Multi‐Elemental Tracers in the Amerasian Basin Reveal Interlinked Biogeochemical and Physical Processes in the Arctic Ocean Upper Halocline

Global Biogeochemical Cycles, Journal Year: 2025, Volume and Issue: 39(4)

Published: April 1, 2025

Abstract The physical and biogeochemical properties of the western Arctic Ocean are rapidly changing, resulting in cascading shifts to local ecosystems. nutrient‐rich Pacific water inflow through Bering Strait is modified on Chukchi East Siberian shelves by brine rejection during sea ice formation, a strong halocline (called Upper Halocline Layer (UHL)) that separates cold relatively fresh surface layer from warmer more saline (and nutrient‐poor) Atlantic‐derived below. Biogeochemical signals entrained into UHL result Waters sediment river influence shelf. In this synthesis, we bring together data 2015 U.S. GEOTRACES program implement multi‐tracer (dissolved particulate trace elements, radioactive stable isotopes, macronutrients, dissolved gas/atmospheric tracers) approach assess relative shelf sediments, rivers, seawater contribution Amerasian halocline. For each element, characterized their behavior as mixing dominated (e.g., dCu, dGa), shelf‐influenced dFe, dZn), or combination both dBa, dNi). Leveraging framework, assessed sources sinks contributing elemental distributions: sediments dZn, dCd, dHg), riverine sources, organic carbon), scavenging particles originating dMn, dV, etc.). Additionally, synthesized results isotopic atmospheric tracers yielded tracer age estimates for ranging between 1 2 decades spatial gradient consistent with cyclonic circulation.

Language: Английский

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Silicon Isotopes Highlight the Role of Glaciated Fjords in Modifying Coastal Waters

Journal of Geophysical Research Biogeosciences, Journal Year: 2023, Volume and Issue: 128(7)

Published: June 12, 2023

Abstract Glaciers and ice sheets are experiencing rapid warming under current climatic change there is increasing evidence that glacial meltwaters provide key dissolved dissolvable amorphous nutrients to downstream ecosystems. However, large debate exists around the fate of these within complex heterogenous fjord environments, where biogeochemical cycling still often poorly understood. We combine silicon (Si) concentration data with isotopic compositions better understand export in two contrasting fjordic environments south‐west Greenland. show both fjords have isotopically light (DSi) surface waters, despite an apparently biological drawdown DSi salinity. hypothesize such observations cannot be explained by simple water mass mixing processes, postulate source Si, most likely glacially derived silica (ASi), responsible for further modifying coastal waters beyond. Fjord exchange a relatively slow process (several months), thus less impacted short‐term (<seasonal) changes meltwater input into fjord, which has implications when considering role on nutrient beyond shelf break. highlight need studies combined particulate analysis more detailed cycles highly dynamic environments.

Language: Английский

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Detrital Input Sustains Diatom Production off a Glaciated Arctic Coast

Geophysical Research Letters, Journal Year: 2024, Volume and Issue: 51(12)

Published: June 12, 2024

Abstract In the Arctic and subarctic oceans, relatively low supply of silicon (compared to other nutrients) can make it limiting for growth diatoms, a fundamental building block oceanic food web. Glaciers release large quantities dissolved dissolvable solid amorphous silica phases into high‐latitude estuaries (fjords), but role these glacially‐derived in sustaining diatom coastal open‐water sectors remains unknown. Here we show how stable radiogenic isotopes be used together address this question, using southwest Greenland as case study. This study finds enhanced levels detrital (i.e., mineral) silica, likely glacially‐sourced, portion observed off coast, revealing phytoplankton community function during high‐meltwater periods.

Language: Английский

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The Importance of Riverine Nutrient Supply for the Marine Silica Pump of Arctic Shelves: Evidence From the Laptev Sea

Global Biogeochemical Cycles, Journal Year: 2024, Volume and Issue: 38(4)

Published: March 27, 2024

Abstract Arctic shelves receive a large load of nutrients from rivers, which play major role in the biogeochemical cycles Ocean. In this study, we present measurements dissolved silicon isotopes (δ 30 Si(OH) 4 ) around Laptev Sea and surface waters Eurasian collected October 2018 to document terrestrial modifications on their contribution basin. Nitrogen was found be depleted limiting nutrient primary production Sea, allowing excess export central Heavy δ water column linked strong biological removal DSi shelves, enabled by vigorous N recycling. From isotopically constrained processes, estimate that >50% riverine inputs is removed within Lena River delta shelf. Extrapolating Siberian leads an 2.5 ± 0.8 kmol/s through Transpolar Drift. An updated isotopic budget Ocean reproduces observed signatures out underlines importance processes modulating export. Given opal burial fluxes Artic are controlled denitrification N‐limitation, these sensitive ongoing climate change. As consequence higher shelf responding productivity, it inferred could increase future, accompanied lighter signatures.

