Under Sea Riches

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September 20, 2021 by Helen Hill

story by Helen Hill for MITgcm

Declining conventional availability coupled with burgeoning global demand has triggered renewed interest in deep-sea metal mining. However, there is concern that this new form of extraction could negatively impact seafloor ecology. Recently a team of researchers from Germany, Belgium, and the Netherlands has been using MITgcm in modeling seeking to predict how sediments kicked up by seafloor mining disperse.

With terrestrial reserves of metals such as cobalt, copper, nickel, and manganese increasingly depleted yet a surge in demand to supply a rapidly growing green energy sector forecast, prospectors are once again eyeing the sea-floor as a rich alternative source for these economically valuable materials.

Polymetallic nodules (also termed manganese nodules) are potato-sized mineral concretions of layered iron and manganese hydroxides. A ubiquitous feature of the seafloor throughout the world’s oceans, the largest deposits in terms of abundance and metal concentration occur in the Clarion Clipperton Zone (CCZ) in the Northeast Tropical Pacific. There, at depths of between 4000 and 6000 m, nodules litter the ocean floor with, by some estimates, deposits of over 20 billion tonnes of nodule material. One proposed method of extraction consists in removing the upper ~20cm of the seafloor and separating nodules from sediment in much the same way a commercial harvester would potatoes from soil on land. However, as envisaged, such activity, besides causing localized seafloor disturbance, would also create a wake of suspended sediment the fallout from which, in an environment now known to harbor an abundance and diversity of life, could gravely disrupt local ecology.

Kaveh Purkiani, André Paul and Micahel Schultz from the MARUM Center for Marine Environmental Sciences and Faculty of Geosciences, University of Bremen, Germany; Benjamin Gillard, and Laurenz Thomsen from Jacobs University Bremen, Germany; Matthias Haeckel and Jens Greinert from the GEOMAR Helmholtz Center for Ocean Research, Kiel, Germany; Sabine Haalboom and Henko de Stigter from NIOZ the Royal Netherlands Institute for Sea Research, Department of Ocean Systems, Texel, Netherlands; Martina Hollstein and Annemiek Vink from the Federal Institute for Geosciences and Natural Resources (BGR), Hannover, Germany; and Matthias Baeye from the Royal Belgian Institute of Natural Sciences, Brussels, Belgium have been using MITgcm in their work seeking to reproduce how the sediment plume resulting from sea-floor mining activity disperses. The paper appears in Frontiers in Marine Science.

As noted by the authors “predicting the dispersion of sediment plumes induced by potential deep-sea mining activities is still very limited due to operational limitations on in-situ observations required for a thorough validation and calibration of numerical models”, however, coupling a sediment transport module to a high-resolution regional implementation of MITgcm, the team was able to successfully reproduce the dispersion of the sediment plume induced by a small-scale dredge experiment carried out at a depth of 4200 m in the German license area for the exploration of polymetallic nodules in the CCZ in April 2019.

“By experimenting with different aspects of the plume-system including sediment characteristics and ocean hydrodynamics to obtain the best statistical agreement between the 2019 sensor-based observations and model results we were able to reproduce suspended sediment concentration and redeposition patterns,” says Purkiani the study’s lead author. “Among other determinants, our results suggest that seabed topography and variable sediment release heights above the seafloor are especially important for the low sedimentation pattern in the far-field area. We also found that near-bottom mixing can strongly influence vertical transport of suspended sediment.”

To find out more about this work contact Kaveh

About the Researcher

Kaveh Purkiani is a postdoc working with The Joint Programming Initiative Healthy and Productive Seas and Oceans (JPI Oceans) a European intergovernmental platform for responsible stewardship of the world’s oceans involved in assessing ecological impacts which could arise from commercial mining activities in the deep sea. Kaveh began using MITgcm 5 years ago. When he is not busy with CCZ sediment transport modeling his hobbies are cooking and reading.

