Menezes Viviane V.

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Viviane V.

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Now showing 1 - 5 of 5
  • Article
    Accelerated freshening of Antarctic Bottom Water over the last decade in the Southern Indian Ocean
    (American Association for the Advancement of Science, 2017-01-25) Menezes, Viviane V. ; Macdonald, Alison M. ; Schatzman, Courtney
    Southern Ocean abyssal waters, in contact with the atmosphere at their formation sites around Antarctica, not only bring signals of a changing climate with them as they move around the globe but also contribute to that change through heat uptake and sea level rise. A repeat hydrographic line in the Indian sector of the Southern Ocean, occupied three times in the last two decades (1994, 2007, and, most recently, 2016), reveals that Antarctic Bottom Water (AABW) continues to become fresher (0.004 ± 0.001 kg/g decade−1), warmer (0.06° ± 0.01°C decade−1), and less dense (0.011 ± 0.002 kg/m3 decade−1). The most recent observations in the Australian-Antarctic Basin show a particularly striking acceleration in AABW freshening between 2007 and 2016 (0.008 ± 0.001 kg/g decade−1) compared to the 0.002 ± 0.001 kg/g decade−1 seen between 1994 and 2007. Freshening is, in part, responsible for an overall shift of the mean temperature-salinity curve toward lower densities. The marked freshening may be linked to an abrupt iceberg-glacier collision and calving event that occurred in 2010 on the George V/Adélie Land Coast, the main source region of bottom waters for the Australian-Antarctic Basin. Because AABW is a key component of the global overturning circulation, the persistent decrease in bottom water density and the associated increase in steric height that result from continued warming and freshening have important consequences beyond the Southern Indian Ocean.
  • Article
    Surface heat fluxes over the northern Arabian Gulf and the northern Red Sea: Evaluation of ECMWF-ERA5 and NASA-MERRA2 reanalyses
    (MDPI, 2019-08-28) Al Senafi, Fahad ; Anis, Ayal ; Menezes, Viviane V.
    The air–sea heat fluxes in marginal seas and under extreme weather conditions constitute an essential source for energy transport and mixing dynamics. To reproduce these effects in numerical models, we need a better understanding of these fluxes. In response to this demand, we undertook a study to examine the surface heat fluxes in the Arabian Gulf (2013 to 2014) and Red Sea (2008 to 2010)—the two salty Indian Ocean marginal seas. We use high-quality buoy observations from offshore meteorological stations and data from two reanalysis products, the Modern-Era Retrospective analysis for Research and Applications version 2 (MERRA2) from the National Aeronautics and Space Administration (NASA) and ERA5, the fifth generation of the European Centre for Medium-Range Weather Forecasts (ECMWF) atmospheric reanalyses of global climate. Comparison of the reanalyses with the in situ-derived fluxes shows that both products underestimate the net heat fluxes in the Gulf and the Red Sea, with biases up to −45 W/m 2 in MERRA2. The reanalyses reproduce relatively well the seasonal variability in the two regions and the effects of wind events on air–sea fluxes. The results suggest that when forcing numerical models, ERA5 might provide a preferable dataset of surface heat fluxes for the Arabian Gulf while for the Red Sea the MERRA2 seems preferable.
  • Article
    Evaporative implications of dry-air outbreaks over the northern Red Sea.
    (American Geophysical Union, 2019-04-01) Menezes, Viviane V. ; Farrar, J. Thomas ; Bower, Amy S.
