Pub Date : 2024-08-05DOI: 10.1038/s41561-024-01497-z
Alexandre Normandeau, Jordan B. R. Eamer, Robert G. Way, Emma J. Harrison, Frédéric Cyr, Christopher K. Algar, Jennifer L. Eamer, Haley D. Geizer, Jessica Haddock, Barret L. Kurylyk, Nicolas Van Nieuwenhove, Liz Pijogge, Geneviève Philibert, Katleen Robert, Michelle Saunders, Joseph Tamborski, Audrey Limoges
The distribution and state of subsea permafrost is largely unknown. Present maps, which rely heavily on model results, suggest that subsea permafrost is confined to the Beaufort, Siberian and Laptev seas. Here we show that discontinuous subsea permafrost exists along the Labrador coast (56 °N) under the influence of the Labrador Coastal Current. High-resolution bathymetric data reveal the presence of subsea thermokarst environments on the coastal seabed of Nain, Nunatsiavut, where an ice-rich sediment sample was recovered in July 2022 at a water depth of 27 m. Porewater analysis indicates that ground ice can persist in the sediments due to freshened submarine groundwater seepage that freezes at higher temperatures (0 °C) than seawater (−1.8 °C). The formation and preservation of subsea permafrost landforms is due to cold waters of the Labrador Coastal Current entering the coastal areas and remaining less than 0 °C for most of the year. Therefore, evidence of subsea permafrost landforms in coastal Labrador and the distribution of cold bottom water in the Northern Hemisphere suggests that subsea permafrost is likely to be preserved elsewhere in subarctic regions, especially where freshened submarine groundwater seepage elevates the freezing temperature. This highlights the potential underestimation of subsea permafrost in the world’s coastal oceans. Observations from the Labrador Coast indicate the presence of subsea permafrost landforms outside of the Arctic, suggesting a potential underestimation of subsea permafrost in the world’s oceans.
{"title":"Evidence for subsea permafrost in subarctic Canada linked to submarine groundwater discharge","authors":"Alexandre Normandeau, Jordan B. R. Eamer, Robert G. Way, Emma J. Harrison, Frédéric Cyr, Christopher K. Algar, Jennifer L. Eamer, Haley D. Geizer, Jessica Haddock, Barret L. Kurylyk, Nicolas Van Nieuwenhove, Liz Pijogge, Geneviève Philibert, Katleen Robert, Michelle Saunders, Joseph Tamborski, Audrey Limoges","doi":"10.1038/s41561-024-01497-z","DOIUrl":"10.1038/s41561-024-01497-z","url":null,"abstract":"The distribution and state of subsea permafrost is largely unknown. Present maps, which rely heavily on model results, suggest that subsea permafrost is confined to the Beaufort, Siberian and Laptev seas. Here we show that discontinuous subsea permafrost exists along the Labrador coast (56 °N) under the influence of the Labrador Coastal Current. High-resolution bathymetric data reveal the presence of subsea thermokarst environments on the coastal seabed of Nain, Nunatsiavut, where an ice-rich sediment sample was recovered in July 2022 at a water depth of 27 m. Porewater analysis indicates that ground ice can persist in the sediments due to freshened submarine groundwater seepage that freezes at higher temperatures (0 °C) than seawater (−1.8 °C). The formation and preservation of subsea permafrost landforms is due to cold waters of the Labrador Coastal Current entering the coastal areas and remaining less than 0 °C for most of the year. Therefore, evidence of subsea permafrost landforms in coastal Labrador and the distribution of cold bottom water in the Northern Hemisphere suggests that subsea permafrost is likely to be preserved elsewhere in subarctic regions, especially where freshened submarine groundwater seepage elevates the freezing temperature. This highlights the potential underestimation of subsea permafrost in the world’s coastal oceans. Observations from the Labrador Coast indicate the presence of subsea permafrost landforms outside of the Arctic, suggesting a potential underestimation of subsea permafrost in the world’s oceans.","PeriodicalId":19053,"journal":{"name":"Nature Geoscience","volume":"17 10","pages":"1022-1030"},"PeriodicalIF":15.7,"publicationDate":"2024-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141895477","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-02DOI: 10.1038/s41561-024-01485-3
Fabio A. Capitanio, Madeleine Kerr, Dave R. Stegman, Suzanne E. Smrekar
