Bradley Penta

An underwater light attenuation scheme for marine ecosystem models.

Simulation of underwater light is essential for modeling marine ecosystems. A new model of underwater light attenuation is presented and compared with previous models. In situ data collected in Monterey Bay, CA. during September 2006 are used for validation. It is demonstrated that while the new light model is computationally simple and efficient it maintains accuracy and flexibility. When this light model is incorporated into an ecosystem model, the correlation between modeled and observed coastal chlorophyll is improved over an eight-year time period. While the simulation of a deep chlorophyll maximum demonstrates the effect of the new model at depth.

Development of a Hierarchy of Nested Models to Study the California Current System

The Naval Research Laboratory has developed a hierarch of differing resolution data assimilating models in the Pacific Ocean, which includes global models, regional U.S. West Coast models, and high resolution coastal models such as for the Monterey Bay area. The three regional U.S. West Coast models (from 30 degrees N to 49 degrees N), designed to study the California Current System, are based on the Princeton Ocean Model (POM), the Navy Coastal Ocean Model (MCOM), called NCOM-CCS, and the Hybrid Coordinate Ocean Model (HYCOM), respectively. The NCOM-CCS formulation is a parallel version model capable of running reliably on many computer platforms. The model has nesting capabilities and offers the choice of using the sigma or a hybrid (sigma-z) vertical coordinate. The NCOM-CCS model also includes a coupled ecosystem model based on Chai et al., 2002. A variety of scientific issues related to model initialization, forcing, open boundary conditions, and model sign up are discussed. The focus of this paper is on: the sensitivity of the horizontal resolution of atmospheric forcing on the NCOM-CCs model predictive skills; the impact of open boundary conditions and coupling with global models on reproducing major hydrographic conditions in the California Current System; and the analysis of the model mixed layer predictions and data assimilation issues. Qualitative and quantitative comparisons are made between observations and model predictions for October 2000 - December 2001 period.

Impact of submesoscale processes on dynamics of phytoplankton filaments

In Monterey Bay, CA, during northwesterly, upwelling favorable winds, the development of a southward flowing cold jet along the entrance to the Bay is often observed. This dense cold jet separates warm waters of the anticyclonic circulation offshore from the water masses inside the Bay. Interactions between the cold jet and the offshore anticyclonic circulation generate ageostrophic secondary circulation (ASC) cells due to submesoscale processes as, for example, flow interaction with the development of surface frontogenesis and nonlinear Ekman pumping. Based on observations and modeling studies, we evaluate the impact of these submesoscale processes on the formation of chlorophyll a filaments during late spring-earlier summer, and late summer time frames. We show that during the late summer time frame, ASC leads to the development of filaments with high values of chlorophyll a concentration along the edge of the cold jet–in contrast to the earlier summer time, when the ASC mixes phytoplankton much deeper to the area below of the euphotic depth, and chlorophyll a filaments are 3–4 times weaker.

Impact of Satellite Remote Sensing Data on Simulations of Coastal Circulation and Hypoxia on the Louisiana Continental Shelf

We estimated surface salinity flux and solar penetration from satellite data, and performed model simulations to examine the impact of including the satellite estimates on temperature, salinity, and dissolved oxygen distributions on the Louisiana continental shelf (LCS) near the annual hypoxic zone. Rainfall data from the Tropical Rainfall Measurement Mission (TRMM) were used for the salinity flux, and the diffuse attenuation coefficient (Kd) from Moderate Resolution Imaging Spectroradiometer (MODIS) were used for solar penetration. Improvements in the model results in comparison with in situ observations occurred when the two types of satellite data were included. Without inclusion of the satellite-derived surface salinity flux, realistic monthly variability in the model salinity fields was observed, but important inter-annual variability was missed. Without inclusion of the satellite-derived light attenuation, model bottom water temperatures were too high nearshore due to excessive penetration of solar irradiance. In general, these salinity and temperature errors led to model stratification that was too weak, and the model failed to capture observed spatial and temporal variability in water-column vertical stratification. Inclusion of the satellite data improved temperature and salinity predictions and the vertical stratification was strengthened, which improved prediction of bottom-water dissolved oxygen. The model-predicted area of bottom-water hypoxia on the Louisiana shelf, an important management metric, was substantially improved in comparison to observed hypoxic area by including the satellite data.

