Accession Number:

ADA470254

Title:

Effects of Nutrients and Physical Forcing on Satellite-Derived Optical Properties Near the Mississippi River Delta

Descriptive Note:

Research paper

Corporate Author:

NAVAL RESEARCH LAB STENNIS SPACE CENTER MS

Report Date:

2007-07-17

Pagination or Media Count:

8.0

Abstract:

We investigated the effects of various chemical and physical forcing mechanisms on optical properties near the Mississippi River delta using a multi-year time series of satellite imagery. Recent cruise data has provided in situ measurements to ground-truth satellite estimates of partitioned absorption phytoplankton, detritus, sediment, and colored dissolved organic matter components. In our time series analyses, we addressed long-term time scales of variability 2002-2004 using monthly composite SeaWiFS imagery and fifteen different physical forcing variables. Correlation and stepwise regression analyses, performed on each image pixel, revealed which forcing mechanisms were most responsible for optical variability. For example, Mississippi River nitrate concentration explained only a portion of the seasonal variability observed in phytoplankton absorption on the Louisiana shelf, and physical factors, such as river discharge and wind speed were as important in determining variability. Such observations have management implications for hypoxia in terms of mandates to decrease nutrient loading to the Mississippi River watershed. Our goal is to develop a robust statistical model for optical prediction. To this end, we applied our stepwise regression model to physical properties for 2005, a year not included in model development. Our model fairly well predicted a ph443 on the Louisiana-Texas shelf, with an average error of 30. In the future, we hope to improve our predictions using seasonally specific models and to analyze shorter time scales days to weeks of variability.

Subject Categories:

  • Biochemistry
  • Photography
  • Optics
  • Unmanned Spacecraft

Distribution Statement:

APPROVED FOR PUBLIC RELEASE