The Ishtar Terra highlands on Venus consist of Lakshmi Planum, an Australia-sized crustal plateau with an average elevation of ~4 km that is comparable to that of the Tibetan Plateau, surrounded by elongated mountain belts with elevations of around 10 km, taller than the Himalayas. The region is floored by thick crust that is comparable to that of cratons on Earth. On Earth, plateaus and mountain belts result from the collision of tectonic plates. However, the origin of Ishtar Terra remains enigmatic because Venus lacks Earth-like plate tectonics. Here we use three-dimensional thermo-chemo-mechanical computational simulations of Venus-like mantle convection to show how magmatism and tectonics emerge from mantle dynamics. The simulations show that a lithosphere weakened as a result of high initial hydration or high surface temperatures enhances convective thinning and decompression melting, favouring the emplacement of a thick magmatic crust on top of a deep residual depleted mantle. The stiffer residual root deflects mantle flow outwards, leading to the formation of fold belts around the buoyant lithosphere that are consequently uplifted into a plateau and preserved from further deformation. The modelled topography, crustal thicknesses and gravity is consistent with observational constraints of Ishtar Terra. Our findings suggest that plateau formation on Venus may operate similarly to craton formation on the hot early Earth, before the onset of plate tectonics. Venusian highland terrains such as Ishtar Terra formed from melting beneath thinned lithosphere that created a stiff mantle root in a mechanism akin to craton formation on the early Earth, according to three-dimensional computational simulations.
{"title":"Ishtar Terra highlands on Venus raised by craton-like formation mechanisms","authors":"Fabio A. Capitanio, Madeleine Kerr, Dave R. Stegman, Suzanne E. Smrekar","doi":"10.1038/s41561-024-01485-3","DOIUrl":"10.1038/s41561-024-01485-3","url":null,"abstract":"The Ishtar Terra highlands on Venus consist of Lakshmi Planum, an Australia-sized crustal plateau with an average elevation of ~4 km that is comparable to that of the Tibetan Plateau, surrounded by elongated mountain belts with elevations of around 10 km, taller than the Himalayas. The region is floored by thick crust that is comparable to that of cratons on Earth. On Earth, plateaus and mountain belts result from the collision of tectonic plates. However, the origin of Ishtar Terra remains enigmatic because Venus lacks Earth-like plate tectonics. Here we use three-dimensional thermo-chemo-mechanical computational simulations of Venus-like mantle convection to show how magmatism and tectonics emerge from mantle dynamics. The simulations show that a lithosphere weakened as a result of high initial hydration or high surface temperatures enhances convective thinning and decompression melting, favouring the emplacement of a thick magmatic crust on top of a deep residual depleted mantle. The stiffer residual root deflects mantle flow outwards, leading to the formation of fold belts around the buoyant lithosphere that are consequently uplifted into a plateau and preserved from further deformation. The modelled topography, crustal thicknesses and gravity is consistent with observational constraints of Ishtar Terra. Our findings suggest that plateau formation on Venus may operate similarly to craton formation on the hot early Earth, before the onset of plate tectonics. Venusian highland terrains such as Ishtar Terra formed from melting beneath thinned lithosphere that created a stiff mantle root in a mechanism akin to craton formation on the early Earth, according to three-dimensional computational simulations.","PeriodicalId":19053,"journal":{"name":"Nature Geoscience","volume":"17 8","pages":"740-746"},"PeriodicalIF":15.7,"publicationDate":"2024-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141877671","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-29DOI: 10.1038/s41561-024-01516-z
Stephanie A. Henson, Charlotte Laufkötter, Shirley Leung, Sarah L. C. Giering, Hilary I. Palevsky, Emma L. Cavan
{"title":"Author Correction: Uncertain response of ocean biological carbon export in a changing world","authors":"Stephanie A. Henson, Charlotte Laufkötter, Shirley Leung, Sarah L. C. Giering, Hilary I. Palevsky, Emma L. Cavan","doi":"10.1038/s41561-024-01516-z","DOIUrl":"10.1038/s41561-024-01516-z","url":null,"abstract":"","PeriodicalId":19053,"journal":{"name":"Nature Geoscience","volume":"17 9","pages":"944-944"},"PeriodicalIF":15.7,"publicationDate":"2024-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s41561-024-01516-z.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142165799","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-29DOI: 10.1038/s41561-024-01503-4
Jon Mound, Chris Davies, Sebastian Rost, Jon Aurnou
{"title":"Author Correction: Regional stratification at the top of Earth’s core due to core–mantle boundary heat flux variations","authors":"Jon Mound, Chris Davies, Sebastian Rost, Jon Aurnou","doi":"10.1038/s41561-024-01503-4","DOIUrl":"10.1038/s41561-024-01503-4","url":null,"abstract":"","PeriodicalId":19053,"journal":{"name":"Nature Geoscience","volume":"17 8","pages":"814-815"},"PeriodicalIF":15.7,"publicationDate":"2024-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s41561-024-01503-4.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141790958","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-25DOI: 10.1038/s41561-024-01494-2
Lewis P. Bailey, Michael A. Clare, James E. Hunt, Ian A. Kane, Elda Miramontes, Marco Fonnesu, Ricardo Argiolas, Giuseppe Malgesini, Regis Wallerand
