in the open ocean. 
PY 2021
PD JAN
SO Journal Of Physical Oceanography
SN 0022-3670
PU Amer Meteorological Soc
VL 51
IS 2
UT 000646377800007
BP 385
EP 402
DI 10.1175/JPO-D-20-0099.1
ID 81014
ER

EF