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A new depositional model for hummocky cross-stratified sandstones is based on the following observations. (1) Storms transport coastal sand to the inner shell under oscillatory-dominant combined flows exerting peak instantaneous bed shear stresses roughly normal to shore. (2) Isotropic hummocky cross-stratification is formed experimentally by large, three-dimensional, symmetrical bed forms generated by long-period, purely oscillatory flow and very strongly oscillatory-dominant combined flow. Anisotropic hummocky cross-stratification is formed by strongly oscilatory-dominant flow. (3) Grain fabric in hummocky sandstones indicates rapid reversals of bed shear stress consistent with deposition shore-normal oscillatory flow, initially superimposed on a relatively weak bottom current with a seaward-directed component of motion. Thus, shore-normal transport of coarse bedload on the inner shelf during storms (inferred from studies of ancient units) is caused by the interaction of high-speed oscillatory bottom motions under long-period shoaling waves and a relatively slow shore-oblique bottom current driven by geostrophically balanced coastal downwelling. Turbidity currents are not required to form shore-normal paleoflow indicators from hummocky beds. Large three-dimensional wave ripples generated by waning-storm or swell waves are responsible for much of the hummocky cross-stratification in the stratigraphic record.

Assessing changes in the marine carbon cycle arising from anthropogenic CO2 emissions requires a detailed understanding of the carbonate system's natural variability. Coastal ecosystems vary over short spatial and temporal scales, so their dynamics are not well-described by long-term and broad regional averages. A year-long time series of pCO2, temperature, salinity, and currents is used to quantify the high-frequency variability of the carbonate system at the mouth of the Bay of Fundy, Nova Scotia. The seasonal cycle of pCO2 is modulated by a diel cycle that is larger in summer than in winter, and a tidal contribution that is primarily M2, with amplitude roughly half that of the diel cycle throughout the year. The interaction between tidal currents and carbonate system variables leads to lateral transport by tidal pumping, which moves alkalinity and DIC out of the bay, opposite to the mean flow in the region, and constitutes a new feature of how this strongly tidal region connects to the larger Gulf of Maine and Northwest Atlantic carbon system. These results suggest that tidal pumping could substantially modulate the coastal ocean's response to global ocean acidification in any region with large tides and spatial variation in biological activity, requiring that high-frequency variability be accounted for in assessments of carbon budgets of coastal regions. [ABSTRACT FROM AUTHOR]