Deep-sea transport of sediment and associated matter, such as organic carbon, nutrients and pollutants, is controlled by near-bed currents. On the continental slope, these currents include episodic down-slope gravity-driven turbidity currents and more sustained thermohaline-driven along-slope contour currents. Recent advancements in deep-sea monitoring have catalysed a step change in our understanding of turbidity currents and contour currents individually. However, these processes rarely operate in isolation and the near-bed current regime is still to be quantified in a mixed system. Such measurements are crucial for understanding deep-sea particulate transport, calibrating numerical models and reconstructing palaeoflow. Here we use 4 years of observations from 34 instrument moorings in a mixed system offshore of Mozambique to show that near-bed currents are highly dynamic. We observe spatial variability in velocity over tidal and seasonal timescales, including reversals in current direction, and a strong steering and funnelling influence by local seabed morphology. The observed near-bed currents are capable of mobilizing and distributing sediments across the seabed, therefore complicating deep-sea particulate transport and reconstruction of palaeoceanographic conditions. Mooring observations suggest that deep-sea currents exhibit substantial variability over tidal and seasonal timescales, driving a complex pattern of sediment transport.
{"title":"Highly variable deep-sea currents over tidal and seasonal timescales","authors":"Lewis P. Bailey, Michael A. Clare, James E. Hunt, Ian A. Kane, Elda Miramontes, Marco Fonnesu, Ricardo Argiolas, Giuseppe Malgesini, Regis Wallerand","doi":"10.1038/s41561-024-01494-2","DOIUrl":"10.1038/s41561-024-01494-2","url":null,"abstract":"Deep-sea transport of sediment and associated matter, such as organic carbon, nutrients and pollutants, is controlled by near-bed currents. On the continental slope, these currents include episodic down-slope gravity-driven turbidity currents and more sustained thermohaline-driven along-slope contour currents. Recent advancements in deep-sea monitoring have catalysed a step change in our understanding of turbidity currents and contour currents individually. However, these processes rarely operate in isolation and the near-bed current regime is still to be quantified in a mixed system. Such measurements are crucial for understanding deep-sea particulate transport, calibrating numerical models and reconstructing palaeoflow. Here we use 4 years of observations from 34 instrument moorings in a mixed system offshore of Mozambique to show that near-bed currents are highly dynamic. We observe spatial variability in velocity over tidal and seasonal timescales, including reversals in current direction, and a strong steering and funnelling influence by local seabed morphology. The observed near-bed currents are capable of mobilizing and distributing sediments across the seabed, therefore complicating deep-sea particulate transport and reconstruction of palaeoceanographic conditions. Mooring observations suggest that deep-sea currents exhibit substantial variability over tidal and seasonal timescales, driving a complex pattern of sediment transport.","PeriodicalId":19053,"journal":{"name":"Nature Geoscience","volume":"17 8","pages":"787-794"},"PeriodicalIF":15.7,"publicationDate":"2024-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s41561-024-01494-2.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141764076","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-25DOI: 10.1038/s41561-024-01498-y
Suqin Q. Duan, Fiaz Ahmed, J. David Neelin
Moist heatwaves in the tropics and subtropics pose substantial risks to society, yet the dynamics governing their intensity are not fully understood. The onset of deep convection arising from hot, moist near-surface air has been thought to limit the magnitude of moist heatwaves. Here we use reanalysis data, output from the Coupled Model Intercomparison Project Phase 6 and model entrainment perturbation experiments to show that entrainment of unsaturated air in the lower-free troposphere (roughly 1–3 km above the surface) limits deep convection, thereby allowing much higher near-surface moist heat. Regions with large-scale subsidence and a dry lower-free troposphere, such as coastal areas adjacent to hot and arid land, are thus particularly susceptible to moist heatwaves. Even in convective regions such as the northern Indian Plain, Southeast Asia and interior South America, the lower-free tropospheric dryness strongly affects the maximum surface wet-bulb temperature. As the climate warms, the dryness (relative to saturation) of the lower-free tropospheric air increases and this allows for a larger increase of extreme moist heat, further elevating the likelihood of moist heatwaves. Climate model simulations and reanalysis data suggest that inhibition of atmospheric convection by dry air intensifies moist heatwaves, and this process may further increase moist heatwaves under climate warming.