Story image: Manganese nodule collected in 1982 from the Pacific. Image width: 8 in – Wikimedia

This Month’s Featured Publication

Other New Publications that appeared this month

Tobias Peter Bauer, Peter Holtermann, Bernd Heinold, Hagen Radtke, Oswald Knoth, and Knut Klingbeil (2021), ICONGETM v1.0 – flexible NUOPC-driven two-way coupling via ESMF exchange grids between the unstructured-grid atmosphere model ICON and the structured-grid coastal ocean model GETM, Geosci. Model Dev., doi: 10.5194/gmd-14-4843-2021

Charles Brunette, L. Bruno Tremblay, and Robert Newton (2021), A new sea ice state dependent parameterization for the free drift of sea ice, The Cryosphere (preprint), doi: 10.5194/tc-2021-249

Ichiro Fukumori, Ou Wang, and Ian Fenty (2021), Causal Mechanisms of Sea-level and Freshwater Content Change in the Beaufort Sea, Journal of Physical Oceanography, doi: 10.1175/JPO-D-21-0069.1

Saeed Hariri (2021), Analysis of mixing structures in the Adriatic Sea using finite-size Lyapunov exponents, Geophysical and Astrophysical Fluid Dynamics, doi: 10.1080/03091929.2021.1962851

Di Jiankai, Ma Chunyong, and Chen Ge (2021), Parallel-Dynamic Interpolation Algorithm of Sea Surface Height for Future 2D Altimetry Mapping of Sea Surface Height, J. Ocean Univ. China (Oceanic and Coastal Sea Research), doi: 10.1007/s11802-021-4664-9

Prabha Kushwaha and Vivek Kumar Pandey (2021), Demonstrating the potential of Regional Ocean Model System in simulating the upper ocean characteristic over Arabian Sea: impact of horizontal resolution, Theoretical and Applied Climatology (in review), doi: 10.21203/rs.3.rs-792515

Lenetsky, Jed E., Understanding Bering Strait Ocean Heat Transport Variability for Seasonal Sea Ice Forecasting in the Chukchi Sea, University of Colorado at Boulder Masters Thesis, ProQuest 28418577

Mishra, A.K., Dubey, A.K. (2021), Sensitivity of convective parameterization schemes in regional climate model: precipitation extremes over India. Theor Appl Climatol, doi: 10.1007/s00704-021-03714-w

Mittal, H.V.R., Langodan, S., Zhan, P. et al. (2021), Hazard assessment of oil spills along the main shipping lane in the Red Sea., Scientific Reports, doi: 10.1038/s41598-021-96572-5

Adele K. Morrison, Darryn W. Waugh, Andrew McC. Hogg, Daniel C. Jones, and Ryan P. Abernathey (2021), Ventilation of the Southern Ocean Pycnocline, Annual Reviews, doi: 10.1146/annurev-marine-010419-011012

Yoshihiro Nakayama et al (2021), Antarctic Slope Current Modulates Ocean Heat Intrusions Towards Totten Glacier, Geophysical Research Letters, doi: 10.1029/2021GL094149

Tyler Pelle et al (2021), Widespread Grounding Line Retreat of Totten Glacier, East Antarctica, Over the 21st Century, Geophysical Research Letters, doi: 10.1029/2021GL093213

Pendleton, S., Condron, A. & Donnelly, J. (2021), The potential of Hudson Valley glacial floods to drive abrupt climate change, Commun Earth Environ, doi: 10.1038/s43247-021-00228-1

Kaveh Purkiani et al (2021), Numerical Simulation of Deep-Sea Sediment Transport Induced by a Dredge Experiment in the Northeastern Pacific Ocean, Frontiers in Marine Science, doi: 10.3389/fmars.2021.719463

Andrew L. Stewart, Xiaoyang Chi, Aviv Solodoch, Andrew McC Hogg (2021), High-frequency fluctuations in Antarctic Bottom Water transport driven by Southern Ocean winds, Geophysical Research Letters, doi: 10.1029/2021GL094569

Lin Yan, Talha Bin Masood, Farhan Rasheed, Ingrid Hotz, Bei Wang (2021), Geometry-Aware Merge Tree Comparisons for Time-Varying Data with Interleaving Distances, arXiv: 2107.14373 [cs.HC]

Do you have news about research using MITgcm? We are looking for contributions to these pages. If you have an interesting MITgcm project (ocean, atmosphere, sea-ice, physics, biology or otherwise) that you want to tell people about, get in touch. To make a post, contact Helen