@article{jarvis_pauer_melendez_wan_lehrter_lowe_simmons_2022, title={<p>Inter-model comparison of simulated Gulf of Mexico hypoxia in response to reduced nutrient loads: Effects of phytoplankton and organic matter parameterization</p>}, volume={151}, ISSN={["1873-6726"]}, DOI={10.1016/j.envsoft.2022.105365}, abstractNote={Complex simulation models are a valuable tool to inform nutrient management decisions aimed at reducing hypoxia in the northern Gulf of Mexico, yet simulated hypoxia response to reduced nutrients varies greatly between models. We compared two biogeochemical models driven by the same hydrodynamics, the Coastal Generalized Ecosystem Model (CGEM) and Gulf of Mexico Dissolved Oxygen Model (GoMDOM), to investigate how they differ in simulating hypoxia and their response to reduced nutrients. Different phytoplankton nutrient kinetics produced 2–3 times more hypoxic area and volume on the western shelf in CGEM compared to GoMDOM. Reductions in hypoxic area were greatest in the western shelf, comprising 72% (∼4,200 km2) of the total shelfwide hypoxia response. The range of hypoxia responses from multiple models suggests a 60% load reduction may result in a 33% reduction in hypoxic area, leaving an annual hypoxic area of ∼9,000 km2 based on the latest 5-yr average (13,928 km2).}, journal={ENVIRONMENTAL MODELLING & SOFTWARE}, author={Jarvis, Brandon M. and Pauer, James J. and Melendez, Wilson and Wan, Yongshan and Lehrter, John C. and Lowe, Lisa L. and Simmons, Cody W.}, year={2022}, month={May} }
 @article{liu_lehrter_dzwonkowski_lowe_coogan_2022, title={Using dissolved oxygen variance to investigate the influence of nonextreme wind events on hypoxia in Mobile Bay, a shallow stratified estuary}, volume={9}, ISSN={["2296-7745"]}, DOI={10.3389/fmars.2022.989017}, abstractNote={Wind forcing plays an important role in determining spatial patterns of estuarine bottom water hypoxia, defined as dissolved oxygen (DO) concentration< 2 mg L-1, by driving coastal circulation patterns and by intensifying mixing of the water column. However, the importance of these wind-driven mixing processes varies with space and time and are dynamically intermingled with biological processes like photosynthesis and respiration making it difficult to tease apart wind impacts on DO dynamics in estuarine systems. Using a high-resolution, three-dimensional numerical model, we studied the effect of a non-extreme southeast wind event on the DO dynamics of Mobile Bay during a hypoxic event in April-May of 2019. A new approach, called ‘vertical dissolved oxygen variance’ (VDOV) was developed to quantitatively separate all the physical and biogeochemical factors in the water column that control the development and dissipation of hypoxia events. The system-wide volume integrated values of VDOV tracked the changes in hypoxic area in the bay and the VDOV tendency term was dominated by contributions from sediment oxygen demand (DO loss via respiration) and vertical dissipation (DO gain via mixing). There was a notable inverse relationship between hypoxia area and wind speed. Further analysis of the local VDOV during a non-extreme southeast wind event showed the wind-induced vertical dissipation was the main factor in eliminating hypoxia from the bay. This enhanced dissipation accounted for both turbulent mixing from wind stress and negative straining of the vertical density gradient from wind induced circulation. The response of DO to the wind forcing prompted the development of two non-dimensional numbers, an advection-diffusion time-scale ratio and a demand-diffusion flux ratio, to better generalize the expected DO dynamics. Overall, this work showed that wind effects are critical for understanding hypoxia variability in a shallow stratified estuary.}, journal={FRONTIERS IN MARINE SCIENCE}, author={Liu, Zhilong and Lehrter, John and Dzwonkowski, Brian and Lowe, Lisa L. and Coogan, Jeff}, year={2022}, month={Nov} }
