Katja Fennel

Katja Fennel
Dalhousie University | Dal · Department of Oceanography

PhD

About

218
Publications
63,184
Reads
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9,431
Citations
Additional affiliations
August 2006 - present
Dalhousie University
Position
  • Professor (Associate)
August 2002 - June 2006
Rutgers, The State University of New Jersey
Position
  • Professor (Assistant)
August 1999 - June 2002
Oregon State University
Position
  • PostDoc Position

Publications

Publications (218)
Article
Full-text available
Nutrient inputs from the Mississippi/Atchafalaya River system into the northern Gulf of Mexico promote high phytoplankton production and lead to high respiration rates. Respiration coupled with water column stratification results in seasonal summer hypoxia in bottom waters on the shelf. In addition to consuming oxygen, respiration produces carbon d...
Article
Full-text available
Rivers deliver large amounts of fresh water, nutrients, and other terrestrially derived materials to the coastal ocean. Where inputs accumulate on the shelf, harmful effects such as hypoxia and eutrophication can result. In contrast, where export to the open ocean is efficient riverine inputs contribute to global biogeochemical budgets. Assessing t...
Article
Full-text available
Aquatic environments experiencing low-oxygen conditions have been described as hypoxic, suboxic, or anoxic zones; oxygen minimum zones; and, in the popular media, the misnomer "dead zones." This review aims to elucidate important aspects underlying oxygen depletion in diverse coastal systems and provides a synthesis of general relationships between...
Article
Full-text available
The circulation in the northwestern North Atlantic Ocean is highly complex, characterized by the confluence of two major western boundary current systems and several shelf currents. Here we present the first comprehensive analysis of transport paths and timescales for the northwestern North Atlantic shelf, which is useful for estimating ventilation...
Article
Full-text available
The occurrence of hypoxia in coastal oceans is a long-standing and growing problem worldwide and is clearly linked to anthropogenic nutrient inputs. While the need for reducing anthropogenic nutrient loads is generally accepted, it is costly and thus requires scientifically sound nutrient-reduction strategies. Issues under debate include the relati...
Article
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The Paris Agreement to limit global warming to well below 2°C requires drastic reductions in greenhouse gas emissions and the balancing of any remaining emissions by carbon dioxide removal (CDR). Due to uncertainties about the potential and durability of many land-based approaches to deliver sufficient CDR, marine CDR options are receiving more and...
Article
Full-text available
A solid understanding of the mechanisms behind the presently observed, rapid warming of the northwest North Atlantic Continental Shelf and their biogeochemical impacts is lacking. We hypothesize that a weakening of the Labrador Current System (LCS), especially the shelfbreak jet along the Scotian Shelf, is contributing to these changes and that the...
Article
Full-text available
This study presents DalROMS-NWA12 v1.0, a coupled ocean circulation–sea ice–biogeochemistry modelling system for the northwest Atlantic Ocean (NWA) in which the circulation and biogeochemistry modules are based on ROMS (Regional Ocean Modeling System). The circulation module is coupled to a sea ice module based on the Community Ice CodE (CICE), and...
Article
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Species Distribution Models (SDMs) are tools for understanding climate-induced habitat changes, yet their outcomes depend heavily on climate model selection. This study compares biomass projections for three key species on the Grand Banks of Newfoundland that are known to be sensitive to warming—snow crab, yellowtail flounder, and Atlantic cod. We...
Article
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Predicting the ocean state in a reliable and interoperable way, while ensuring high-quality products, requires forecasting systems that synergistically combine science-based methodologies with advanced technologies for timely, user-oriented solutions. Achieving this objective necessitates the adoption of best practices when implementing ocean forec...
Article
Marine phytoplankton are fundamental to Earth’s ecology and biogeochemistry. Our understanding of the large-scale dynamics of phytoplankton biomass has greatly benefited from, and is largely based on, satellite ocean color observations from which chlorophyll-a (Chla), a commonly used proxy for carbon biomass, can be estimated. However, ocean color...
Preprint
Full-text available
The ability to model biogeochemical features in the ocean is a key factor in predicting the health of the ocean: it involves the representation of processes and cycles of chemical elements (such as carbon, nutrients and oxygen) and the dynamics of living organisms such as phytoplankton, zooplankton and bacteria. This paper gives an overview of the...
