A high-resolution record of Holocene primary productivity and water-column mixing from the varved sediments of Lake Żabińskie, Poland

Abstract. As with other Western Boundary Currents globally, the East Australian Current (EAC) is highly variable making it a challenge to model and predict. For the EAC region, we combine a high-resolution state-of-the-art numerical ocean model with a variety of traditional and newly available observations using an advanced variational data assimilation scheme. The numerical model is configured using the Regional Ocean Modelling System (ROMS 3.4) and takes boundary forcing from the BlueLink ReANalysis (BRAN3). For the data assimilation, we use an Incremental Strong-Constraint 4-Dimensional Variational (IS4D-Var) scheme, which uses the model dynamics to perturb the initial conditions, atmospheric forcing, and boundary conditions, such that the modelled ocean state better fits and is in balance with the observations. This paper describes the data assimilative model configuration that achieves a significant reduction of the difference between the modelled solution and the observations to give a dynamically consistent “best estimate” of the ocean state over a 2-year period. The reanalysis is shown to represent both assimilated and non-assimilated observations well. It achieves mean spatially averaged root mean squared (rms) residuals with the observations of 7.6 cm for sea surface height (SSH) and 0.4 °C for sea surface temperature (SST) over the assimilation period. The time-mean rms residual for subsurface temperature measured by Argo floats is a maximum of 0.9 °C between water depths of 100 and 300 m and smaller throughout the rest of the water column. Velocities at several offshore and continental shelf moorings are well represented in the reanalysis with complex correlations between 0.8 and 1 for all observations in the upper 500 m. Surface radial velocities from a high-frequency radar array are assimilated and the reanalysis provides surface velocity estimates with complex correlations with observed velocities of 0.8–1 across the radar footprint. A comparison with independent (non-assimilated) shipboard conductivity temperature depth (CTD) cast observations shows a marked improvement in the representation of the subsurface ocean in the reanalysis, with the rms residual in potential density reduced to about half of the residual with the free-running model in the upper eddy-influenced part of the water column. This shows that information is successfully propagated from observed variables to unobserved regions as the assimilation system uses the model dynamics to adjust the model state estimate. This is the first study to generate a reanalysis of the region at such a high resolution, making use of an unprecedented observational data set and using an assimilation method that uses the time-evolving model physics to adjust the model in a dynamically consistent way. As such, the reanalysis potentially represents a marked improvement in our ability to capture important circulation dynamics in the EAC. The reanalysis is being used to study EAC dynamics, observation impact in state-estimation, and as forcing for a variety of downscaling studies.

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Effects of Water Column Mixing and Stratification on Planktonic Primary Production and Dinitrogen Fixation on a Northern Red Sea Coral Reef

Frontiers in Microbiology ◽

10.3389/fmicb.2018.02351 ◽

2018 ◽

Vol 9 ◽

Cited By ~ 3

Author(s):

Arjen Tilstra ◽

Nanne van Hoytema ◽

Ulisse Cardini ◽

Vanessa N. Bednarz ◽

Laura Rix ◽

...

Keyword(s):

Coral Reef ◽

Primary Production ◽

Water Column ◽

Red Sea ◽

Dinitrogen Fixation ◽

Water Column Mixing ◽

Northern Red Sea

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VARDA (VArved sediments DAtabase) – providing and connecting proxy data from annually laminated lake sediments

10.5194/essd-2020-55 ◽

2020 ◽

Author(s):

Arne Ramisch ◽

Alexander Brauser ◽

Mario Dorn ◽

Cecile Blanchet ◽

Brian Brademann ◽

...

Keyword(s):

High Resolution ◽

Lake Sediments ◽

Climate Models ◽

Detailed Comparison ◽

High Temporal Resolution ◽

Proxy Data ◽

Varved Sediments ◽

Proxy Records ◽

Data Compilation ◽

Varved Lake Sediments

Abstract. Varved lake sediments provide long climatic records with high temporal resolution and low associated age uncertainty. Robust and detailed comparison of well-dated and annually laminated sediment records is crucial for reconstructing abrupt and regionally time-transgressive changes as well as validation of spatial and temporal trajectories of past climatic changes. The VARved sediments DAtabase (VARDA) presented here is the first data compilation for varve chronologies and associated palaeoclimatic proxy records. The current version 1.0 allows detailed comparison of published varve records from 95 lakes. VARDA is freely accessible and was created to assess outputs from climate models with high-resolution terrestrial palaeoclimatic proxies. VARDA additionally provides a technical environment that enables to explore the database of varved lake sediments using a connected data-model and can generate a state-of-the-art graphic representation of multi-site comparison. This allows to reassess existing chronologies and tephra events to synchronize and compare even distant varved lake records. Furthermore, the present version of VARDA permits to explore varve thickness data. In this paper, we report in detail on the data mining and compilation strategies for the identification of varved lakes and assimilation of high-resolution chronologies as well as the technical infrastructure of the database. Additional paleoclimate proxy data will be provided in forthcoming updates. The VARDA graph-database and user interface can be accessed online at https://varve.gfz-potsdam.de, all datasets of version 1.0 are available at http://doi.org/10.5880/GFZ.4.3.2019.003 (Ramisch et al., 2019).

