Variability of clay mineral assemblages in the Western Pacific Warm Pool(WPWP) over the past 370 ka shows the prominent glacial-interglacial cyclicity.Smectite(62%-91%) is the dominant clay mineral,with decreased contents during interglacials while increased in glacials.In contrast,variations in chlorite(4%-21%),illite(4%-12%),and kaolinite(2%-10%) share a similar pattern with higher contents during interglacials than glacials,mirroring to that of smectite.The results indicate that the smectite-dominated clay minerals derive mainly from the river detrital inputs of New Guinea.The glacial-interglacial cycle of clay mineral assemblages well correspond to the fluctuation of sea level.When the sea level was low,the river materials can travel more easily across the narrow shelf off the island of New Guinea,inject directly into the subsurface currents flowing westwards,then merge into the Equatorial Undercurrent(EUC),and eventually deposit on the central part of WPWP.Precessional periods of the smectite content indicate the intensity of mechanical erosion in its provenance of New Guinea,responding to the river runoff and precipitation,and this could also be linked to the meridional migration of the Intertropical Convergence Zone(ITCZ).
The temporal and spatial evolution of a deep-reaching anticyclonic eddy(AE) is studied using a combination of satellite measurements, moored observations and ocean model reanalysis data in the South China Sea(SCS). Three evolutionary stages in eddy's lifecycle are identified from changes in eddy dynamical characteristics estimated from satellite altimetry: birth(22 days), growth(64 days), and decay(47 days). Similar patterns are also distinguished from dynamic signals in HYCOM.Further, flows reversal and upwelling of cold water below 1500 m were captured by the in-situ records when this energetic,highly nonlinear and long-lived(over 19 weeks) AE passed by our mooring position. Its detailed vertical structure is examined through temperature anomalies, vertical shear of horizontal velocities, and horizontal streamlines estimated from ocean model reanalysis data. Results from the model reveal a mesoscale AE with first-mode baroclinic structure: a bowl-shaped anticyclonic flow in the upper ocean connected to a slant-cylinder cyclonic flow at depth, with a transition layer at depths between 400 and 700 m. It is in good agreement with moored observations but showing a shallower transition depth, suggesting a slight deficiency in the model due to limited deep-sea observations. Last, we estimate eddy heat transport at different depths and stages along the AE's path based on the model data. The result reveals that pronounced heat fluxes occur during growth stage(depths <400 m),counting for 73.03% of the total value. In the decay stage, major heat transport occurs at deeper depth(depths >700–1500 m).Dynamical characteristics suggest that the vertical structure and temporal evolution of the eddy play significant roles in basinscale movement and heat transferring. Considering that mesoscale eddies are ubiquitous in the SCS, our results support a recently-proposed mechanism, whereby upper ocean flows produce changes in the deep-sea circulation, potentially influencing boundary layer dynamics. For the first time to track and
Meng WANGYanwei ZHANGZhifei LIUYulong ZHAOJianru LI