Article
Full-text available
Model uncertainty in simulating the biological carbon pump was quantified and partitioned using 14 models from the Coupled Model Intercomparison Project Phase 6. Uncertainty increases with depth. On the global scale, uncertainty in carbon export dominates above 900 m and uncertainty in transfer efficiency below. Reducing model uncertainty in carbon...
Article
Full-text available
Plain Language Summary The northern Gulf of Mexico is an ecologically and economically vital coastal system facing acidification threats from both climate change and eutrophication (excess nutrients). The first robust multi‐decadal pH reconstruction from 1986 to 2019 revealed recurring summer bottom acidification in the Gulf's oxygen‐depleted “dead...
Article
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Among the documented consequences of anthropogenic global warming are the increased frequency and duration of marine heatwaves in the global ocean. The literature dedicated to Arctic marine heatwaves corroborates those results, but fails to identify the heat sources and sinks. Because of the numerous feedbacks impacting polar regions, understanding...
Article
Full-text available
The coastal ocean contributes to regulating atmospheric greenhouse gas concentrations by taking up carbon dioxide (CO2) and releasing nitrous oxide (N2O) and methane (CH4). In this second phase of the Regional Carbon Cycle Assessment and Processes (RECCAP2), we quantify global coastal ocean fluxes of CO2, N2O and CH4 using an ensemble of global gap...
Article
Full-text available
The global ocean's coastal areas are rapidly experiencing the effects of climate change. These regions are highly dynamic, with relatively small-scale circulation features like shelf break currents playing an important role. Projections can produce widely diverging estimates of future regional circulation structures. Here, we use the northwestern N...
Article
Full-text available
This paper provides an overview and demonstration of emerging float-based methods for quantifying gross primary production (GPP) and net community production (NCP) using Biogeochemical-Argo (BGC-Argo) float data. Recent publications have described GPP methods that are based on the detection of diurnal oscillations in upper-ocean oxygen or particula...
Article
Full-text available
The deliberate increase in ocean alkalinity (referred to as ocean alkalinity enhancement, or OAE) has been proposed as a method for removing CO2 from the atmosphere. Before OAE can be implemented safely, efficiently, and at scale several research questions have to be addressed, including (1) which alkaline feedstocks are best suited and the doses i...
Article
Full-text available
Effective management of data is essential for successful ocean alkalinity enhancement (OAE) research , as it guarantees the long-term preservation, interoperability, discoverability, and accessibility of data. OAE research generates various types of data, such as discrete bottle measurements, autonomous measurements from surface underway and uncrew...
Book
Full-text available
A key objective of the Paris Agreement is to limit global warming to well below 2 °C and pursue efforts to limit such warming to 1.5 °C. All scenarios assessed by the Intergovernmental Panel on Climate Change (IPCC) compatible with this goal require the removal of a substantial amount of carbon dioxide (CO2) on the order of 100–1000 Gt CO2 over the...
Preprint
Full-text available
A solid understanding of the mechanisms behind the presently observed, rapid warming of the northwest North Atlantic Continental Shelf is lacking. We hypothesize that a weakening of the Labrador Current System (LCS), especially the shelfbreak jet along the Scotian Shelf, is contributing to these changes and that the future evolution of the LCS will...
Article
Full-text available
Biogeochemical- (BGC-) Argo aims to deploy and maintain a global array of autonomous profiling floats to monitor ocean biogeochemistry. With over 250,000 profiles collected so far, the BGC-Argo network is rapidly expanding toward the target of a sustained fleet of 1,000 floats. These floats prioritize the measurement of six key properties: oxygen,...
Article
In natural systems, animal‐mediated nutrient transport can be a major driver of primary productivity, but the role of marine megafauna such as cetaceans in mediating the transfer and recycling of nutrients has been overlooked. Here, we developed a spatially resolved, stochastic, nutrient‐transport model for cetaceans in the oceanic Gulf of Mexico u...
Article
Full-text available
The Arctic Ocean is generally undersaturated in CO2 and acts as a net sink of atmospheric CO2. This oceanic uptake is strongly modulated by sea ice, which can prevent air–sea gas exchange and has major impacts on stratification and primary production. Moreover, carbon is stored in sea ice with a ratio of alkalinity to dissolved inorganic carbon tha...
Preprint
Full-text available
The deliberate increase of ocean alkalinity (referred to as Ocean Alkalinity Enhancement or OAE) has been proposed as a method for removing CO2 from the atmosphere. Before OAE can be implemented safely, efficiently, and at scale several research questions have to be addressed including: 1) which alkaline feedstocks are best suited and in what doses...
