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Branger Karine, Drillet Yann, Houssais Marie-Nolle, Testor Pierre, Bourdall-Badie Romain, Alhammoud Bahjat, Bozec Alexandra, Mortier Laurent, Bouruet-Aubertot Pascale, Crpon Michel, . (2010). Impact of the spatial distribution of the atmospheric forcing on water mass formation in the Mediterranean Sea
. J. Geophys. Res., 115(C12), C12041–.
Abstract: The impact of the atmospheric forcing on the winter ocean convection in the Mediterranean Sea was studied with a high-resolution ocean general circulation model. The major areas of focus are the Levantine basin, the Aegean-Cretan Sea, the Adriatic Sea, and the Gulf of Lion. Two companion simulations differing by the horizontal resolution of the atmospheric forcing were compared. The first simulation (MED16-ERA40) was forced by air-sea fields from ERA40, which is the ECMWF reanalysis. The second simulation (MED16-ECMWF) was forced by the ECMWF-analyzed surface fields that have a horizontal resolution twice as high as those of ERA40. The analysis of the standard deviations of the atmospheric fields shows that increasing the resolution of the atmospheric forcing leads in all regions to a better channeling of the winds by mountains and to the generation of atmospheric mesoscale patterns. Comparing the companion ocean simulation results with available observations in the Adriatic Sea and in the Gulf of Lion shows that MED16-ECMWF is more realistic than MED16-ERA40. In the eastern Mediterranean, although deep water formation occurs in the two experiments, the depth reached by the convection is deeper in MED16-ECMWF. In the Gulf of Lion, deep water formation occurs only in MED16-ECMWF. This larger sensitivity of the western Mediterranean convection to the forcing resolution is investigated by running a set of sensitivity experiments to analyze the impact of different time-space resolutions of the forcing on the intense winter convection event in winter 1998–1999. The sensitivity to the forcing appears to be mainly related to the effect of wind channeling by the land orography, which can only be reproduced in atmospheric models of sufficient resolution. Thus, well-positioned patterns of enhanced wind stress and ocean surface heat loss are able to maintain a vigorous gyre circulation favoring efficient preconditioning of the area at the beginning of winter and to drive realistic buoyancy loss and mixing responsible for strong convection at the end of winter.
Keywords: Mediterranean Sea, deep water formation, numerical modeling, atmospheric forcing, 4504 Oceanography: Physical: Air/sea interactions, 4215 Oceanography: General: Climate and interannual variability, 4513 Oceanography: Physical: Decadal ocean variability, 4283 Oceanography: General: Water masses, 4520 Oceanography: Physical: Eddies and mesoscale processes,
Programme: 452
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Testut L, Miguez B Martin, Wppelmann G, Tiphaneau P, Pouvreau N, Karpytchev M, . (2010). Sea level at Saint Paul Island, southern Indian Ocean, from 1874 to the present
. J. Geophys. Res., 115(C12), C12028–.
Abstract: A data archeology exercise was carried out on sea level observations recorded during the transit of Venus across the Sun observed in 1874 from Saint Paul Island (3841′S, 7731 E) in the southern Indian Ocean. Historical (1874) and recent (1994–2009) sea level observations were assembled into a consistent time series. A thorough check of the data and its precise geodetic connection to the same datum was only possible thanks to the recent installation of new technologies (GPS buoy and radar water level sensor) and leveling campaigns. The estimated rate of relative sea level change, spanning the last 135 years at Saint Paul Island, was not significantly different from zero (-0.1 0.3 mm yr-1), a value which could be reconciled with estimates of global average sea level rise for the 20th century assuming the DORIS vertical velocity estimate at Amsterdam Island (100 km distant) could be applied to correct for the land motion at the tide gauge. Considering the scarcity of long-term sea level data in the Southern Hemisphere, the exercise provides an invaluable additional observational constraint for further investigations of the spatial variability of sea level change, once vertical land rates can be determined.
