202 research outputs found
The role of wind gusts in upper ocean diurnal variability
Upper ocean processes play a key role in air-sea coupling, with variability on both short and long time scales. The diurnal cycle associated with diurnal solar insolation and nighttime cooling, may act, along with stochastic wind variability, on upper ocean temperatures and stratification resulting in a diurnal warm layer and a nonlinear rectified effect on longer time scales. This study describes diurnal changes in upper ocean temperature for a location in the equatorial Indian Ocean, using observations from the Dynamics of the Madden-Julian Oscillation field campaign, a high vertical resolution 1-D process model, and a diurnal cycling scheme. Solar forcing is the main driver of diurnal variability in upper ocean temperature and stratification. Yet except during nighttime convection, winds with variability on the order of hours (here referred to as “wind gusts”) regulate how fast surface water is mixed to greater depths when daily mean winds are weak. Wind gusts are much stronger than diurnal winds. Even using stochastic wind gusts but no diurnal winds as input in a 1-D process model yields an estimate of diurnal temperature that compares well with observations. A new version of the Large and Caron (2015) scheme (LC2015) provides an estimate of upper ocean diurnal temperature that is consistent with observations. LC2015 has the advantage of being suitable for implementation in a climate model, with the goal to improve SST estimates, hence the simulated heat flux at the air-sea interface. Yet LC2015 is not very sensitive to the inclusion or omission of the high-frequency component of the wind
Connections between ocean bottom topography and Earth’s climate
Author Posting. © Oceanography Society, 2004. This article is posted here by permission of Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 17, 1 (2004): 65-74.The seafloor is one of the critical controls on the
ocean’s general circulation. Its influence comes through
a variety of mechanisms including the contribution of
mixing in the ocean’s interior through the generation of
internal waves created by currents flowing over rough
topography. The influence of topographic roughness on
the ocean’s general circulation occurs through a series
of connected processes. First, internal waves are generated
by currents and tides flowing over topographic
features in the presence of stratification. Some portion
of these waves is sufficiently nonlinear that they immediately
break creating locally enhanced vertical mixing.
The majority of the internal waves radiate away from
the source regions, and likely contribute to the background
mixing observed in the ocean interior. The
enhancement of vertical mixing over regions of rough
topography has important implications for the abyssal
stratification and circulation. These in turn have implications
for the storage and transport of energy in the climate
system, and ultimately the response of the climate
system to natural and anthropogenic forcing. Finally,
mixing of the stratified ocean leads to changes in sea
level; these changes need to be considered when predicting
future sea level.SRJ
was supported by the National Science Foundation
under grant OCE-0241061 and an Office of Naval
Research Young Investigator Award, LCS was supported
by the Office of Naval Research under grant
N00014-03-1-0307, and STG was supported by the
National Science Foundation under grant OCE-
9985203/OCE-0049066 and by the National
Aeronautics and Space Administration under JPL contract
1224031
Surface salinity under transitioning ice cover in the Canada Basin: Climate model biases linked to vertical distribution of fresh water
The Canada Basin has exhibited a significant trend toward a fresher surface layer and thus a more stratified upper-ocean over the past three decades. State-of-the-art ice-ocean models, by contrast, tend to simulate a surface layer that is saltier and less stratified than observed. Here, we examine decadal changes to seasonal processes that may contribute to this wide-reaching model bias using climate model simulations from the Community Earth System Model and below-ice observations from the Arctic Ice Dynamics Joint Experiment in 1975 and Ice Tethered Profilers in 2006-2012. In contrast to the observations, the models simulate salinity profiles that show relatively little variation between 1975 and 2012. We demonstrate that this bias can be mainly attributed to unrealistically deep vertical mixing in the model, creating a surface layer that is saltier than observed. The results provide insight for climate model improvement with broad implications for Arctic sea ice and ecosystem dynamics
Recent Southern Ocean warming and freshening driven by greenhouse gas emissions and ozone depletion
HIRDLS poster
A poster supporting the HIRDLS data held at the BADC (High Resolution Dynamics Limb Sounder (HIRDLS) instrument)
Fitness benefits of prolonged post-reproductive lifespan in women
Most animals reproduce until they die, but in humans, females can survive long after ceasing reproduction. In theory, a prolonged post-reproductive lifespan will evolve when females can gain greater fitness by increasing the success of their offspring than by continuing to breed themselves. Although reproductive success is known to decline in old age, it is unknown whether women gain fitness by prolonging lifespan post-reproduction. Using complete multi-generational demographic records, we show that women with a prolonged post-reproductive lifespan have more grandchildren, and hence greater fitness, in pre-modern populations of both Finns and Canadians. This fitness benefit arises because post-reproductive mothers enhance the lifetime reproductive success of their offspring by allowing them to breed earlier, more frequently and more successfully. Finally, the fitness benefits of prolonged lifespan diminish as the reproductive output of offspring declines. This suggests that in female humans, selection for deferred ageing should wane when one's own offspring become post-reproductive and, correspondingly, we show that rates of female mortality accelerate as their offspring terminate reproduction
Oceanic Heat Delivery to the Antarctic Continental Shelf: Large-Scale, Low-Frequency Variability
The response of the Antarctic Circumpolar Current to recent climate change
Observations show a significant intensification of the Southern Hemisphere westerlies, the prevailing winds between the latitudes of 30° and 60° S, over the past decades. A continuation of this intensification trend is projected by climate scenarios for the twenty-first century. The response of the Antarctic Circumpolar Current and the carbon sink in the Southern Ocean to changes in wind stress and surface buoyancy fluxes is under debate. Here we analyse the Argo network of profiling floats and historical oceanographic data to detect coherent hemispheric-scale warming and freshening trends that extend to depths of more than 1,000 m. The warming and freshening is partly related to changes in the properties of the water masses that make up the Antarctic Circumpolar Current, which are consistent with the anthropogenic changes in heat and freshwater fluxes suggested by climate models. However, we detect no increase in the tilt of the surfaces of equal density across the Antarctic Circumpolar Current, in contrast to coarse-resolution model studies. Our results imply that the transport in the Antarctic Circumpolar Current and meridional overturning in the Southern Ocean are insensitive to decadal changes in wind stress
Evidence Based Development of a Novel Lateral Fibula Plate (VariAx Fibula) Using a Real CT Bone Data Based Optimization Process During Device Development
Development of novel implants in orthopaedic trauma surgery is based on limited datasets of cadaver trials or artificial bone models. A method has been developed whereby implants can be constructed in an evidence based method founded on a large anatomic database consisting of more than 2.000 datasets of bones extracted from CT scans. The aim of this study was the development and clinical application of an anatomically pre-contoured plate for the treatment of distal fibular fractures based on the anatomical database
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