Preprint
Full-text available
The global ocean’s coastal areas are rapidly experiencing the effects of climate change. These regions are highly dynamic, with relatively small-scale circulation features like shelf-break currents playing an important role. Projections can produce widely diverging estimates of future regional circulation structures. Here, we use the northwest Nort...
Preprint
The coastal ocean contributes to regulating atmospheric greenhouse gas concentrations by taking up carbon dioxide (CO2) and releasing nitrous oxide (N2O) and methane (CH4). Major advances have improved our understanding of the coastal air-sea exchanges of these three gasses since the first phase of the Regional Carbon Cycle Assessment and Processes...
Preprint
Full-text available
This paper provides an overview and demonstration of emerging float-based methods for quantifying gross primary production (GPP) and net community production (NCP) using Biogeochemical-Argo (BGC-Argo) float data. Recent publications have described GPP methods that are based on the detection of diurnal oscillations in upper ocean oxygen or particula...
Article
Full-text available
Plain Language Summary Photosynthesis produces organic particles at the ocean's surface. A fraction of these particles sinks to the deep ocean where they are decomposed into inorganic forms. This process, referred to as the biological carbon pump, leads to the storage of inorganic carbon in the deep ocean for hundreds to thousands of years and infl...
Article
Full-text available
Dinitrogen (N2) fixation was investigated at a pelagic station in the oligotrophic waters of the northern Gulf of Aqaba, Red Sea, between February 2016 and December 2018. In situ 15N2 and 13C incubations were used to evaluate photic and aphotic N2 fixation rates and diazotrophic contribution to water column productivity. N2 fixation rates were typi...
Article
Full-text available
The Changjiang is the largest river in Asia and the main terrestrial source of freshwater and nutrients to the East China Sea (ECS). Nutrient concentrations have long been increasing in the Changjiang, especially after 1960 with urbanization, the development of industrial animal production, and fertilizer application in agriculture, resulting in co...
Article
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The dependence of net primary productivity (NPP), a central metric in ecology and biogeochemistry, on sunlight drives daily cycles in carbon biomass in the ocean's euphotic zone. In this study, we infer NPP from the daily cycle of biomass. These estimates were extracted from bio‐optical measurements collected by an array of robotic profilers distri...
Article
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Ocean biogeochemical models describe the ocean’s circulation, physical properties, biogeochemical properties and their transformations using coupled differential equations. Numerically approximating these equations enables simulation of the dynamic evolution of the ocean state in realistic global or regional spatial domains, across time spans from...
Article
Full-text available
The biological carbon pump exerts a strong control on atmospheric CO2 levels. It includes a range of processes that generate organic carbon in the surface ocean and transport this organic matter from the surface to the deep ocean where it is remineralized and sequestered as inorganic carbon for decades to millennia. While ocean productivity is rela...
Article
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The abundance, distribution, and size of marine species are linked to temperature and nutrient regimes and are profoundly affected by humans through exploitation and climate change. Yet little is known about long-term historical links between ocean environmental changes and resource abundance to provide context for current and potential future tren...
Chapter
Full-text available
The Earth’s climate is strongly affected by the partitioning of carbon between its mobile reservoirs, primarily between the atmosphere and the ocean. The distribution between the reservoirs is being massively perturbed by human activities, primarily due to fossil fuel emissions, with a range of consequences, including ocean warming and acidificatio...
Article
Full-text available
Measuring plankton and associated variables as part of ocean time-series stations has the potential to revolutionize our understanding of ocean biology and ecology and their ties to ocean biogeochemistry. It will open temporal scales (e.g., resolving diel cycles) not typically sampled as a function of depth. In this review we motivate the addition...
Article
Full-text available
Plain Language Summary The ocean is a major sink of anthropogenic CO2, but the magnitude, variability and regional differences of the uptake are not well understood or quantified. Continental shelves, in particular, are regions of intense and variable air‐sea exchange. Previous global studies reported that they follow a latitudinal trend where low‐...
Article
Full-text available
Continental shelves are thought to be affected disproportionately by climate change and are a large contributor to global air–sea carbon dioxide (CO2) fluxes. It is often reported that low-latitude shelves tend to act as net sources of CO2, whereas mid- and high-latitude shelves act as net sinks. Here, we combine a high-resolution regional model wi...
