modeling :: Ocean Carbon & Biogeochemistry

Studying marine ecosystems and biogeochemical cycles in the face of environmental change

Archive for modeling

Quantifying uncertainties in future projections of Chesapeake Bay Hypoxia

Posted by mmaheigan

· Wednesday, December 4th, 2024

Climate change is expected to especially impact coastal zones, worsening deoxygenation in the Chesapeake Bay by reducing oxygen solubility and increasing remineralization rates of organic matter. However, simulated responses of this often fail to account for uncertainties embedded within the application of future climate scenarios.

Recent research published in Biogeosciences and in Scientific Reports sought to tackle multiple sources of uncertainty in future impacts to dissolved oxygen levels by simulating multiple climate scenarios within the Chesapeake Bay region using a coupled hydrodynamic-biogeochemical model. In Hinson et al. (2023), researchers showed that a multitude of climate scenarios projected a slight increase in hypoxia levels due solely to watershed impacts, although the choice of global earth system model, downscaling methodology, and watershed model equally contributed to the relative uncertainty in future hypoxia estimates. In Hinson et al. (2024), researchers also found that the application of climate change scenario forcings itself can have an outsized impact on Chesapeake Bay hypoxia projections. Despite using the same inputs for a set of three experiments (continuous, time slice, and delta), the more commonly applied delta method projected an increase in levels of hypoxia nearly double that of the other experiments. The findings demonstrate the importance of ecosystem model memory, and fundamental limitations of the delta approach in capturing long-term changes to both the watershed and estuary. Together these multiple sources of uncertainty interact in unanticipated ways to alter estimates of future discharge and nutrient loadings to the coastal environment.

Figure 1: Chesapeake Bay hypoxia is sensitive to multiple sources of uncertainty related to the type of climate projection applied and the effect of management actions. Percent contribution to uncertainty from Earth System Model (ESM), downscaling methodology (DSC), and watershed model (WSM) for estimates of (a) freshwater streamflow, (b) organic nitrogen loading, (c) nitrate loading, and (d) change in annual hypoxic volume (ΔAHV). (e) Summary of all experiment results for ΔAHV, expressed as a cumulative distribution function. The Multi-Factor experiment (blue line) used a combination of multiple ESMs, DSCs, and WSMs, the All ESMs experiment (pink line) simulated 20 ESMs while holding the DSC and WSM constant, and the Management experiment (green line) only simulated 5 ESMs with a single DSC and WSM but incorporated reductions in nutrient inputs to the watershed. The vertical dashed black line marks no change in AHV.

Understanding the relative sources of uncertainty and impacts of environmental management actions can improve our confidence in mitigating negative climate impacts on coastal ecosystems. Better quantifying contributions of model uncertainty, that is often unaccounted for in projections, can constrain the range of outcomes and improve confidence in future simulations for environmental managers.

Figure 2: A schematic of differences between the Continuous and Delta experiments. In the Delta experiment a combination of altered distributions in future precipitation and changes to long-term soil nitrogen stores eventually result in increased levels of hypoxia (right panel).

Authors
Kyle E. Hinson (Virginia Institute of Marine Science, William & Mary)
Marjorie A. M. Friedrichs (Virginia Institute of Marine Science, William & Mary)
Raymond G. Najjar (The Pennsylvania State University)
Maria Herrmann (The Pennsylvania State University)
Zihao Bian (Auburn University)
Gopal Bhatt (The Pennsylvania State University, USEPA Chesapeake Bay Program Office)
Pierre St-Laurent (Virginia Institute of Marine Science, William & Mary)
Hanqin Tian (Boston College)
Gary Shenk (USGS Virginia/West Virginia Water Science Center)

Swirling Currents: How Ocean Mesoscale Affects Air-Sea CO2 Exchange

Posted by mmaheigan

· Friday, October 25th, 2024

Due to a sparsity of in‐situ observations and the computational burden of eddy‐resolving global simulations, there has been little analysis on how mesoscale processes (e.g., eddies, meanders—lateral scales of 10s to 100s km) influence air‐sea CO₂ fluxes from a global perspective. Recently, it became computationally feasible to implement global eddy‐resolving [O (10) km] ocean biogeochemical models. Many questions related to the influence of mesoscale motions on CO₂ fluxes remain open, including whether ocean eddies serve as hotspots for CO₂ sink or source in specific dynamic regions.