{"title":"Moist heatwaves intensified by entrainment of dry air that limits deep convection","authors":"Suqin Q. Duan, Fiaz Ahmed, J. David Neelin","doi":"10.1038/s41561-024-01498-y","DOIUrl":"10.1038/s41561-024-01498-y","url":null,"abstract":"Moist heatwaves in the tropics and subtropics pose substantial risks to society, yet the dynamics governing their intensity are not fully understood. The onset of deep convection arising from hot, moist near-surface air has been thought to limit the magnitude of moist heatwaves. Here we use reanalysis data, output from the Coupled Model Intercomparison Project Phase 6 and model entrainment perturbation experiments to show that entrainment of unsaturated air in the lower-free troposphere (roughly 1–3 km above the surface) limits deep convection, thereby allowing much higher near-surface moist heat. Regions with large-scale subsidence and a dry lower-free troposphere, such as coastal areas adjacent to hot and arid land, are thus particularly susceptible to moist heatwaves. Even in convective regions such as the northern Indian Plain, Southeast Asia and interior South America, the lower-free tropospheric dryness strongly affects the maximum surface wet-bulb temperature. As the climate warms, the dryness (relative to saturation) of the lower-free tropospheric air increases and this allows for a larger increase of extreme moist heat, further elevating the likelihood of moist heatwaves. Climate model simulations and reanalysis data suggest that inhibition of atmospheric convection by dry air intensifies moist heatwaves, and this process may further increase moist heatwaves under climate warming.","PeriodicalId":19053,"journal":{"name":"Nature Geoscience","volume":"17 9","pages":"837-844"},"PeriodicalIF":15.7,"publicationDate":"2024-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141764075","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-25DOI: 10.1038/s41561-024-01515-0
Russell Deitrick, Colin Goldblatt
{"title":"Author Correction: Past Earth warmed by tidal resonance-induced organization of clouds under a shorter day","authors":"Russell Deitrick, Colin Goldblatt","doi":"10.1038/s41561-024-01515-0","DOIUrl":"10.1038/s41561-024-01515-0","url":null,"abstract":"","PeriodicalId":19053,"journal":{"name":"Nature Geoscience","volume":"17 9","pages":"944-944"},"PeriodicalIF":15.7,"publicationDate":"2024-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s41561-024-01515-0.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141804913","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-23DOI: 10.1038/s41561-024-01500-7
Joseph B. Novak, Rocío P. Caballero-Gill, Rebecca M. Rose, Timothy D. Herbert, Harry J. Dowsett
Several modelling and observational studies suggest deep water formation in the subpolar North Pacific as a possible alternative mode of thermohaline circulation that occurred in the warm Pliocene, a time when global atmospheric partial pressure of carbon dioxide was like the modern atmosphere (~400 ppm). We test this hypothesis by measuring the δ13C of the benthic foraminifer Cibicidoides wuellerstorfi collected from northernmost Pacific mid-Piacenzian Warm Period (3.264–3.025 Myr ago) sediments. The data reveal progressively more isotopically negative dissolved inorganic carbon along a northward Equator-to-pole transect, the opposite of the expected Pliocene Pacific meridional overturning circulation signal. C. wuellerstorfi δ13C is also often more positive at the deeper Ocean Drilling Program (ODP) site 887 compared with the shallower ODP site 883, suggesting ‘bottom-up’ ventilation of the deep Pacific Ocean. We then present alkenone sea surface temperature and export-productivity data from ODP site 883, which suggest that late Pliocene subarctic North Pacific carbonate sedimentation was, at least in part, probably due to higher coccolithophore export production, rather than North Pacific Deep Water formation as previously argued. Therefore, we suggest it is unlikely that North Pacific Deep Water formation occurred in the mid-Piacenzian Warm Period, although a shallower overturning cell cannot be ruled out. Late Pliocene warmth did not lead to substantial deep water formation in the North Pacific as previously proposed, according to benthic foraminifera carbon isotope transects.
