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Ocean biogeochemical modelling

Abstract. 

"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 years to centuries. This Primer explains the process of model construction and the main characteristics, advantages and drawbacks of different model types, from the simplest nutrient–phytoplankton–zooplankton–detritus model to the complex biogeochemical models used in Earth system modelling and climate prediction. [...]".

 

Source: Nature Reviews Methods Primers 
Authors: Katja Fennel et al.
DOI: https://doi.org/10.1038/s43586-022-00154-2 

Read the full article here.


Impact of warming and deoxygenation on the habitat distribution of Pacific halibut in the Northeast Pacific

Abstract. 

"Ocean warming and deoxygenation are already modifying the habitats of many aerobic organisms. Benthic habitat in the Northeast Pacific is sensitive to deoxygenation, as low oxygen concentrations occur naturally in continental shelf bottom waters. Here, we examine the potential impacts of deoxygenation and ocean warming on the habitat distribution of Pacific halibut (Hippoglossus stenolepis), one of the most commercially important groundfish in North America. [...]".

 

Source: Wiley Online Library  
Authors: Ana C. Franco et al.
DOI: https://doi.org/10.1111/fog.12610

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Ventilation changes drive orbital-scale deoxygenation trends in the late Cretaceous ocean

Abstract. 

"Mechanisms that drive cyclicity in marine sediment deposits during hothouse climate periods in response to Earth’s orbit variations remain debated. Orbital cycles fingerprint in the oceanographic records results from the combined effect of terrestrial (e.g. weathering-derived nutrient supply, freshwater discharge) and oceanic (e.g. productivity, oxygenation) processes, whose respective contribution remains to be clarified. [...]".

 

Source: Geophysical Research Letters
Authors: Anta-Clarisse Sarr et al.
DOI: https://doi.org/10.1029/2022GL099830

Read the full article here.


The Fate of Oxygen in the Ocean and Its Sensitivity to Local Changes in Biological Production

Abstract. 

"We investigate the sensitivity of the oxygen content and true oxygen utilization of key low-oxygen regions Ω to pointwise changes in biological production. To understand how the combined water and biogenic particle transport controls the sensitivity patterns and the fate of oxygen in the ocean, we develop new relationships that link the steady-state oxygen content and deficit of Ω to the downstream and upstream oxygen utilization rate (OUR), respectively. We find that the amount of oxygen from Ω that will be lost per unit volume at point r is linked to OUR(r) through the mean oxygen age accumulated in Ω. [...]".

 

Source: Wiley Online Library 
Authors: Mark Holzer
DOI: https://doi.org/10.1029/2022JC018802

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Sensitivity of Global Ocean Deoxygenation to Vertical and Isopycnal Mixing in an Ocean Biogeochemistry Model

Abstract. 

"Large-scale loss of oxygen under global warming is termed “ocean deoxygenation” and is caused by the imbalance between physical supply and biological consumption of oxygen in the ocean interior. Significant progress has been made in the theoretical understanding of ocean deoxygenation; however, many questions remain unresolved. The oxygen change in the tropical thermocline is poorly understood, with diverging projections among different models. Physical oxygen supply is controlled by a suite of processes that transport oxygen-rich surface waters into the interior ocean, which is expected to weaken due to increasing stratification under global warming. [...]".

 

Source: Wiley Online Library

Authors: Taka Ito et al.

DOI: https://doi.org/10.1029/2021GB007151

Read the full article here.


Sensitivity of asymmetric oxygen minimum zones to mixing intensity and stoichiometry in the tropical Pacific using a basin-scale model

Abstract.