A recent study in Geophysical Research Letters investigated the contribution of ocean mesoscale variability to air-sea CO₂ fluxes by analyzing the CO₂ flux anomaly within the mesoscale band using a coarse-graining approach in a global eddy-resolving biogeochemical simulation. We found that in eddy-rich mid-latitude regions, ocean mesoscale variability can contribute to over 30% of the total CO₂ flux variability. The cumulative net CO₂ flux associated with mesoscale motions is on the order of 10⁵ tC per year. The global pattern of cumulative mesoscale-related CO₂ flux exhibits significant spatial heterogeneity, with the highest values in western boundary currents, the Antarctic Circumpolar Current, and the equatorial Pacific. The local distribution of cumulative mesoscale-related CO₂ flux displays zonal bands alternate between positive (a net source) and negative (a net sink) due to the meandering nature of ocean mesoscale currents, which is related to local relative vorticity and the background cross-stream pCO₂ gradient.

Figure caption. Mesoscale (<nominal 2 degree) contribution to air‐sea CO₂ flux (F^<2°_CO2)in the model. (a)–(d) Monthly time series of F^<2°_CO2 (black lines) and cumulative F^<2°_CO2 (green/red solid lines) in four locations marked in (e). Dashed lines are the least squares regression of cumulative flux for the period 1982–2000; slopes are indicated in the bottom left; (e) Blue colors imply a CO₂ sink, and red colors represent a source. The figure shows the global distribution of the regressed slopes of cumulative F^<2°_CO2. Units are converted from mol m^-2 per year to kg of CO₂ per year using the atomic mass of CO₂. This figure shows significant spatial heterogeneity of mesoscale-modulated CO₂ flux, showing contributions to both CO₂ sources and sinks across different regions of the ocean, with a magnitude on the order of 10⁵ tC per year.

Authors
Yiming Guo (Yale University; now at Woods Hole Oceanographic Institution)
Mary-Louise Timmermans (Yale University)

Turbulent Mixing: A Dominant Source of Oxygen in the Upper Equatorial Pacific

Posted by mmaheigan

· Tuesday, March 12th, 2024

What balances oxygen removal in the equatorial Pacific? For a long time, oxygen in the eastern and central tropical Pacific was assumed to be mainly supplied by the large-scale advection of remotely ventilated waters via the equatorial current system and meridional circulation. A recent study used an eddy-resolving simulation of a global ocean model to show that turbulent mixing and its regulation by mesoscale eddies play a critical role in balancing oxygen removal (by consumption and upwelling) in the upper thermocline. Deeper in the water column, mean advection by the zonal currents and meridional circulation dominates. This mixing is tightly regulated by tropical instability waves, which intensify the shear between the equatorial currents and enhance the downward turbulent mixing flux of oxygen into the thermocline. Mesoscale phenomena thus play an indirect yet critical role as a local pathway of ventilation in this region. Testing these model-based hypotheses in the real ocean through dedicated field studies and long-term observations is needed to advance our understanding of the observed expansion of the oxygen deficient zones (ODZs) and model their future trajectory in a warmer and more stratified ocean.

Figure: The main processes that set the mean structure of oxygen in the equatorial Pacific are assessed in an eddy resolving simulation of the Community Earth System Model (CESM). Panel a shows the climatological oxygen distribution on the 26.25 isopycnal in CESM. Panels b-e show the contribution of advection by mean circulation and eddies, vertical mixing, and production and consumption. These processes are illustrated in panel f). Figure adapted from Eddebbar et al (2024).

Authors
Yassir A. Eddebbar (Scripps Institution of Oceanography)
Daniel B. Whitt (NASA Ames)
Ariane Verdy, (Scripps Institution of Oceanography)
Matthew R. Mazloff (Scripps Institution of Oceanography)
Aneesh C. Subramanian (CU Boulder)
Matthew C. Long, (National Center for Atmospheric Research)

Ocean iron fertilization may amplify pressures on marine biomass with only a limited climate benefit

Posted by hbenway

· Friday, January 26th, 2024

Amidst a heightened focus on the need for both drastic and immediate emissions reductions and carbon dioxide removal to limit warming to 1.5°C (IPCC, 2022), attention is returning to ocean iron fertilization (OIF) as a means of marine carbon dioxide removal (mCDR). First discussed in the early 1990s by John Martin, the concept posits that fertilization of iron-limited marine phytoplankton would lead to enhanced ocean carbon storage via a stimulation of the ocean’s biological carbon pump. However, we lack knowledge about how OIF might operate in concert with an ocean responding to climate change and what the consequences of altered nutrient consumption patterns might be for marine ecosystems, particularly for fisheries in national exclusive economic zones (EEZs). Tagliabue et al. (2023) addressed this in a recent study using state-of-the-art climate, ocean biogeochemical, and ecosystem models under a high-emissions scenario.

