A Time Series of Sea Surface Nitrate and Nitrate Based New Production in the Global Oceans
Principal Investigator (PI): Joaquim Goes, Lamont Doherty Earth Observatory
The sinking of organic material produced by photosynthesis from the upper euphotic layers into the ocean’s interior represents a potential long-term sink for atmospheric CO2. Its magnitude is regulated primarily by the supply of inorganic nitrogen, primarily nitrate (NO3), to the euphotic layer (Eppley and Peterson, 1979; Lewis et al., 1986, Platt et al., 1989, Flynn and Fasham, 1997). For this reason, understanding the space and time variations of NO3 availability in the euphotic layer is a highly essential aspect of research concerning ocean carbon cycling processes and climate change. Despite its importance, NO3 data obtainable by traditional shipboard techniques fall far short of the spatial and temporal scales required for global climate research. Although NO3 in seawater lacks a distinct electromagnetic signature that can be utilized for its estimation from space, remote sensing data has been suggested as a promising alternative to in situ measurements because NO3 correlates well with seawater temperature. Empirical algorithms for sea surface nitrate (SSN) based on its relationship with sea surface temperature (SST) have been in existence for quite a while, but their application over large temporal and spatial domains has been limited, due to the time and space varying nature of SSN-SST relationships. We have shown however, that it is possible to obtain robust estimates of SSN over local, regional and basin scales at daily, weekly monthly and interannual time scales using remotely sensed Chlorophyll (Chl) and SST (Goes et al., 1999, 2000, 2004). We have also shown the immense potential of this method for mapping NO3-based new production (NnP) in order to measure of carbon export into the world's oceans (Goes et al, 2000, 2004a, b). Here we propose to create two innovative Earth Science Data Records (ESDRs), one SSN and the other NnP, using mature ESDRs of Chl available from NASAs SeaWiFS and MODIS—Aqua and of SST available from National Oceanographic and Atmospheric Administration's National Oceanographic Data Center Long-Term Stewardship and Reanalysis Facility (LTSRF). By aiding in assessments of carbon drawdown into the world's oceans and by providing an innovative means for validating and improving coupled ecosystem models that currently rely on global maps of NO3 generated from multi-year data sets, our proposed ESDRs offer the potential to greatly improve our understanding of the role of the oceans in global carbon cycling, earth system processes and climate change especially in regions and seasons which are inaccessible to traditional shipboard studies. Large-scale data production will be accomplished in collaboration with NASA s Ocean Biology Distributed Active Archive Center (OB.DAAC), which will make the time series evaluation products and related documents available to the public from their web site. The processing system, including routine check for accuracy and quality control, will be designed to accommodate future sensors with ocean-color capabilities. We also plan to disseminate data locally through Columbia University's International Research Institute for Climate and Society, Climate Data Library portal. We envision that our products will be utilized by two communities working on Ocean Carbon Cycling and Global Climate Change studies. This proposal responds to the objectives of the Making Earth System Data Records for Use in Research Environments (MEaSUREs) program that will 1) provide and add mature data records for NASA Earth System research and produce scientific analysis tools and service capabilities; 2) provide a calibrated product with described uncertainties; 3) employ community involvement in ESDR development and apply standards and interfaces for exchange of data and information through a collaboration with OB.DAAC at NASA's Goddard Space Flight Center; and 4) support ongoing data system evolution.
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