{"title":"Isotopic evidence against North Pacific Deep Water formation during late Pliocene warmth","authors":"Joseph B. Novak, Rocío P. Caballero-Gill, Rebecca M. Rose, Timothy D. Herbert, Harry J. Dowsett","doi":"10.1038/s41561-024-01500-7","DOIUrl":"10.1038/s41561-024-01500-7","url":null,"abstract":"Several modelling and observational studies suggest deep water formation in the subpolar North Pacific as a possible alternative mode of thermohaline circulation that occurred in the warm Pliocene, a time when global atmospheric partial pressure of carbon dioxide was like the modern atmosphere (~400 ppm). We test this hypothesis by measuring the δ13C of the benthic foraminifer Cibicidoides wuellerstorfi collected from northernmost Pacific mid-Piacenzian Warm Period (3.264–3.025 Myr ago) sediments. The data reveal progressively more isotopically negative dissolved inorganic carbon along a northward Equator-to-pole transect, the opposite of the expected Pliocene Pacific meridional overturning circulation signal. C. wuellerstorfi δ13C is also often more positive at the deeper Ocean Drilling Program (ODP) site 887 compared with the shallower ODP site 883, suggesting ‘bottom-up’ ventilation of the deep Pacific Ocean. We then present alkenone sea surface temperature and export-productivity data from ODP site 883, which suggest that late Pliocene subarctic North Pacific carbonate sedimentation was, at least in part, probably due to higher coccolithophore export production, rather than North Pacific Deep Water formation as previously argued. Therefore, we suggest it is unlikely that North Pacific Deep Water formation occurred in the mid-Piacenzian Warm Period, although a shallower overturning cell cannot be ruled out. Late Pliocene warmth did not lead to substantial deep water formation in the North Pacific as previously proposed, according to benthic foraminifera carbon isotope transects.","PeriodicalId":19053,"journal":{"name":"Nature Geoscience","volume":"17 8","pages":"795-802"},"PeriodicalIF":15.7,"publicationDate":"2024-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141750308","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-22DOI: 10.1038/s41561-024-01480-8
Andrew K. Sweetman, Alycia J. Smith, Danielle S. W. de Jonge, Tobias Hahn, Peter Schroedl, Michael Silverstein, Claire Andrade, R. Lawrence Edwards, Alastair J. M. Lough, Clare Woulds, William B. Homoky, Andrea Koschinsky, Sebastian Fuchs, Thomas Kuhn, Franz Geiger, Jeffrey J. Marlow
Deep-seafloor organisms consume oxygen, which can be measured by in situ benthic chamber experiments. Here we report such experiments at the polymetallic nodule-covered abyssal seafloor in the Pacific Ocean in which oxygen increased over two days to more than three times the background concentration, which from ex situ incubations we attribute to the polymetallic nodules. Given high voltage potentials (up to 0.95 V) on nodule surfaces, we hypothesize that seawater electrolysis may contribute to this dark oxygen production. Oxygen is generated abiotically at the abyssal seafloor in the presence of polymetallic nodules, potentially by seawater electrolysis, according to in situ chamber and ex situ incubation experiments.