The study’s findings suggested that OIF can contribute at most a few 10s of Pg of mCDR under a high-emissions climate change scenario. This is equivalent to fewer than five years of current emissions and is consistent with earlier modeling assessments. This estimate is based on the modeled representation of carbon and iron cycling and a highly efficient OIF strategy that may be difficult to achieve in practice. Enhanced surface uptake of major nutrients due to OIF also led to a drop in global net primary production, in addition to that due to climate change alone. By then coupling a complex model of upper trophic levels, the projected declines in animal biomass due to climate change were amplified by around a third due to OIF, with the most negative impacts projected to occur in the low latitude EEZs, which are already facing increasing pressures due to climate change.

This work highlights feedbacks within the ocean’s biogeochemical and ecological systems in response to OIF that emerged over large spatial and temporal scales. Associated pressures on marine ecosystems pose major challenges for proposed management and monitoring. Restricting OIF to the highest latitudes of the Southern Ocean might mitigate some of these negative effects, but this only further reduces the minor mCDR benefit, suggesting that OIF may not make a significant contribution.

Authors
A. Tagliabue (Univ. Liverpool)
B. S. Twining (Bigelow Laboratory)
N. Barrier & O. Maury (MARBEC, IRD, IFREMER, CNRS, Université de Montpellier, France)
M. Berger & Laurent Bopp (ENS-LMD, Paris, France)

IPCC. Summary for Policymakers. in Climate Change, 2022: Mitigation of Climate Change. Contribution of Working Group III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (eds. Shukla, P. R. et al.) (Cambridge University Press, 2022).

New evidence suggests that tiny zooplankton might be the biggest problem with carbon cycling in IPCC climate models

Posted by mmaheigan

· Friday, December 1st, 2023

The ocean is the most important sink of anthropogenic emissions and is being considered as a medium to manipulate to draw down even more. Essential in the ocean’s role as a natural carbon-sponge is the net production of organic matter by phytoplankton, some of which sinks and is stored for 100s-1000s of years. Successfully simulating this biological carbon pump is essential for projecting any climate scenario, but it appears that massive uncertainties in the way zooplankton consume phytoplankton are compromising predictions of future climate and our assessment of some strategies to deliberately engineer it.

Figure caption. Grazing pressure is largest source of uncertainty for marine carbon cycling in CMIP6 models a) The global and zonal median winter grazing pressure is shown for all models. b) the coefficient of variation across models (std/mean) is largest for grazing pressure compared 14 major terms in the marine carbon cycle.

A new publication in Communications Earth and Environment explains how our poor understanding of zooplankton biases our best projections of marine carbon sequestration. We compared 11 IPCC climate models and found zooplankton grazing is largest source uncertainty in marine carbon cycling. This uncertainty is over three times larger than that of net primary production and is driven by large differences in different models assumptions about the rate at which zooplankton can consume phytoplankton. Yet, very small changes in zooplankton grazing dynamics (roughly only 5% of the full range used across IPCC models) can increase carbon sequestrations by 2 PgC/yr, which is double the maximum theoretical potential of Southern Ocean Iron Fertilization! Moving forward, to move beyond merely treating zooplankton as a closure term, modelers must look towards novel observational constraints on grazing pressure.

Authors
Tyler Rohr, Anthony J. Richardson, Andrew Lenton, Matthew A. Chamberlain, and Elizabeth H. Shadwick

Unveiling the Past and Future of Ocean Acidification: A Novel Data Product covering 10 Global Surface OA Indicators

Posted by mmaheigan

· Wednesday, August 23rd, 2023

Accurately predicting future ocean acidification (OA) conditions is crucial for advancing research at regional and global scales, and guiding society’s mitigation and adaptation efforts.

As an update to Jiang et al. 2019, this new model-data fusion product:
1. Utilizes an ensemble of 14 distinct Earth System Models from the Coupled Model Intercomparison Project Phase 6 (CMIP6) along with three recent observational ocean carbon data products –>instead of relying on just one model (i.e., the GFDL-ESM2M) this approach reduces potential projection biases in OA indicators.
2. Eliminates model biases using observational data, and model drift with pre-Industrial controls.
3. Covers 10 OA indicators, an expansion from the usual pH, acidity, and buffer capacity.
4. Incorporates the new Shared Socioeconomic Pathways (SSPs).

