PT Unknown
AU Rath, W
TI The Influence of Ocean-Surface-Velocity-Dependent Wind Stress on the Dynamics of the Southern Ocean: the Near-Inertial and the Sub-Inertial Response
PY 2013
PU Christian-Albrechts-Universität zu Kiel
WP https://macau.uni-kiel.de/receive/diss_mods_00013692
LA en
DE Near-Inertial Oscillations; Ocean Modelling; Wind Forcing; Traegheitswellen; Ozeanmodelle; Wind-Antrieb
AB This thesis examines the consequences of the ocean-surface-velocity
dependence of the wind stress (SVD) for the dynamics of the Southern Ocean.  It
does so by comparing the output from eddying ocean-model experiments that only
differ in the way the wind stress is parameterized.  The thesis consists of
three separate research papers.

The first paper assesses the influence of SVD on the near-inertial variability.
It is shown that SVD leads to a substantial reduction of horizontally averaged
near-inertial energy (NIE) and of horizontally averaged wind power input (WPI)
into the near-inertial frequency band.  The observed reduction of NIE and
near-inertial WPI is explained by the fact that SVD, to leading order, adds a
linear damping term to the momentum equation governing near-inertial
oscillations in the mixed-layer.  This damping term is inversely proportional
to the mixed-layer depth and hence the effect of SVD on near-inertial
oscillations is found to be largest if the mixed-layer is shallow.

The second paper assesses the influence of SVD on sub-inertial time scales.  It
is found that SVD also substantially reduces sub-inertial WPI and mesoscale
eddy kinetic energy (EKE).  The largest effect of SVD on sub-inertial WPI and
EKE is found along the path of the Antarctic Circumpolar Current (ACC).  SVD is
found to generally damp the amplitude of monthly to inter-annual variability in
the model, without affecting the time-dependence of the wind stress, of WPI,
and of the strength of the ACC.  SVD is, however, found to have only a minor
impact on the path and strength of the ACC.

The third paper connects to the first one by focussing on the spatial and
temporal distribution of NIE and near-inertial WPI in the Southern Ocean.  The
modelled near-inertial WPI is found to be mainly governed by the variability of
the wind-stress at the local inertial frequency (IWSV).  This relationship is
used to indirectly examine the temporal evolution of near-inertial WPI on time
scales much longer than those which can be directly examined with the model.
It is found that from 1979 to 2011 IWSV over the Southern Ocean has increased
substantially.  Furthermore, the inter-annual variability of IWSV in the
Southern Ocean is shown to be largely governed by the Southern Annular Mode.
PI Kiel
ER