"The tropical Pacific Ocean holds the two largest oxygen minimum zones (OMZs) in the world's oceans, showing a prominent hemispheric asymmetry, with a much stronger and broader OMZ north of the Equator. However, many models have difficulties in reproducing the observed asymmetric OMZs in the tropical Pacific. Here, we apply a fully coupled basin-scale model to evaluate the impacts of stoichiometry and the intensity of vertical mixing on the dynamics of OMZs in the tropical Pacific. We first utilize observational data of dissolved oxygen (DO) to calibrate and validate the basin-scale model. Our model experiments demonstrate that enhanced vertical mixing combined with a reduced O:C utilization ratio can significantly improve our model capability of reproducing the asymmetric OMZs. Our study shows that DO concentration is more sensitive to biological processes over 200–400 m but to physical processes below 400 m. [...]".

 

Source: Geoscientific Model Development 

Authors: Kai Wang et al. 

DOI: https://doi.org/10.5194/gmd-15-1017-2022 

Read the full article here.


Biogeochemical feedbacks may amplify ongoing and future ocean deoxygenation: a case study from the Peruvian oxygen minimum zone

Abstract.

"A new box model is employed to simulate the oxygen-dependent cycling of nutrients in the Peruvian oxygen minimum zone (OMZ). Model results and data for the present state of the OMZ indicate that dissolved iron is the limiting nutrient for primary production and is provided by the release of dissolved ferrous iron from shelf and slope sediments. Most of the removal of reactive nitrogen occurs by anaerobic oxidation of ammonium where ammonium is delivered by aerobic organic nitrogen degradation. Model experiments simulating the effects of ocean deoxygenation and warming show that the productivity of the Peruvian OMZ will increase due to the enhanced release of dissolved iron from shelf and slope sediments. A positive feedback loop rooted in the oxygen-dependent benthic iron release amplifies, both, the productivity rise and oxygen decline in ambient bottom waters. [...]". 

 

Source: Biogeochemistry

Authors: Klaus Wallmann et al.

DOI: https://doi.org/10.1007/s10533-022-00908-w 

Read the full article here.


Impacts of Ocean Currents on the South Indian Ocean Extratropical Storm Track through the Relative Wind Effect

Abstract.

"This study examines the role of the relative wind (RW) effect (wind relative to ocean current) in the regional ocean circulation and extratropical storm track in the south Indian Ocean. Comparison of two high-resolution regional coupled model simulations with and without the RW effect reveals that the most conspicuous ocean circulation response is the significant weakening of the overly energetic anticyclonic standing eddy off Port Elizabeth, South Africa, a biased feature ascribed to upstream retroflection of the Agulhas Current (AC).[...]"

 

Source: AMS- American Meteorological Sciety 
Authors: Hyodae Seo et al.
DOI: https://doi.org/10.1175/JCLI-D-21-0142.1

Read the full article here.


Variability-based constraint on ocean primary production models

Abstract.

"Primary production (PP) is fundamental to ocean biogeochemistry, but challengingly variable. Satellite models are unique tools for investigating PP, but are difficult to compare and validate because of the scale separation between in situ and remote measurements, which also are rarely coincident. Here, I argue that satellite estimates should be log-skew-normally distributed, because of this scale separation and because PP measurements are log-normally distributed.[...]"

 

Source: ASLO- Association for the Sciences of the Limnology and Oceanography 
Authors: B. B. Cael et al.
DOI: https://doi.org/10.1002/lol2.10196

Read the full article here.


Investigating the Roles of External Forcing and Ocean Circulation on the Atlantic Multidecadal SST Variability in a Large Ensemble Climate Model Hiera

Abstract.

"This paper attempts to enhance our understanding of the causes of Atlantic Multidecadal Variability, the AMV. Following the literature, we define the AMV as the SST averaged over the North Atlantic basin, linearly detrended and low-pass filtered. There is an ongoing debate about the drivers of the AMV, which include internal variability generated from the ocean or atmosphere (or both), and external radiative forcing. We test the role of these factors in explaining the time history, variance, and spatial pattern of the AMV using[...]"

 

Source: American Meteorological Soceity 
Authors: Lisa N. Murphy et al.
DOI: https://doi.org/10.1175/JCLI-D-20-0167.1

Read the full article here.

 

 


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