Attenuation of visible solar radiation in the upper water column: A model based on IOPs

For many oceanic studies, it is changes horizontally with constituents in the water required to know the distribution of visible solar (1, 5), but also changes with depth for any water (6, radiation (EPAR) in the upper water column. 7). One way to reach this is by remote sensing. This To represent the steeper than exponential includes two components: First, EPAR at surface reduction of EpAR with depth, multiple exponential is calculated based on atmosphere properties terms (6, 7) were usually adopted, with an along with the position of the Sun. Second, the attenuation coefficient (or attenuation depth) vertical attenuation of EPAR (KPAR) is derived assigned for each term. These attenuation from products of ocean-color remote sensing. coefficients are kept vertically constant, but Currently, KPAR is estimated based on horizontally vary with Jerlov (5) water types. chlorophyll concentration ((C)) from ocean Recently, simple and explicit models have been color. This kind of approach works well for developed to incorporate satellite-derived waters where all optical properties can be chlorophyll concentrations ((C)) into the adequately described by values of (C), but will description of the attenuation of EpAR. When (C) result in large uncertainties for coastal waters values are provided via satellite observations of where (C) alone cannot accurately describe the ocean color (8, 9), the partition factors and optical properties. In this paper, we present an attenuation coefficients of the terms could be innovative model that describes KPAR as a calculated (4). function of waters inherent optical properties Such kind of approach works for Case-i (lOP).

Occurrence and Spatial Extent of HABs on the West Florida Shelf 2002–Present

Harmful algal blooms (HABs) can lead to severe economic and ecological impacts in coastal areas and can threaten marine life and human health. About three quarters of these toxic blooms are caused by dinoflagellate species. One dinoflagellate species, i.e., Karenia brevis, blooms nearly every year in the Gulf of Mexico, particularly on the West Florida Shelf (WFS), where these blooms cause millions of dollars in socioeconomic damage. In this letter, we use the red band difference (RBD) bloom detection technique for detection of low backscattering phytoplankton blooms, such as K. brevis, and conduct time-series analyses of the spatial extent of these blooms using Moderate Resolution Imaging Spectroradiometer (MODIS) monthly mean data spanning July 2002 (sensor inception) to September 2014. The time-series results show that the RBD successfully detects the documented HABs in the region, illustrating the seasonal and interannual variability, including the extensive blooms of 2005 and 2014.

Are the satellite-observed narrow, streaky chlorophyll filaments locally intensified by the submesoscale processes?

Based on observations and modeling studies we have evaluated the impact of submesoscale processes on the development and intensification of offshore narrow (5-10km wide) phytoplankton filaments during summer time in the Monterey Bay, CA. We have demonstrated that, submesoscale processes (surface frontogenesis and nonlinear Ekman transport) lead to the development of very productive phytoplankton patches along the edges between the cold jet and warm anticyclonic eddy. Our results illustrate that during persistent upwelling favorable winds, submesoscale processes can modulate the development and intensification of offshore narrow (5-10km wide) phytoplankton filaments. These processes can incubate the phytoplankton population offshore (as for example, bioluminescent dinoflagellates during August 2003). These offshore phytoplankton filaments can migrate onshore during relaxed winds following the upwelling, and be an additional source of phytoplankton bloom development in and around Monterey Bay. Therefore, the discussed offshore phytoplankton filaments may be a factor in the Bay ecosystem health, as for example, in the development of such events as harmful algae blooms (HABs). All these emphasize the importance of further observational and modeling studies of these submesoscale processes which impact the development and intensification of offshore phytoplankton filaments.