Manizza Manfredi

No Thumbnail Available
Last Name
Manizza
First Name
Manfredi
ORCID
0000-0001-6265-8367

Search Results

Now showing 1 - 2 of 2
  • Article
    The processing and impact of dissolved riverine nitrogen in the Arctic Ocean
    (Springer, 2011-06-11) Tank, Suzanne E. ; Manizza, Manfredi ; Holmes, Robert M. ; McClelland, James W. ; Peterson, Bruce J.
    Although the Arctic Ocean is the most riverine-influenced of all of the world’s oceans, the importance of terrigenous nutrients in this environment is poorly understood. This study couples estimates of circumpolar riverine nutrient fluxes from the PARTNERS (Pan-Arctic River Transport of Nutrients, Organic Matter, and Suspended Sediments) Project with a regionally configured version of the MIT general circulation model to develop estimates of the distribution and availability of dissolved riverine N in the Arctic Ocean, assess its importance for primary production, and compare these estimates to potential bacterial production fueled by riverine C. Because riverine dissolved organic nitrogen is remineralized slowly, riverine N is available for uptake well into the open ocean. Despite this, we estimate that even when recycling is considered, riverine N may support 0.5–1.5 Tmol C year−1 of primary production, a small proportion of total Arctic Ocean photosynthesis. Rapid uptake of dissolved inorganic nitrogen coupled with relatively high rates of dissolved organic nitrogen regeneration in N-limited nearshore regions, however, leads to potential localized rates of riverine-supported photosynthesis that represent a substantial proportion of nearshore production.
  • Article
    Modeling transport and fate of riverine dissolved organic carbon in the Arctic Ocean
    (American Geophysical Union, 2009-10-07) Manizza, Manfredi ; Follows, Michael J. ; Dutkiewicz, Stephanie ; McClelland, James W. ; Menemenlis, Dimitris ; Hill, C. N. ; Townsend-Small, Amy ; Peterson, Bruce J.
    The spatial distribution and fate of riverine dissolved organic carbon (DOC) in the Arctic may be significant for the regional carbon cycle but are difficult to fully characterize using the sparse observations alone. Numerical models of the circulation and biogeochemical cycles of the region can help to interpret and extrapolate the data and may ultimately be applied in global change sensitivity studies. Here we develop and explore a regional, three-dimensional model of the Arctic Ocean in which, for the first time, we explicitly represent the sources of riverine DOC with seasonal discharge based on climatological field estimates. Through a suite of numerical experiments, we explore the distribution of DOC-like tracers with realistic riverine sources and a simple linear decay to represent remineralization through microbial degradation. The model reproduces the slope of the DOC-salinity relationship observed in the eastern and western Arctic basins when the DOC tracer lifetime is about 10 years, consistent with published inferences from field data. The new empirical parameterization of riverine DOC and the regional circulation and biogeochemical model provide new tools for application in both regional and global change studies.