Journal of Geophysical Research: Oceans

Conceptual illustration of fluid mud formation and entrainment in troughs of subtidal dunes in an estuarine turbidity zone. Stage I, II, and III show the accumulation of suspended sediment and fluid mud formation during slack water. Stage IV is governed by velocity shear. Stage V depicts the transition from the influence of shear to entrainment, which occurs during stage VI. The dune-specific distribution of currents and turbulence in the lee-side is sketched in stage VII, with flow oriented in dune direction. Values of current velocity and suspended sediment concentration correspond to the beginning of each stage. Time is hours after slack water.

Global maps of time-averaged zonal geostrophic velocity, u¯, estimated from (a) observed and (b) simulated SSH, 1993–1996. Observed SSH consist of AVISO/CLS ADT and were spatially high-pass-filtered prior to estimating zonal geostrophic velocity. Simulated SSH were obtained by superimposing Gaussian eddies with amplitude, scale, position, and lifetime identically specified by the eddy database [CCS2011] onto an otherwise flat ocean. Black boxes denote the region examined in this study (20°S–50°S, 200°E–280°E).

Climatological cooling inhibition index (CI; in (J.m−2)−1/3) for (a and d) premonsoon and (b and e) postmonsoon seasons, and (c and f) their difference using (top) observations and (bottom) the model over the 1978–2007 period. The thick contour delineates a region where 80% of TCs occur in the northern Indian Ocean (see Figure 1) while dashed colored boxes on Figure 6c are same as in Figure 3. The black dashed line indicates the temperature and salinity section at 90°E shown on Figure 5.

Derivation of bloom detection products (figures c and f) from 8-day composite MODIS-Aqua chlorophyll-a (CHL, top row, figures a and b) and fluorescence line height (FLH, bottom row, figures d and e) imagery at ~1.1 kilometer resolution. Bloom products are created by subtracting a “reference” composite (b and e; 15-22 September 2009) from a “current” composite (a and d; 23-30 September 2009), then normalizing to the reference. Resulting c) CHLrel and f) FLHrel bloom product imagery displays the pixel-by-pixel relative percent change observed in CHL or FLH over a 16-day time frame. Anomaly coloration is employed with positive relative differences in shades of red and negative differences in shades of blue. White indicates pixels lacking data due to quality-control flags. Figures c) and f) are overlaid with 0.25º (~28 km) resolution sea surface height (SSH) anomaly contours at 2-centimeter intervals for the week of September 26th, 2009 (http://las.pfeg.noaa.gov/oceanWatch/oceanwatch.php). Notable features in c) and f) include bloom signals coincident with alongshore depressed SSH, an indicator of coastal upwelling, and offshore mesoscale circulation features.

Mean and variance ellipses of the altimetrically derived surface velocities and the insitu velocities over the three-year period: from 21 January 2006 to 1 April 2009. Surface velocities derived from MADT are shown by solid yellow lines and those derived from Jason-1 track data are shown by dashed yellow lines. M2 is not at an intersection of two Jason tracks and therefore no velocities have been computed from Jason-1 track data. Means and ellipses at different depths of the in-situ velocities are plotted in red for 500 m depth, green for 1000 m depth and blue for depths greater than 2000 m. Time resolution is 1 day for in situ velocities, 7 days for MADT-based velocities, and 10 days for Jason-1 track-based velocities. Bottom topography.

The first mode of cyclostationary empirical orthogonal function, and the corresponding principal component (PC) time series of the bottom pressure at Kuroshio Extension System Study (KESS) sites. Daily maps (days 1–13) and KESS bottom pressure plot show physical evolution of near 13 day variability at the 15 sites. The strength of the physical evolution depicted in the spatial patterns varies during the observation period, according to the PC time series plot.

Total downstream velocity (left) before and (right) after the winter 2007–2008. These conditions are typical of all periods when PC1 is large and positive (mean + EOF1) or large and negative (mean − EOF1).