Article
Full-text available
The physical processes driving the genesis of surface- and subsurface-intensified cyclonic and anticyclonic eddies originating from the coastal current system of the Mauritanian Upwelling Region are investigated using a high-resolution (~1.5 km) configuration of GFDL’s Modular Ocean Model. Estimating an energy budget for the boundary current reveal...
Article
Full-text available
The marine nitrogen cycle is a main driver of ocean productivity and affects global climate. Despite decades of study, we still have an incomplete understanding of the role of the marine nitrogen cycle in the Earth system. While marine sediments play a major role in nitrogen cycling in the ocean, magnitudes and mechanisms are largely unconstrained....
Article
Coasts are those regions of the world where the land has an impact on the state of the sea, and that part of the land is in turn affected by the sea. This land–sea interaction may take various forms—geophysical, biological, chemical, sociocultural, and economic. Coasts are conditioned by specific regional conditions. These unique characteristics re...
Article
Full-text available
Given current threats to ocean ecosystem health, there is a growing demand for accurate biogeochemical hindcasts, nowcasts, and predictions. Provision of such products requires data assimilation, i.e., a comprehensive strategy for incorporating observations into biogeochemical models, but current data streams of biogeochemical observations are gene...
Article
Full-text available
A reanalysis is a physically consistent set of optimally merged simulated model states and historical observational data, using data assimilation. High computational costs for modeled processes and assimilation algorithms has led to Earth system specific reanalysis products for the atmosphere, the ocean and the land separately. Recent developments...
Article
Full-text available
Biogeochemistry has an important role to play in many environmental issues of current concern related to global change and air, water, and soil quality. However, reliable predictions and tangible implementation of solutions, offered by biogeochemistry, will need further integration of disciplines. Here, we refocus on how further developing and stre...
Preprint
Full-text available
Given current threats to ocean ecosystem health, there is a growing demand for accurate biogeochemical hindcasts, nowcasts, and predictions. Provision of such products requires data assimilation, i.e., a comprehensive strategy for incorporating observations into biogeochemical models, but current data streams of biogeochemical observations are gene...
Article
Full-text available
Continental shelf regions in the ocean play an important role in the global cycling of carbon and nutrients, but their responses to global change are understudied. Global Earth system models (ESMs), as essential tools for building understanding of ocean biogeochemistry, are used extensively and routinely for projections of future climate states; ho...
Preprint
Full-text available
Continental shelves are thought to be affected disproportionately by climate change and are a large contributor to global air-sea carbon dioxide (CO2) fluxes. It is often reported that low-latitude shelves tend to act as net sources of CO2 whereas mid- and high-latitude shelves act as net sinks. Here, we combine a high-resolution regional model wit...
Article
Full-text available
A three-dimensional physical-biological model of the marginal seas of China was used to analyze interannual and intra-seasonal variations in hypoxic conditions and identify the main processes controlling their generation off the Changjiang (or Yangtze River) estuary. The model was compared against available observations and reproduces the observed...
Preprint
Full-text available
Biogeochemistry has an important role to play in many environmental issues of current concern related to global change and air, water, and soil quality. However, reliable predictions and tangible take-up of solutions offered by biogeochemistry will need further integration of disciplines. Here, we emphasize how further developing ties between biolo...
Article
The need to characterize and track coastal hypoxia has led to the development of geostatistical models based on in situ observations of dissolved oxygen (DO) and mechanistic models based on a representation of biophysical processes. To integrate the benefits of these two distinct modeling approaches, we develop a space-time geostatistical framework...
Article
Full-text available
It is known that surface water eutrophication enhances bottom water ocean acidification via respiration in coastal oceans. However, the role of benthic processes in influencing bottom water acidification has not been sufficiently explored. We examined this issue by analyzing a 10‐year summer carbonate chemistry dataset in bottom water together with...
Article
Full-text available
Oceanic primary production forms the basis of the marine food web and provides a pathway for carbon sequestration. Despite its importance, spatial and temporal variations of primary production are poorly observed, in large part because the traditional measurement techniques are laborious and require the presence of a ship. More efficient methods ar...
Article
Full-text available
Biogeochemical ocean models are useful tools but subject to uncertainties arising from simplifications, inaccurate parameterization of processes, and poorly known model parameters. Parameter optimization is a standard method for addressing the latter but typically cannot constrain all biogeochemical parameters because of insufficient observations....