Spatial patterns of benthic silica flux in the North Pacific reflect upper ocean production

Hou, Yi; Hammond, Douglas E.; Berelson, William M.; Kemnitz, Nathaniel; Adkins, Jess F.; Lunstrum, Abby

doi:10.1016/j.dsr.2019.04.013

Cited by 19 publications

(29 citation statements)

References 31 publications

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“…We conclude the following: The middepth silica maximum (lower NPDW) is largely flowing through the basin with minimal modification of concentration, primarily from water column dissolution, consistent with the original hypothesis of Edmond et al (1979). The increase in silica at the maximum toward the east along the Aleutian Trench creates an appearance of a focused source in the NEPB, but the vertical structure is largely established in the northwest Pacific via enhancement of an inherent middepth maximum that results from the greater “age” of the NPDW relative to the underlying UCDW, coupled with Bering Sea input. The near‐bottom maximum in the UCDW is created locally within the basin, consistent with the independent analysis of Hou et al (2019) based on benthic flux measurements and one‐dimensional modeling of the bottom 500 m of the water column. The addition of silica via the seafloor source occurs preferentially where neutral surfaces incrop into broadly upsloping topography, a structure associated with the southward geostrophic flow pathway east of 150°W. …”

Section: Discussionsupporting

confidence: 85%

“…For silica, the latitude dependence is particularly strong, as shown by benthic flux estimates from pore water profiles and core incubations, as well as a compilation of deep trap deployments (Hou et al, 2019). This compilation is used to estimate the Si rain at 1 km depth for each zone.…”

Section: Methodsmentioning

confidence: 99%

“…The 5% value is adopted here for Zones 1 and 2, with a value of 15% for Zone 3, based on trap data at Station P (50°N, 145°W; Honjo et al, 2008). Only a few percent of the silica rain is permanently buried (Hou et al, 2019), so the rain reaching the seafloor is assumed to diffuse back into the deepest layer from the upper sediments, creating a bottom source. A sensitivity experiment explored a different value for the fraction dissolving in the water column.…”

Section: Methodsmentioning

confidence: 99%

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Abyssal Pathways and the Double Silica Maximum in the Northeast Pacific Basin

Hautala

Hammond

2020

Geophysical Research Letters

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This study examines causes of the double silica maximum in the deep interior Northeast Pacific Basin using a stochastic Lagrangian tracer model based on steady-state advective fields and diapycnal diffusion established by a hydrographic inverse method that conserves potential vorticity and salinity. Lateral diffusion, unresolved by the inverse model, is adjusted for overall agreement with radiocarbon distribution. The double silica maximum in vertical profiles arises from an eastern-intensified single maximum in the North Pacific Deep Water along the northern domain boundary (originating in the western Pacific), and a strong subarctic bottom source supplying silica to Upper Circumpolar Deep Water density surfaces that successively intersect the seafloor over a broad area east of 150°W, associated geostrophically with southward flow. The existence of the double silica maximum requires weak diapycnal transport in the deep interior, with broader implications for the conceptual picture of meridional overturning circulation in the North Pacific. Plain Language Summary Silica, an important nutrient supporting diatom production, has two distinct vertical concentration maxima in the deep (>1,000 m) northeast Pacific ocean. This structure suggests that distinct processes create each of these features. In this study, we explore how large-scale deep ocean circulation, quantified by a recent study, combines with a simple latitude-dependent source of silica from seafloor sediments to create a near-bottom maximum within a southward current in the densest layers in the eastern half of the basin. In contrast, a shallower (middepth) silica maximum in the vertical structure of concentration profiles is already present in the inflowing deep water and is not substantially modified as it flows through this part of the ocean.

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Section: Discussionsupporting

confidence: 85%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Abyssal Pathways and the Double Silica Maximum in the Northeast Pacific Basin

Hautala

Hammond

2020

Geophysical Research Letters

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“…To understand the magnitude of dissolution, we first ask how much, and what type, of CaCO 3 is being produced and exported. A documented northward increase of CaCO 3 production and export across the North Pacific reflects the ecological shift between limited (low‐CaCO 3 ) picophytoplankton production in the oligotrophic subtropics, and high, coccolithophore‐ and diatom‐dominated, high‐CaCO 3 production in the subpolar region (Table 1, Dong et al., 2019; Endo et al., 2018; Hou et al., 2019; Juranek et al., 2012). We found that calcite production is overwhelmingly dominated by coccolithophores across the entire transect (Table 1, Ziveri et al., 2022).…”

Section: Resultsmentioning

confidence: 99%

Shallow Calcium Carbonate Cycling in the North Pacific Ocean

Subhas

Dong

Naviaux³

et al. 2022

Global Biogeochemical Cycles

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“…The transition zone between the gyres shifts seasonally between 32°N and 42°N (Ayers & Lozier, 2010; Polovina et al., 2017; Roden, 1991). At the time of CDisK‐IV, the transition zone chlorophyll front was located at 37°N (Hou et al., 2019). Dust blown from Asia is a major source of sediment and nutrients to the study area, particularly in the region between about 30 and 45°N (Buck et al., 2013; Ginoux et al., 2001; Jickells et al., 2005; Zender et al., 2003).…”

Section: Methodsmentioning

confidence: 99%

Variability in the Concentration of Lithium in the Indo‐Pacific Ocean

Steiner

Landing

Bohlin

et al. 2022

Global Biogeochemical Cycles

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Lithium has limited biological activity and can readily replace aluminium, magnesium and iron ions in aluminosilicates, making it a proxy for the inorganic silicate cycle and its potential link to the carbon cycle. Data from the North Pacific Ocean, tropical Indian Ocean, Southern Ocean and Red Sea suggest that salinity normalized dissolved lithium concentrations vary by up to 2%–3% in the Indo‐Pacific Ocean. The highest lithium concentrations were measured in surface waters of remote North Pacific and Indian Ocean stations that receive relatively high fluxes of dust. The lowest dissolved lithium concentrations were measured just below the surface mixed layer of the stations with highest surface water concentrations, consistent with removal into freshly forming aluminium rich phases and manganese oxides. In the North Pacific, water from depths >2,000 m is slightly depleted in lithium compared to the initial composition of Antarctic Bottom Water, likely due to uptake of lithium by authigenically forming aluminosilicates. The results of this study suggest that the residence time of lithium in the ocean may be significantly shorter than calculated from riverine and hydrothermal fluxes.

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Spatial patterns of benthic silica flux in the North Pacific reflect upper ocean production

Cited by 19 publications

References 31 publications

Abyssal Pathways and the Double Silica Maximum in the Northeast Pacific Basin

Abyssal Pathways and the Double Silica Maximum in the Northeast Pacific Basin

Shallow Calcium Carbonate Cycling in the North Pacific Ocean

Variability in the Concentration of Lithium in the Indo‐Pacific Ocean

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