    We investigate the impacts of westward wind events on the Red Sea evaporation using the 35‐year second Modern‐Era Retrospective analysis for Research and Applications reanalysis and a 2‐year‐long record of in situ observations from a heavily instrumented air‐sea interaction mooring. These events are common during boreal winter, and their effects are similar to cold‐air outbreaks that occur in midpolar and subpolar latitudes. They cause extreme heat loss from the sea, which is dominated by latent heat fluxes. Different from cold‐air outbreaks, the intensified heat loss is due to the low relative humidity as we show through latent heat flux decomposition. Rainfall is negligible during these events, and we refer to them as dry‐air outbreaks. We also investigate the general atmospheric circulation pattern that favors their occurrence, which is associated with an intensified Arabian High at the north‐central portion of the Arabian Peninsula—a feature that seems to be an extension of the Siberian High. The analyses reveal that the westward winds over the northern Red Sea and the winter Shamal winds in the Persian Gulf are very likely to be part of the same subsynoptic‐scale feature. The second Modern‐Era Retrospective analysis for Research and Applications reanalysis indicates that the occurrence of westward wind events over the northern Red Sea has grown from 1980 to 2015, especially the frequency of large‐scale events, the cause of which is to be investigated. We hypothesize that dry‐air outbreaks may induce surface water mass transformation in the surface Red Sea Eastern Boundary Current and could represent a significant process for the oceanic thermohaline‐driven overturning circulation.
  • Article
    Interannual variability of the South Indian Countercurrent
    (John Wiley & Sons, 2016-05-26) Menezes, Viviane V. ; Phillips, Helen E. ; Vianna, Marcio L. ; Bindoff, Nathaniel L.
    In the present work, we investigate the interannual variability of the South Indian Countercurrent (SICC), a major and still understudied current of the Indian Ocean circulation. To characterize the interannual variability of the SICC, four different data sets (altimetry, GLORYS, OFAM3, and SODA) are analyzed using multiple tools, which include Singular Spectrum Analysis and wavelet methods. The quasi-biennial band dominates the SICC low-frequency variance, with the main peak in the 1.5–1.8 year interval. A secondary peak (2.1–2.5 year) is only found in the western basin. Interannual and decadal-type modulations of the quasi-biennial signal are also identified. In addition, limitations of SODA before the 1960s in the SICC region are revealed. Within the quasi-biennial band, the SICC system presents two main patterns with a multiple jet structure. One pattern is characterized by a robust northern jet, while in the other the central jet is well developed and northern jet is weaker. In both patterns, the southern jet has always a strong signature. When the northern SICC jet is stronger, the northern cell of the subtropical gyre has a triangular shape, with its southern limb having a strong equatorward slant. The quasi-biennial variability of the SICC is probably related to the Indian Ocean tropical climate modes that are known to have a strong biennial characteristic.
  • Article
    Westward mountain-gap wind jets of the northern Red Sea as seen by QuikSCAT
    (Elsevier, 2018-03-19) Menezes, Viviane V. ; Farrar, J. Thomas ; Bower, Amy S.
    We analyse ten years of QuikSCAT satellite surface winds to statistically characterize the spatio-temporal variability of the westward mountain-gap wind jets over the northern Red Sea. These wind jets bring relatively cold and dry air from the Arabian Desert, increasing heat loss and evaporation over the region similar to cold-air outbreaks from mid and subpolar latitudes. QuikSCAT captures the spatial structure of the wind jets and agrees well with in situ observations from a heavily instrumented mooring in the northern Red Sea. The local linear correlations between QuikSCAT and in situ winds are 0.96 (speed) and 0.85 (direction). QuikSCAT also reveals that cross-axis winds such as the mountain-gap wind jets are a major component of the regional wind variability. The cross-axis wind pattern appears as the second (or third) mode in the four vector Empirical Orthogonal Function analyses we performed, explaining between 6% to 11% of the wind variance. Westward wind jets are typical in winter, especially in December and January, but with strong interannual variability. Several jets can occur simultaneously and cover a large latitudinal range of the northern Red Sea, which we call large-scale westward events. QuikSCAT recorded 18 large-scale events over ten years, with duration between 3 to 8 days and strengths varying from 3–4 to 9–10 m/s. These events cause large changes in the wind stress curl pattern, imposing a remarkable sequence of positive and negative curl along the Red Sea main axis, which might be a wind forcing mechanism for the oceanic mesoscale circulation.