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ESTIMACIÓN DE LA PRODUCTIVIDAD PRIMARIA EN DOS BAJOS DE LA PARTE SUR DEL GOLFO DE CALIFORNIA, MÉXICO

CICIMAR Oceánides ◽

10.37543/oceanides.v23i1-2.43 ◽

2008 ◽

Vol 23 (1-2) ◽

pp. 39

Author(s):

G. Verdugo-Díaz ◽

R. Cervantes Duarte ◽

M. O. Albáñez-Lucero

Keyword(s):

Surface Temperature ◽

Water Column ◽

Primary Productivity ◽

Gulf Of California ◽

Inorganic Nutrients ◽

Water Transparency ◽

Vertical Profiles ◽

Subsurface Maximum ◽

Natural Fluorescence ◽

Productivity Estimation

Primary productivity estimation in two seamounts in the southern Gulf of California, México Vertical profiles of temperature and natural fluorescence from 100 m deep were made during February 2005. Water transparency was measured using Secchi’s disc, as well samples of superficial water and at maximum of fluorescence deep were collected to analyze inorganic nutrients. In “El Bajo Espiritu Santo” temperature (20 °C at surface) diminished gradually with depth, without significant stratification.Primary productivity shows superficial values close to 6 mg C m-3 h-1, recahing undetectable values at 20 m of depth. In “El Bajo Gorda” surface temperature reached 22 °C and the water column shows a thermocline between 35 m and 45 m of depth. The profiles of primary productivity presented a subsurface maximum (approximately 2 mg C m-3 h-1) associated with the thermocline.

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High-resolution underwater laser spectrometer sensing provides new insights into methane distribution at an Arctic seepage site

Ocean Science ◽

10.5194/os-15-1055-2019 ◽

2019 ◽

Vol 15 (4) ◽

pp. 1055-1069 ◽

Cited By ~ 5

Author(s):

Pär Jansson ◽

Jack Triest ◽

Roberto Grilli ◽

Bénédicte Ferré ◽

Anna Silyakova ◽

...

Keyword(s):

High Resolution ◽

Water Column ◽

Numerical Models ◽

Fast Response ◽

Laser Spectrometer ◽

Current Standard ◽

Discrete Sampling ◽

Mixing Ratios ◽

Technological Advances ◽

Ocean Measurements

Abstract. Methane (CH4) in marine sediments has the potential to contribute to changes in the ocean and climate system. Physical and biochemical processes that are difficult to quantify with current standard methods such as acoustic surveys and discrete sampling govern the distribution of dissolved CH4 in oceans and lakes. Detailed observations of aquatic CH4 concentrations are required for a better understanding of CH4 dynamics in the water column, how it can affect lake and ocean acidification, the chemosynthetic ecosystem, and mixing ratios of atmospheric climate gases. Here we present pioneering high-resolution in situ measurements of dissolved CH4 throughout the water column over a 400 m deep CH4 seepage area at the continental slope west of Svalbard. A new fast-response underwater membrane-inlet laser spectrometer sensor demonstrates technological advances and breakthroughs for ocean measurements. We reveal decametre-scale variations in dissolved CH4 concentrations over the CH4 seepage zone. Previous studies could not resolve such heterogeneity in the area, assumed a smoother distribution, and therefore lacked both details on and insights into ongoing processes. We show good repeatability of the instrument measurements, which are also in agreement with discrete sampling. New numerical models, based on acoustically evidenced free gas emissions from the seafloor, support the observed heterogeneity and CH4 inventory. We identified sources of CH4, undetectable with echo sounder, and rapid diffusion of dissolved CH4 away from the sources. Results from the continuous ocean laser-spectrometer measurements, supported by modelling, improve our understanding of CH4 fluxes and related physical processes over Arctic CH4 degassing regions.

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Seabed Resuspension in the Chesapeake Bay: Implications for Biogeochemical Cycling and Hypoxia

Estuaries and Coasts ◽

10.1007/s12237-020-00763-8 ◽

2020 ◽

Vol 44 (1) ◽

pp. 103-122

Author(s):

Julia M. Moriarty ◽

Marjorie A. M. Friedrichs ◽

Courtney K. Harris

Keyword(s):