The use of the most recent observational datasets and a large Earth System Model ensemble is a major step forward in the projection of future surface ocean OA indicators and provides critical information to guide OA mitigation and adaptation efforts.

Figure X. Temporal changes of global average surface ocean OA indicators as reconstructed and projected from 14 CMIP6 Earth System Models after applying adjustments with observational data: (a) fugacity of carbon dioxide (fCO₂), (b) total hydrogen ion content ([H⁺]_total), (c) carbonate ion content ([CO₃^2-]), (d) total dissolved inorganic carbon content (DIC), (e) pH on total scale (pH_T), (f) aragonite saturation state (Ω_arag), (g) total alkalinity content (TA), (h) Revelle Factor (RF), and (i) calcite saturation state (Ω_calc). The asterisk signs on the left-side y-axes show the values in 1750. The numbers along right-side y-axes, i.e., 1-1.9, 1-2.6, 2-4.5, 3-7.0, and 5-8.5, indicate the shared socioeconomic pathway SSP1-1.9, SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5, respectively. These are missing from panel g because the trajectories were more dependent on the model than the SSP.

Authors
Li-Qing Jiang (University Maryland)
John Dunne (NOAA/Geophysical Fluid Dynamics Laboratory)
Brendan R. Carter (University of Washington)
Jerry F. Tjiputra (NORCE Norwegian Research Centre Bjerknes)
Jens Terhaar (Woods Hole Oceanographic Institution)
Jonathan D. Sharp (University of Washington)
Are Olsen (University of Bergen and Bjerknes Centre for Climate Research)
Simone Alin (NOAA/Pacific Marine Environmental Laboratory)
Dorothee C. E. Bakker (University of East Anglia)
Richard A. Feely (NOAA/Pacific Marine Environmental Laboratory)
Jean-Pierre Gattuso (Sorbonne Université)
Patrick Hogan (NOAA/National Centers for Environmental Information)
Tatiana Ilyina (Max Planck Institute for Meteorology)
Nico Lange (GEOMAR Helmholtz Centre for Ocean Research)
Siv K. Lauvset (NORCE Norwegian Research Centre)
Ernie R. Lewis (Brookhaven National Laboratory)
Tomas Lovato (Fondazione Centro Euro-Mediterraneo sui Cambiamenti Climatici)
Julien Palmieri (National Oceanography Centre)
Yeray Santana-Falcón (Université de Toulouse)
Jörg Schwinger (NORCE Norwegian Research Centre)
Roland Séférian (Université de Toulouse)
Gary Strand (US National Center for Atmospheric Research)
Neil Swart (Canadian Centre for Climate Modelling and Analysis)
Toste Tanhua (GEOMAR Helmholtz Centre for Ocean Research)
Hiroyuki Tsujino (JMA Meteorological Research Institute)
Rik Wanninkhof (NOAA/Atlantic Oceanographic Meteorological Laboratory)
Michio Watanabe (Japan Agency for Marine-Earth Science and Technology)
Akitomo Yamamoto (Japan Agency for Marine-Earth Science and Technology)
Tilo Ziehn (CSIRO Oceans and Atmosphere)

Twitter:
@JiangLiqing, @JensTerhaar, @jpGattuso, @j_d_sharp, @AreOlsen, @SimoneAlin, @Dorothee_Bakker, @RFeely, @ilitat, @sivlauvset, @yeraysf, @TosteTanhua,

Severe warming = 15% increase in bacterial respiration: Southern Ocean most impacted

Posted by mmaheigan

· Thursday, March 30th, 2023

The utilization, respiration, and remineralization of organic matter exported from the ocean surface to its depths are key processes in the ocean carbon cycle. Marine heterotrophic Bacteria play a critical role in these activities. However, most three-dimensional (3-D) coupled physical-biogeochemical models do not explicitly include Bacteria as a state variable. Instead, they rely on parameterization to account for the bacteria’s impact on particle flux attenuation.

