Nelson, A. D., Arbic, B. K., Zaron, E. D., Savage, A. C., Richman, J. G., Buijsman, M. C., et al. (2019). Toward Realistic Nonstationarity of Semidiurnal Baroclinic Tides in a Hydrodynamic Model. J. Geophys. Res. Oceans , 124 (9), 6632–6641.
Abstract: Semidiurnal baroclinic tide sea surface height (SSH) variance and semidiurnal nonstationary variance fraction (SNVF) are compared between a hydrodynamic model and altimetry for the low- to middle-latitude global ocean. Tidal frequencies are aliased by similar to 10-day altimeter sampling, which makes it impossible to unambiguously identify nonstationary tidal signals from the observations. In order to better understand altimeter sampling artifacts, the model was analyzed using its native hourly outputs and by subsampling it in the same manner as altimeters. Different estimates of the semidiurnal nonstationary and total SSH variance are obtained with the model depending on whether they are identified in the frequency domain or wave number domain and depending on the temporal sampling of the model output. Five sources of ambiguity in the interpretation of the altimetry are identified and briefly discussed. When the model and altimetry are analyzed in the same manner, they display qualitatively similar spatial patterns of semidiurnal baroclinic tides. The SNVF typically correlates above 80% at all latitudes between the different analysis methods and above 60% between the model and altimetry. The choice of analysis methodology was found to have a profound effect on estimates of the semidiurnal baroclinic SSH variance with the wave number domain methodology underestimating the semidiurnal nonstationary and total SSH variances by 68% and 66%, respectively. These results produce a SNVF estimate from altimetry that is biased low by a factor of 0.92. This bias is primarily a consequence of the ambiguity in the separation of tidal and mesoscale signals in the wave number domain.
Neto, A. G., Palter, J., Bower, A., Furey, H., & Xu. X. (2020). Labrador Sea Water transport across the Charlie-Gibbs Fracture Zone. J. Geophys. Res. Oceans , Accepted .
Abstract: Labrador Sea Water (LSW) is a major component of the deep limb of the Atlantic Meridional Overturning Circulation, yet LSW transport pathways and their variability lack a complete description. A portion of the LSW exported from the subpolar gyre is advected eastward along the North Atlantic Current and must contend with the Mid‐Atlantic Ridge before reaching the eastern basins of the North Atlantic. Here, we analyze observations from a mooring array and satellite altimetry, together with outputs from a hindcast ocean model simulation, to estimate the mean transport of LSW across the Charlie Gibbs Fracture Zone (CGFZ), a primary gateway for the eastward transport of the water mass. The LSW transport estimated from the 25‐year altimetry record is 5.3 ± 2.9 Sv, where the error represents the combination of observational variability and the uncertainty in the projection of the surface velocities to the LSW layer. Current velocities modulate the interannual to higher frequency variability of the LSW transport at the CGFZ, while the LSW thickness becomes important on longer time scales. The modeled mean LSW transport for 1993‐2012 is higher than the estimate from altimetry, at 8.2 ± 4.1 Sv. The modeled LSW thickness decreases substantially at the CGFZ between 1996 and 2009, consistent with an observed decline in LSW volume in the Labrador Sea after 1994. We suggest that satellite altimetry and continuous hydrographic measurements in the central Labrador Sea, supplemented by profiles from Argo floats, could be sufficient to quantify the LSW transport at the CGFZ.
Nguyen, T. T. (2014). Variability of Cross-Slope Flow in the Desoto Canyon Region . Master's thesis, Florida State University, Tallahassee, FL.
Nguyen, T. - T., Morey, S. L., Dukhovskoy, D. S., & Chassignet, E. P. (2015). Nonlocal impacts of the Loop Current on cross-slope near-bottom flow in the northeastern Gulf of Mexico. Geophys. Res. Lett. , 42 (8), 2926–2933.
Nielsen, E. R., Schumacher, R. S., & Keclik, A. M. (2016). The Effect of the Balcones Escarpment on Three Cases of Extreme Precipitation in Central Texas. Mon. Wea. Rev. , 144 (1), 119–138.
Nof, D., Jia, Y., Chassignet, E., & Bozec, A. (2011). Fast Wind-Induced Migration of Leddies in the South China Sea. J. Phys. Oceanogr. , 41 (9), 1683–1693.
Nof, D., Zharkov, V., Arruda, W., Pichevin, T., Van Gorder, S., & Paldor, N. (2012). Comments on “On the Steadiness of Separating Meandering Currents”. J. Phys. Oceanogr. , 42 (8), 1366–1370.
Nof, D., Zharkov, V., Ortiz, J., Paldor, N., Arruda, W., & Chassignet, E. (2011). The arrested Agulhas retroflection. J Mar Res , 69 (4), 659–691.
Noska, R., & Misra, V. (2016). Characterizing the onset and demise of the Indian summer monsoon. Geophys. Res. Lett. , 43 (9), 4547–4554.
Nunes, A. M. B., & Cocke, S. (2004). Implementing a physical initialization procedure in a regional spectral model: impact on the short-range rainfall forecasting over South America. Tellus A , 56 (2), 125–140.