Keywords: sea level change, Southern Ocean, Saint Paul Island, tide gauge, historical data, 4556 Oceanography: Physical: Sea level: variations and mean, 1641 Global Change: Sea level change, 1724 History of Geophysics: Ocean sciences,
Programme: 688
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Jardon F P, Bouruet-Aubertot P, Cuypers Y, Vivier F, Lourenço A, . (2011). Internal waves and vertical mixing in the Storfjorden Polynya, Svalbard
. Journal of Geophysical Research: Oceans, 116(C12), C12040–.
Keywords: Garret and Munk model, Thorpe scale, barotropic tides, internal waves, latent heat polynya, vertical mixing, 4207 Arctic and Antarctic oceanography, 4544 Internal and inertial waves, 4572 Upper ocean and mixed layer processes,
Programme: 1015
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Ferrari Ramiro, Provost Christine, Renault Alice, Sennéchael Nathalie, Barré Nicolas, Park Young-Hyang, Lee Jae Hak, . (2012). Circulation in Drake Passage revisited using new current time series and satellite altimetry: 1. The Yaghan Basin
. JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS, 117(C12).
Keywords: 4512 Currents, 4515 Deep recirculations, 4520 Eddies and mesoscale processes, 4528 Fronts and jets, 4532 General circulation, Antarctic circumpolar current, current meter mooring, Drake Passage, eddies, meanders, Yaghan Basin,
Programme: 1061
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Shum Woodworth A., Egbert F., King K., Le Provost L.I., Molines P.R., Schlax S. & Tierney V. (1997). Accuracy asessment of recent ocean tide models. J. Geophys. Res., 102(C11), 25173–25194.
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Germe Agathe, Houssais Marie-Nolle, Herbaut Christophe, Cassou Christophe, . (2011). Greenland Sea sea ice variability over 1979–2007 and its link to the surface atmosphere
. J. Geophys. Res., 116(C10), C10034–.
Abstract: Mean winter Arctic sea ice concentration based on passive microwave observations for the period 1979–2007 are analyzed to examine the variability of the western Nordic Seas marginal ice zone (MIZ). A principal component analysis performed on this regional domain shows that the interannual variability is dominated by a mode which captures more than 70% of the total variance and shows only moderate correlation with the leading mode of global Northern Hemisphere sea ice variability. This mode appears to be related to a pattern of sea level pressure (SLP) anomaly centered on the MIZ with large scale signature resembling the canonical pattern of the North Atlantic Oscillation (NAO). Still this leading mode of SIC variability shows a weak temporal correlation with the NAO index. Taking into account the intrinsic spatial asymmetry found between the two phases of the NAO based on a weather regimes analysis, composite SIC fields are constructed which indeed suggest a preferential response of the Greenland Sea SIC variability to negative NAO-like patterns of SLP. The SLP pattern is consistent with a response of the sea ice margin to the strength of the northerly winds along eastern Greenland. A weak pattern of surface air temperature anomalies also emerges in the central Greenland Sea which occurs, at least partly, as a response of the surface atmosphere to sea ice concentrations changes. Higher order modes of winter SIC variability emerge based on a shorter winter season. One mode has much resemblance with the Odden/Nordbukta pattern while another one exhibits a significant signature in the center of the Greenland Sea convective gyre. The Odden/Nordbukta mode shows a more symmetric relation to the NAO than the leading SIC mode. Linear regression analysis consistently suggests some link between this mode and the ice area flux through Fram Strait.
Keywords: Greenland Sea, sea ice, 0750 Cryosphere: Sea ice (4540), 3339 Atmospheric Processes: Ocean/atmosphere interactions (0312, 4301, 4504), 4215 Oceanography: General: Climate and interannual variability (1616, 1635, 3305, 3309, 4513),
Programme: 452
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Vassie J.M., Harrison A.J., Woodworth P.L., Harangozo S.A., Smithson M.J. & Thompson S.R. (1994). On the temporal variability of the transport between Amsterdam and Kerguelen islands. J. Geophys. Res., 99(c1), 937–949.
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Schlichtholz P, Houssais M-N, . (2011). Forcing of oceanic heat anomalies by air-sea interactions in the Nordic Seas area
. 0148-0227, 116(C1), C01006–.