 @article{jarvis_greene_wan_lehrter_lowe_ko_2021, title={Contiguous Low Oxygen Waters between the Continental Shelf Hypoxia Zone and Nearshore Coastal Waters of Louisiana, USA: Interpreting 30 Years of Profiling Data and Three-Dimensional Ecosystem Modeling}, volume={55}, ISSN={["1520-5851"]}, DOI={10.1021/acs.est.0c05973}, abstractNote={The multidecadal expansion of northern Gulf of Mexico continental shelf hypoxia is a striking example of the adverse effects of anthropogenic nutrient enrichment on coastal oceans. Increased nutrient inputs and widespread shelf hypoxia have resulted in numerous dissolved oxygen (DO) water quality problems in nearshore coastal waters of Louisiana. A large hydrographic dataset compiled from research programs spanning 30 years and the three-dimensional hydrodynamic-biogeochemical model CGEM (Coastal Generalized Ecosystem Model) were integrated to explore the interconnections of low DO waters across the continental shelf to nearshore coastal waters of Louisiana. Cross-shelf vertical profiles showed contiguous low DO bottom waters extending from the shelf to coastal waters nearly every year in the 30+ year time series, which were concurrent with strong cross-shelf pycnoclines. A threshold Brunt-Väisälä frequency of 40 cycles h-1 was critical to maintaining the cross-shelf subpycnocline layers and facilitating the formation of a contiguous low DO water mass. Field observations and model simulations identified periods of wind-driven bottom water upwelling lasting between several days to several weeks, resulting in both physical advection of oxygen-depleted offshore waters to the nearshore and enhanced nearshore stratification. Both the upwelling of low DO bottom waters and in situ respiration were of sufficient temporal and spatial extent to drive DO below Louisiana's DO water quality criteria. Basin-wide nutrient management strategies aimed at reducing nutrient inputs and shelf hypoxia remain essential to improving the nearshore coastal water quality across the northern Gulf of Mexico.}, number={8}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, author={Jarvis, Brandon M. and Greene, Richard M. and Wan, Yongshan and Lehrter, John C. and Lowe, Lisa L. and Ko, Dong S.}, year={2021}, month={Apr}, pages={4709–4719} }
 @article{wang_tian_lowe_kalin_lehrter_2021, title={Deep Learning for Daily Precipitation and Temperature Downscaling}, volume={57}, ISSN={["1944-7973"]}, DOI={10.1029/2020WR029308}, abstractNote={Abstract}, number={4}, journal={WATER RESOURCES RESEARCH}, author={Wang, Fang and Tian, Di and Lowe, Lisa and Kalin, Latif and Lehrter, John}, year={2021}, month={Apr} }
 @article{jarvis_lehrter_lowe_hagy_wan_murrell_ko_penta_gould_2020, title={Modeling Spatiotemporal Patterns of Ecosystem Metabolism and Organic Carbon Dynamics Affecting Hypoxia on the Louisiana Continental Shelf}, volume={125}, ISSN={["2169-9291"]}, DOI={10.1029/2019JC015630}, abstractNote={Abstract}, number={4}, journal={JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS}, author={Jarvis, Brandon M. and Lehrter, John C. and Lowe, Lisa L. and Hagy, James D., III and Wan, Yongshan and Murrell, Michael C. and Ko, Dong S. and Penta, Bradley and Gould, Richard W., Jr.}, year={2020}, month={Apr} }
 @article{pauer_melendez_feist_lehrter_rashleigh_lowe_greene_2020, title={The impact of alternative nutrient kinetics and computational grid size on model predicted primary production and hypoxic area in the northern Gulf of Mexico}, volume={126}, ISSN={["1873-6726"]}, DOI={10.1016/j.envsoft.2020.104661}, abstractNote={Model structure uncertainty is seldom calculated because of the difficulty and time required to perform such analyses. Here we explore how a coastal model using the Monod versus Droop formulations and a 6 km × 6 km versus 2 km × 2 km computational grid size predict primary production and hypoxic area in the Gulf of Mexico. Results from these models were compared to each other and to observations, and sensitivity analyses were performed. The different models fit the observations almost equally well. The 6k-model calculated higher rates of production and settling, and especially a larger hypoxic area, in comparison to the 2k-model. The Monod-based model calculated higher production, especially close to the river delta regions, but smaller summer hypoxic area, than the model using the Droop formulation. The Monod-based model was almost twice as sensitive to changes in nutrient loads in comparison to the Droop model, which can have management implications.}, journal={ENVIRONMENTAL MODELLING & SOFTWARE}, author={Pauer, James J. and Melendez, Wilson and Feist, Timothy J. and Lehrter, John C. and Rashleigh, Brenda and Lowe, Lisa L. and Greene, Richard M.}, year={2020}, month={Apr} }