A recent study examined how bacteria respond to climate change by employing a 3-D coupled ocean biogeochemical model that incorporates explicit bacterial dynamics. The model (CMCC-ESM2) is a part of the Coupled Model Intercomparison Project Phase 6. The authors first evaluated the reliability of century-scale forecasts (2015-2099) for bacterial stocks and rates in the upper 100 m layer against the compiled measurements from the contemporary period (1988-2011). Next the authors analyzed the predicted trends in bacterial stocks and rates under diverse climate scenarios and explored their association with regional differences in temperature and organic carbon stocks. Three crucial findings were revealed. There is a global-scale decrease in bacterial biomass of 5-10%, with a 3-5% increase in the Southern Ocean (Figure 1). In the Southern Ocean, the rise in semi-labile dissolved organic carbon (DOC) leads to an increase in DOC uptake rates of free-living bacteria; in the northern high and low latitudes, the increase in temperature drives the increase in their DOC uptake rates. Importantly, extreme warming could result in a global increase (up to 15%) and even higher in the Southern Ocean (21% increase) in bacterial respiration (Figure 1), potentially leading to a decline in the biological carbon pump.

This analysis is an unprecedented and early effort to understand the climate-induced changes in bacterial dynamics on a global scale in a systematic manner. This study takes us one step closer to comprehending how bacteria influence the functioning of the biological carbon pump and the distribution of organic carbon pools between surface and deep layers, especially their response to climate change.

Figure 1. Global projections of bacterial carbon stocks and rates during the baseline period (1990-2013) and their changes as anomalies under the most-severe climate change scenario (i.e., SSP5-8.5) relative to the baseline period (2076-2099). The stocks and rates during the baseline period (a, b, c, g, h, i) and their changes as anomalies under the most-severe climate change scenario (d, e, f, j, k, l). All variables are depth-integrated in the upper 100 m. Solid-line contours as standard deviation from averaging over 1990-2013. Anomalies are 2076-2099 average values relative to 1990-2013 average values. Global bacterial biomass has decreased by 5-10%, with a 3-5% increase in the Southern Ocean. However, extreme warming may increase bacterial respiration worldwide, thereby reducing the efficiency of the biological carbon pump. This study provides an early attempt to understand the response of bacteria to climate change and their impact on the distribution of organic carbon in the ocean.

Author
Heather Kim, Woods Hole Oceanographic Institution

Towards using historical oxygen observations to reconstruct the air-sea flux of biological oxygen

Posted by mmaheigan

· Tuesday, December 13th, 2022

Dissolved oxygen (O₂) is a central observation in oceanography with a long history of relatively high precision measurements and increasing coverage over the 21^st century. O₂ is a powerful tracer of physical, chemical and biological processes (e.g., photosynthesis and respiration, wave-induced bubbles, mixing, and air-sea diffusion). A commonly used approach to partition the processes controlling the O₂ signal relies on concurrent measurements of argon (an inert gas), which has solubility properties similar to O₂. However, only a limited fraction of O₂ measurements have paired argon measurements.

Figure 1. (a) The newly developed empirical model to parameterize the physical oxygen saturation anomaly (ΔO_2[phy]) in order to separate the biological contribution from total oxygen, and (b-c) regional, inter-annual, and decadal variability of air-sea gas flux of biological oxygen (F[O2]bio as) reconstructed from the historical dissolved oxygen record.

A recent study published in the Journal of Global Biogeochemical Cycles presents semi-analytical algorithms to separate the biological and physical O₂ oxygen signals from O₂ observations. Among the approaches, a machine-learning algorithm using ship-based measurements and historical records of physical parameters from reanalysis products as predictors shows encouraging performance. The researchers leveraged this new algorithm to reconstruct regional, inter-annual, and decadal variability of the air-sea flux of biological oxygen (from historical O₂ records.

The long-term objective of this proof-of-concept effort is to estimate from historical oxygen records and a rapidly growing number of O₂ measurements on autonomous platforms. In regions where vertical and horizontal mixing is weak, the projected approximates net community production, providing an independent constraint on the strength of the biological carbon pump.

Authors:
Yibin Huang (Duke University)
Rachel Eveleth (Oberlin College)
David (Roo) Nicholson (Woods Hole Oceanographic Institution)
Nicolas Cassar (Duke University)

Drivers of recent Chesapeake Bay warming

Posted by mmaheigan

· Friday, August 26th, 2022

Coastal water temperatures have been increasing globally with more frequent marine heat waves threatening marine life and nearshore communities reliant upon these ecosystems. Often, this warming is assumed to be uniform in space and time; however, this is not the case in the Chesapeake Bay, where warming waters play a major role in exacerbating low oxygen levels and indirectly limiting the efficacy of nutrient reduction efforts on land.