Language: Английский

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Benthic silicon cycling in the Arctic Barents Sea: a reaction–transport model study

Biogeosciences, Journal Year: 2022, Volume and Issue: 19(14), P. 3445 - 3467

Published: July 21, 2022

Abstract. Over recent decades the highest rates of water column warming and sea ice loss across Arctic Ocean have been observed in Barents Sea. These physical changes resulted rapid ecosystem adjustments, manifesting as a northward migration temperate phytoplankton species at expense silica-based diatoms. will potentially alter composition phytodetritus deposited seafloor, which acts biogeochemical reactor is pivotal recycling key nutrients, such silicon (Si). To appreciate sensitivity Sea benthic system to surface primary production, there need better understand this benthic–pelagic coupling. Stable Si isotopic compositions sediment pore waters solid phase from three stations reveal coupling iron (Fe) cycles, contemporaneous dissolution lithogenic silicate minerals (LSi) alongside biogenic silica (BSi), potential for reprecipitation dissolved silicic acid (DSi) authigenic clay (AuSi). However, reaction cannot be quantified observational data alone, mechanistic understanding factors control these processes missing. Here, we employ reaction–transport modelling together with disentangle pathways controlling cycling within seafloor. Processes BSi are active on multiple timescales, ranging weeks hundreds years, able examine through steady state transient model runs. Steady simulations show that 60 % 98 DSi pool may sourced LSi, while also strongly influenced by desorption metal oxides, most likely Fe (oxyhydr)oxides (FeSi), they reductively dissolve. Further, our indicate between 2.9 37 released into subsequently removed process has fractionation factor approximately −2 ‰, representing AuSi. observations significant LSi represents source new ocean precipitation AuSi an additional sink, could address imbalances current regional budget. Lastly, suggests least one-third total annual flux more reactive, diatom-derived after bloom marginal zone. This subject change continued Atlantic species, retreat zone decline inventory subpolar North over last 3 decades.

Language: Английский

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Nutrient and Silicon Isotope Dynamics in the Laptev Sea and Implications for Nutrient Availability in the Transpolar Drift

Global Biogeochemical Cycles, Journal Year: 2022, Volume and Issue: 36(9)

Published: Sept. 1, 2022

Abstract Realistic prediction of the near‐future response Arctic Ocean primary productivity to ongoing warming and sea ice loss requires a mechanistic understanding processes controlling nutrient bioavailability. To evaluate continental inputs, biological utilization, influence mixing winter in Laptev Sea, major source region Transpolar Drift (TPD), we compare observed with preformed concentrations dissolved inorganic nitrogen (DIN) phosphorus (DIP), silicic acid (DSi), silicon isotope compositions DSi (δ 30 Si ) obtained for two summers (2013 2014) one (2012). In summer, persisted surface layer southeastern while diatom‐dominated utilization caused intense northward drawdown pronounced shift δ from +0.91 +3.82‰. The modeled fractionation suggests that northern Sea originated Lena River was supplied during spring freshet, riverine continuously summer. Primary fueled by river‐borne nutrients enhanced admixture DIN‐ DIP‐rich Atlantic‐sourced waters surface, either convective previous or occasional storm‐induced stratification breakdowns late Substantial enrichments (+240%) DIP (+90%) beneath plume were ice‐driven redistribution remineralization. Predicted weaker on outer Shelf will enhance removal through greater vertical DIN supply, which limit export reduce TPD.

Language: Английский

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Sea Ice as a Factor of Primary Production in the European Arctic: Phytoplankton Size Classes and Carbon Fluxes

Journal of Marine Science and Engineering, Journal Year: 2023, Volume and Issue: 11(11), P. 2131 - 2131

Published: Nov. 8, 2023

The seasonally ice-covered marine region of the European Arctic has experienced warming and sea ice loss in last two decades. During expeditions August 2020 2021, new data on size-fractioned primary production (PP), chlorophyll a concentration, phytoplankton biomass composition carbon fixation rates dark were obtained marginal zone (MIZ) Barents Sea, Nansen Basin Greenland Sea to better understand response ecosystems ongoing climate changes. Four different situations observed study region: (i) bloom large-cell diatom Podosira glacialis, whose was trapped strong halocline at edge dense cover; (ii) chain-like colonies Thalassiosira diatoms shelf mixed waters fields shallow that could be supported by “fresh” elements polynya condition, as well terrestrial run-off drifting ices; late stage, this accompanied intensive growth Phaeocystis pouchetti; (iii) dominance small-cell under weakened stratification significant influence Atlantic water, depleted microelements silicates; (iv) dinoflagellates eutrophic water contact between masses origin clear conditions increased light intensity. >10 µm cell size group its relative contribution PP stratification, nutrient load associated with conditions. Small sizes < 2 formed basis total MIZ regardless state ice.