Organic Matter ◽

Chesapeake Bay ◽

Water Column ◽

Primary Productivity ◽

Environmental Changes ◽

Light Attenuation ◽

Sediment Resuspension ◽

Nitrogen Dynamics ◽

Biogeochemical Model ◽

Order Of Magnitude

AbstractSediment processes, including resuspension and transport, affect water quality in estuaries by altering light attenuation, primary productivity, and organic matter remineralization, which then influence oxygen and nitrogen dynamics. The relative importance of these processes on oxygen and nitrogen dynamics varies in space and time due to multiple factors and is difficult to measure, however, motivating a modeling approach to quantify how sediment resuspension and transport affect estuarine biogeochemistry. Results from a coupled hydrodynamic–sediment transport–biogeochemical model of the Chesapeake Bay for the summers of 2002 and 2003 showed that resuspension increased light attenuation, especially in the northernmost portion of the Bay, shifting primary production downstream. Resuspension also increased remineralization in the central Bay, which experienced larger organic matter concentrations due to the downstream shift in primary productivity and estuarine circulation. As a result, oxygen decreased and ammonium increased throughout the Bay in the bottom portion of the water column, due to reduced photosynthesis in the northernmost portion of the Bay and increased remineralization in the central Bay. Averaged over the channel, resuspension decreased oxygen by ~ 25% and increased ammonium by ~ 50% for the bottom water column. Changes due to resuspension were of the same order of magnitude as, and generally exceeded, short-term variations within individual summers, as well as interannual variability between 2002 and 2003, which were wet and dry years, respectively. Our results quantify the degree to which sediment resuspension and transport affect biogeochemistry, and provide insight into how coastal systems may respond to management efforts and environmental changes.

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Primary Productivity of Southern Indian Lake before, during, and after Impoundment and Churchill River Diversion

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f84-072 ◽

1984 ◽

Vol 41 (4) ◽

pp. 591-604 ◽

Cited By ~ 48

Author(s):

R. E. Hecky ◽

S. J. Guildford

Keyword(s):

Light Intensity ◽

Primary Production ◽

Water Column ◽

Primary Productivity ◽

Phosphorus Deficiency ◽

Light Environment ◽

Phytoplankton Production ◽

Light Penetration ◽

The Mean ◽

Chlorophyll Concentrations

The primary productivity of seven regions of Southern Indian Lake and neighboring Wood Lake was measured during open-water seasons from 1974 to 1978. The lake had regional differences in chlorophyll concentrations and daily rates of integral primary production in 1974 and 1975 prior to impoundment of the lake. Regions receiving Churchill River flow tended to have higher chlorophyll concentrations and production rates than those regions marginal to the flow. Impoundment of the lake resulted in higher efficiencies of primary production in all regions, as indicated by higher light-saturated rates of carbon uptake per unit chlorophyll and by higher initial slopes of the hyperbolic light response relation of the phytoplankton. Many large basins of the lake had light penetration reduced by high concentrations of suspended sediment from eroding shorelines, while other areas had relatively unchanged light penetration. The increased efficiency of carbon fixation per unit chlorophyll resulted in higher rates of integral production in those regions where light penetration was not greatly affected. Daily rates of integral primary production in lake regions where light penetration had decreased markedly were not significantly different after impoundment because efficiencies of light utilization were higher. Comparison of the mean water column light intensities for those turbid regions with the values of Ik (light intensity at the onset of light saturation) for phytoplankton indicated that these turbid regions are now light deficient on average. Phosphorus deficiency, as indicated by alkaline phosphatase activity per unit ATP, which was present before impoundment, has been eliminated as the mean water column light intensity declined below 5 mEinsteins∙m−2∙min−1. The light environment of a new reservoir can be a significant determinant of integral production, and predicting the consequences of impoundment on phytoplankton production requires accurate prediction of the light environment.

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2000 years of marine primary productivity in the Eastern Tropical North Pacific

10.5194/egusphere-egu2020-903 ◽

2020 ◽

Author(s):

Christina Treinen-Crespo ◽

Jose Carriquiry ◽

Julio Villaescusa ◽

Elisabet Repiso-Terrones

Keyword(s):

High Resolution ◽

Climate Variability ◽

Primary Productivity ◽

North Pacific ◽

Biogenic Silica ◽

Change Scenario ◽

The Past ◽

Past 2000 Years ◽

Increasing Trend ◽

Marine Primary Productivity

<p>Changes in marine primary productivity (MPP) over the 21st century are expected to occur under the prevailing climate change scenario. For better understanding of past climate variability, we reconstructed MPP at high resolution (~1-2 years) for the past 2000 years analyzing biogenic silica and total organic carbon (TOC %) on a sediment core collected from Soledad Basin (25&#176;N, 112&#176;W), Baja&#160; California, Mexico. Located in the Eastern Tropical North Pacific, this suboxic basin is ideal for palaeoceanographic reconstructions due to its high sedimentation rate (2 mm/year), which allow us to reconstruct past changes in the ocean and climate at high resolution. Our results show an increasing trend in the variability of MPP for the past 2000 years: biogenic silica content does not show a well-defined trend, but rather it is dominated by strong multidecadal and prominent centennial-scale cycles while TOC (%) shows a slight increasing trend towards the present, starting at least 2000 years ago. Spectral analysis confirms the presence of multidecadal to centennial cycles. These results will be discussed in the context of the Anthropocene and natural climate variability.</p>

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