{"title":"Evidence of dark oxygen production at the abyssal seafloor","authors":"Andrew K. Sweetman, Alycia J. Smith, Danielle S. W. de Jonge, Tobias Hahn, Peter Schroedl, Michael Silverstein, Claire Andrade, R. Lawrence Edwards, Alastair J. M. Lough, Clare Woulds, William B. Homoky, Andrea Koschinsky, Sebastian Fuchs, Thomas Kuhn, Franz Geiger, Jeffrey J. Marlow","doi":"10.1038/s41561-024-01480-8","DOIUrl":"10.1038/s41561-024-01480-8","url":null,"abstract":"Deep-seafloor organisms consume oxygen, which can be measured by in situ benthic chamber experiments. Here we report such experiments at the polymetallic nodule-covered abyssal seafloor in the Pacific Ocean in which oxygen increased over two days to more than three times the background concentration, which from ex situ incubations we attribute to the polymetallic nodules. Given high voltage potentials (up to 0.95 V) on nodule surfaces, we hypothesize that seawater electrolysis may contribute to this dark oxygen production. Oxygen is generated abiotically at the abyssal seafloor in the presence of polymetallic nodules, potentially by seawater electrolysis, according to in situ chamber and ex situ incubation experiments.","PeriodicalId":19053,"journal":{"name":"Nature Geoscience","volume":"17 8","pages":"737-739"},"PeriodicalIF":15.7,"publicationDate":"2024-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s41561-024-01480-8.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141737024","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-19DOI: 10.1038/s41561-024-01483-5
Jiaxin Xie, Xiaomang Liu, Scott Jasechko, Wouter R. Berghuijs, Kaiwen Wang, Changming Liu, Markus Reichstein, Martin Jung, Sujan Koirala
Groundwater-sustained baseflow is a vital source of river flow, especially during dry seasons. The proportion of river flow sustained by baseflow—the baseflow index—is essential for assessing fluvial nutrient cycling and contaminant transport. However, the global baseflow index remains highly uncertain, with current Earth system model simulations ranging from 12% to 94%. Here we estimate the global baseflow index to be 59% ± 7% based on an emergent constraint approach, which integrates 50 Earth system models with baseflow indices derived from streamflow observations in 15,567 basins. Our observational constraint indicates that at least 21% ± 3% of precipitation recharges groundwater, which is approximately double the figure reported in the Sixth Assessment Report of the United Nations Intergovernmental Panel on Climate Change. Thus, our research suggests a more active role of groundwater in the global water cycle than most Earth system models currently simulate. We present evidence that the considerable disagreement in simulated baseflow stems from unrealistic and varied model representations of infiltration, aquifer structure and groundwater dynamics. These processes should be prioritized so that models can capture active groundwater–river connections. Groundwater supplies about 59% of global river flow, suggesting a larger contribution of groundwater to the global water cycle than currently appreciated, according to an analysis integrating estimates from models and observations.
{"title":"Majority of global river flow sustained by groundwater","authors":"Jiaxin Xie, Xiaomang Liu, Scott Jasechko, Wouter R. Berghuijs, Kaiwen Wang, Changming Liu, Markus Reichstein, Martin Jung, Sujan Koirala","doi":"10.1038/s41561-024-01483-5","DOIUrl":"10.1038/s41561-024-01483-5","url":null,"abstract":"Groundwater-sustained baseflow is a vital source of river flow, especially during dry seasons. The proportion of river flow sustained by baseflow—the baseflow index—is essential for assessing fluvial nutrient cycling and contaminant transport. However, the global baseflow index remains highly uncertain, with current Earth system model simulations ranging from 12% to 94%. Here we estimate the global baseflow index to be 59% ± 7% based on an emergent constraint approach, which integrates 50 Earth system models with baseflow indices derived from streamflow observations in 15,567 basins. Our observational constraint indicates that at least 21% ± 3% of precipitation recharges groundwater, which is approximately double the figure reported in the Sixth Assessment Report of the United Nations Intergovernmental Panel on Climate Change. Thus, our research suggests a more active role of groundwater in the global water cycle than most Earth system models currently simulate. We present evidence that the considerable disagreement in simulated baseflow stems from unrealistic and varied model representations of infiltration, aquifer structure and groundwater dynamics. These processes should be prioritized so that models can capture active groundwater–river connections. Groundwater supplies about 59% of global river flow, suggesting a larger contribution of groundwater to the global water cycle than currently appreciated, according to an analysis integrating estimates from models and observations.","PeriodicalId":19053,"journal":{"name":"Nature Geoscience","volume":"17 8","pages":"770-777"},"PeriodicalIF":15.7,"publicationDate":"2024-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141725801","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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