Language: Английский

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A silicon isotopic perspective on the contribution of diagenesis to the sedimentary silicon budget in the Southern Ocean

Geochimica et Cosmochimica Acta, Journal Year: 2022, Volume and Issue: 327, P. 298 - 313

Published: April 22, 2022

Diatoms are known to fractionate silicon isotopes during the formation of their frustules causing isotopic composition biogenic silica track degree silicic acid consumption in surface waters. Despite a growing body work that uses this proxy reconstruct past changes utilization, understanding benthic cycle, particularly identification and quantification processes potentially alter early diagenesis is still lacking. We investigated these by comparing pore water acid, and, for first time, lithogenic from five sediment cores collected deep basin Southern Ocean representing diversity sedimentation regimes. Silicic concentrations waters were result dynamic balance between dissolution silica, reactive phases Si re-precipitation with relative importance each differing significantly regions. The results consistent authigenic alumino-silicates derived dissolved Sub-Antarctic Zone Antarctic (on average 12 ± 5% 17 13%, respectively). Since latter process can isotopes, implies that, even if diatoms preserved sediments reliable utilization ocean, care must be taken extract clean phase free clays eliminate potential bias when interpreting records.

Language: Английский

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A Refinement of the Processes Controlling Dissolved Copper and Nickel Biogeochemistry: Insights From the Pan‐Arctic

Journal of Geophysical Research Oceans, Journal Year: 2022, Volume and Issue: 127(5)

Published: April 26, 2022

Abstract Recent studies, including many from the GEOTRACES program, have expanded our knowledge of trace metals in Arctic Ocean, an isolated ocean dominated by continental shelf and riverine inputs. Here, we report a unique, pan‐Arctic linear relationship between dissolved copper (Cu) nickel (Ni) present north 60°N that is absent other oceans. The correlation driven primarily high Cu Ni concentrations low salinity, river‐influenced surface low, homogeneous deep waters, opposing their typical global distributions. Rivers are major source both metals, which most evident within central Arctic's Transpolar Drift. Local decoupling Cu‐Ni along Chukchi Shelf Canada Basin upper halocline reveals additionally modified biological cycling sediment processes, while mostly sourced inputs influenced mixing. This observation highlights differences chemistries: more prone to complexation with organic ligands, stabilizing its fluxes into Arctic, labile processes. Within Canadian Archipelago, important water Atlantic contributions meteoric waters attenuated during transit Atlantic. Additionally, diminish age due isolation sources, higher younger Eastern basins lower older Western basins.

Language: Английский

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Atypical Seasonality of the Silicon Cycle in the Yellow River Estuary and Bohai Sea Revealed by Stable Silicon Isotopes

Global Biogeochemical Cycles, Journal Year: 2024, Volume and Issue: 38(3)

Published: March 1, 2024

Abstract Biogeochemical Si cycle in coastal areas is of vital importance due to its close link with the carbon cycle. However, has been heavily perturbated by human activities. In this study, we studied spatiotemporal distribution biogenic (BSi) and dissolved (DSi) combined stable isotopes DSi (δ 30 ) Yellow River estuary Bohai Sea, one most populated world. Over an annual cycle, BSi concentrations varied from 0 43.5 μmol L −1 0.3 40 , respectively. This was associated large δ variations +0.49 ± 0.22‰ (2sd) spring +2.92 0.14‰ winter, which opposed observations that summer values were usually higher than those winter. atypical variation could be attributed water‐sediment regulation on occurring every early summer, leading a strong water mixing pattern suppressing diatom production summer. further prolonged extreme autumn rainfall land. The pulse supply nutrients subsequently enhanced primary productivity through spring, resuspended seafloor sediments likely important source <−0.5‰. Our findings suggest natural seasonality greatly masked activities climate events Sea. study serves as reference research endeavors worldwide for revealing overlaying effect anthropogenic consequences variability.

Language: Английский

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