Abstract: Hydrographic data and atmospheric reanalysis from 1982 to 2005 are used to show a strong link of the Atlantic water temperature (AWT) anomalies observed in the transition zone between the Norwegian Atlantic current and the West Spitsbergen current in summer to the surface heat flux (SHF) anomalies observed over the Barents Sea open water in the preceding late winter. A mechanism proposed for this link is formation of ocean temperature anomalies in a deep mixed layer and their subsequent westward export by a branch of Atlantic water recirculating in the western Barents Sea. The SHF anomalies over the Barents Sea are due to advection of temperature and humidity by anomalous winds across the Arctic ice edge and do not strongly depend on the North Atlantic oscillation (NAO). Correlations of up to about 0.9 between the AWT anomalies and indices of atmospheric variability over the Barents Sea open prospects for seasonal AWT predictability. It is also shown that the wind-forcing responsible for positive AWT anomalies is involved in a cyclonic perturbation of the atmospheric circulation over the Nordic Seas. This perturbation generates, through influence on the sea ice distribution, a lobe of SHF anomalies in the marginal ice zone (MIZ) on the eastern (Barents Sea) and western (Greenland Sea) sides of the Nordic Seas which has the opposite sign to the open water lobe. In contrast to the Barents Sea MIZ, the diabatic heating of the atmosphere by upward SHF anomalies in the Greenland Sea MIZ competes with cold advection.
Keywords: Nordic Seas, heat anomalies, air-sea interactions, interanual variability, Atlantic water, 4215 Oceanography: General: Climate and interannual variability, 4504 Oceanography: Physical: Air/sea interactions, 4207 Oceanography: General: Arctic and Antarctic oceanography, 4263 Oceanography: General: Ocean predictability and prediction, 4572 Oceanography: Physical: Upper ocean and mixed layer processes,
Programme: 452
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Schneider J.L., B. Van Vliet-Lanoe, H.Guillou, M.Kirkbride, G.Gosselin . (2010). Morphological and sedimentological impacts of jokulhlaups in central iceland: the North-South connection. (Vol. RST2010).
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Dalton Colleen A, Ekstrm Gran, Dziewoski Adam M, . (2008). The global attenuation structure of the upper mantle
. J. Geophys. Res., 113(B9), B09303–.
Abstract: A large data set of fundamental mode Rayleigh wave amplitudes is analyzed to derive a new global three-dimensional model of shear wave attenuation in the upper mantle. The amplitude observations span a range of periods between 50 and 250 s and are derived from earthquakes with M W > 6.0 that occurred between 1993 and 2005. Four separate factors may influence an amplitude anomaly: intrinsic attenuation along the raypath, elastic focusing effects along the raypath, uncertainties in the strength of excitation, and uncertainties in the response at the station. In an earlier paper (Dalton and Ekstrm, 2006a), dependence of the retrieved attenuation structure on these terms was shown to be significant and an approach was developed to invert the amplitudes simultaneously for each term. The new three-dimensional attenuation model QRFSI12, which is the subject of this paper, is derived using this method. The model contains large lateral variations in upper-mantle attenuation, 60% to 100%, and exhibits strong agreement with surface tectonic features at depths shallower than 200 km. At greater depth, QRFSI12 is dominated by high attenuation in the southeastern Pacific and eastern Africa and low attenuation along many subduction zones in the western Pacific. Resolution tests confirm that the change in pattern of attenuation above and below 200-km depth can be determined with confidence using the fundamental mode data set. The new model is highly correlated with global models of shear wave velocity, particularly in the uppermost mantle, suggesting that the same factors may control both seismic attenuation and velocity in this depth range. However, forcing the lateral perturbations in attenuation to match those found in global velocity models decreases the data variance reduction, which suggests that subtle differences between patterns of attenuation and velocity are robust.
Keywords: Attenuation, surface waves, global seismology, 7270 Seismology: Tomography, 7260 Seismology: Theory, 7208 Seismology: Mantle, 3909 Mineral Physics: Elasticity and anelasticity, 8124 Tectonophysics: Earth's interior: composition and state,
Programme: 133
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