New research published in the Journal of the American Water Resources Association combined long-term observations and a hydrodynamic model to quantify the temporal and spatial variability in warming Chesapeake Bay waters, and identify the contributions of different mechanisms driving these historical temperature changes. While winter temperatures have warmed by less than a half a degree over the past 30 years, summer temperatures have warmed by nearly 1.5 °C, with similar increases at the surface and bottom. In cooler months, the atmosphere was the dominant driver of warming throughout the majority of the Bay, but oceanic warming explained more than half of the increased summer temperatures in the southern Bay nearest the Atlantic.

Figure 1: Relative contribution of different factors to warm-month Chesapeake Bay temperature change over the period 1985-2015. Percentages correspond to average main channel contributions for each component.

Warming temperatures have potentially significant implications for the future size of the Chesapeake Bay dead zone, and the marine species directly affected by these low oxygen conditions. Better quantifying warming contributions from the atmosphere, ocean, sea level, and rivers will also help constrain regional temperature projections throughout the estuary. More accurate projections of future Bay temperatures can help coastal managers better understand the potential for invasive species expansion and endemic species loss, impacts to fisheries and aquaculture, and how changes to ecosystem processes may impact coastal communities dependent on a healthy Bay.

Authors:
Kyle E. Hinson (Virginia Institute of Marine Science, William & Mary)
Marjorie A. M. Friedrichs (Virginia Institute of Marine Science, William & Mary)
Pierre St-Laurent (Virginia Institute of Marine Science, William & Mary)
Fei Da (Virginia Institute of Marine Science, William & Mary)
Raymond G. Najjar (The Pennsylvania State University)

Nutrient management improves hypoxia in the Chesapeake Bay despite record-breaking precipitation and warming

Posted by mmaheigan

· Friday, August 26th, 2022

Hypoxia is currently one of the greatest threats to coastal and estuarine ecosystems around the world, and this threat is projected to get worse as waters warm and human populations continue to increase. Over the past 35-years, a massive effort has been underway to decrease hypoxia in the Chesapeake Bay by reducing nutrient input from land. Despite this effort, record-breaking precipitation in 2018-2019 fueled particularly large hypoxic volumes in the Bay, calling into question the efficacy of management actions.

Figure 1. The number of days of additional hypoxia (O2 < 3 mg L^-1) that would have occurred in the Chesapeake Bay if the 35 years of nutrient reductions never occurred, as calculated by differences between a realistic numerical model simulation and one with 1985 nitrogen levels. This management effort has had the greatest impact at the northern and southern edges of the hypoxia in the Bay, where there would have been an additional 60-90 days of O2 < 3 mg L^-1 if nutrient reductions never occurred.

In a recent paper published in Science of the Total Environment, researchers used empirical and numerical modeling to quantify the impact of nutrient management efforts on hypoxia in the Chesapeake Bay. Results suggest that if the nutrient reduction efforts beginning in 1985 had not taken place, hypoxia would have been ~50–120% greater during the average discharge years of 2016–2017 and ~20–50% greater during the wet years of 2018–2019. The management impact was most pronounced in regions of the Bay where the hypoxia season would have been 60-90 days longer if nutrient reductions did not occur (Figure 1).

Although these results suggest that management has reduced hypoxic conditions in the Bay, additional analysis revealed that warming temperatures have already offset 6-34% of this improvement. This highlights the importance of factoring in climate change when setting future management goals.

Figure 2. The number of days of additional hypoxia (O2 < 3 mg L^-1) that would have occurred in the Chesapeake Bay if the 35 years of nutrient reductions never occurred, as calculated by differences between a realistic numerical model simulation and one with 1985 nitrogen levels. This management effort has had the greatest impact at the northern and southern edges of the hypoxia in the Bay, where there would have been an additional 60-90 days of O2 < 3 mg L^-1 if nutrient reductions never occurred.

Authors:
Luke T. Frankel (Virginia Institute of Marine Science, William & Mary)
Marjorie A. M. Friedrichs (Virginia Institute of Marine Science, William & Mary)
Pierre St-Laurent (Virginia Institute of Marine Science, William & Mary)
Aaron J. Bever (Anchor QEA)
Romuald N. Lipcius (Virginia Institute of Marine Science, William & Mary)
Gopal Bhatt (Pennsylvania State University; Chesapeake Bay Program)
Gary W. Shenk (USGS; Chesapeake Bay Program)

Funding for the Ocean Carbon & Biogeochemistry Project Office is provided by the National Science Foundation (NSF) and the National Aeronautics and Space Administration (NASA). The OCB Project Office is housed at the Woods Hole Oceanographic Institution.

Archive for modeling

Filter by Keyword