[1] The biogeochemistry of continental shelf systems plays an important role in the global elemental cycling of nitrogen and carbon, but remains poorly quantified. We have developed a high-resolution physical-biological model for the U.S. east coast continental shelf and adjacent deep ocean that is nested within a basin-wide North Atlantic circulation model in order to estimate nitrogen fluxes in the shelf area of the Middle Atlantic Bight (MAB). Our biological model is a relatively simple representation of nitrogen cycling processes in the water column and organic matter remineralization at the water-sediment interface that explicitly accounts for sediment denitrification. Climatological and regionally integrated means of nitrate, ammonium, and surface chlorophyll are compared with its model equivalents and were found to agree within 1 standard deviation. We also present regional means of primary production and denitrification, and statistical measures of chlorophyll pattern variability. A nitrogen budget for the MAB shows that the sediment denitrification flux is quantitatively important in determining the availability of fixed nitrogen and shelf primary production (it was found to remove 90% of all the nitrogen entering the MAB). Extrapolation of nitrogen fluxes estimated for the MAB to the North Atlantic basin suggests that shelf denitrification removes 2.3 Â 10 12 mol N annually; this estimate exceeds estimates of N 2 fixation by up to an order of magnitude. Our results emphasize the importance of representing shelf processes in biogeochemical models.

We study the dynamics of the planktonic ecosystem in the coastal upwelling zone within the California Current System using a three-dimensional, eddy-resolving cir-

A new estimate of the heat budget for the North Pacific Ocean is presented in this paper. The seasonal net heat flux and heat storage rates were calculated for the North Pacific Ocean from 1950 to 1990 on a spatial resolution of 5 5. Temperature profiles from the National Ocean Data Center were used to calculate the heat storage rates. Satellite remotely sensed solar irradiance and ship marine weather reports from the Comprehensive Ocean-Atmosphere Data Set were used to calculate the net surface heat flux. Heat storage rates were calculated as the time rate of change of the heat content integrated from the surface down to the isotherm that was 1C less than the coldest locally observed wintertime sea surface temperature, which was defined as the locally observed wintertime ventilation isotherm. The monthly climatology of the 5 5 resolution net heat flux was balanced by the heat storage rate for most regions of the North Pacific. To achieve this balance the net heat flux was calculated using the Liu et al. formulations for latent and sensible heat exchange and a modified version of the Reed cloud correction for solar insolation. The root-mean-square error in the difference between the net heat flux and heat storage rate climatologies was calculated at 40 W m 2. When the individual temperature profiles from the northeastern portion of the basin were normalized to the local 300-m mean temperature, thereby removing some of the potential local changes caused by barotropic variability of water motion, the root-mean-square error in this region was further reduced to 20 W m 2 and the large-scale semiannual periodicity in the difference observed in the subtropics was removed. This normalization process may have removed some of the basin-scale variability in the horizontal heat advection. An estimate of the northward heat transport was calculated by integrating the annual mean net heat flux over the North Pacific. The resulting heat transport values were closer to actual northward heat transport estimates made at 10, 24, 35, and 47N, than previous ocean heat flux estimates. The bias in the data was estimated to be less than 7% by comparing the demeaned seasonal cycle of the net heat flux with that of the heat storage rates. The annual mean net heat flux was then used with the 7% bias and the 20 W m 2 uncertainty to calculate a more constrained error envelope for the annual mean northward heat transport in the North Pacific.

The biodiversity and high productivity of coastal terrestrial and aquatic habitats are the foundation for important benefits to human societies around the world. These globally distributed habitats need frequent and broad systematic assessments, but field surveys only cover a small fraction of these areas. Satellite‐based sensors can repeatedly record the visible and near‐infrared reflectance spectra that contain the absorption, scattering, and fluorescence signatures of functional phytoplankton groups, colored dissolved matter, and particulate matter near the surface ocean, and of biologically structured habitats (floating and emergent vegetation, benthic habitats like coral, seagrass, and algae). These measures can be incorporated into Essential Biodiversity Variables (EBVs), including the distribution, abundance, and traits of groups of species populations, and used to evaluate habitat fragmentation. However, current and planned satellites are not designed to observe the EBVs that change rapidly with extreme tides, salinity, temperatures, storms, pollution, or physical habitat destruction over scales relevant to human activity. Making these observations requires a new generation of satellite sensors able to sample with these combined characteristics: (1) spatial resolution on the order of 30 to 100‐m pixels or smaller; (2) spectral resolution on the order of 5 nm in the visible and 10 nm in the short‐wave infrared spectrum (or at least two or more bands at 1,030, 1,240, 1,630, 2,125, and/or 2,260 nm) for atmospheric correction and aquatic and vegetation assessments; (3) radiometric quality with signal to noise ratios (SNR) above 800 (relative to signal levels typical of the open ocean), 14‐bit digitization, absolute radiometric calibration <2%, relative calibration of 0.2%, polarization sensitivity <1%, high radiometric stability and linearity, and operations designed to minimize sunglint; and (4) temporal resolution of hours to days. We refer to these combined specifications as H4 imaging. Enabling H4 imaging is vital for the conservation and management of global biodiversity and ecosystem services, including food provisioning and water security. An agile satellite in a 3‐d repeat low‐Earth orbit could sample 30‐km swath images of several hundred coastal habitats daily. Nine H4 satellites would provide weekly coverage of global coastal zones. Such satellite constellations are now feasible and are used in various applications.