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Water column
About: Water column is a research topic. Over the lifetime, 13706 publications have been published within this topic receiving 496626 citations.
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TL;DR: In this article, a global compilation of dissolved-iron observations was used to provide insights into the processes controlling iron distributions and some constraints for ocean biogeochemical models, where an improved particle scavenging parameterization, based on the sinking mass flux of particulate organic material, biogenic silica, calcium carbonate, and mineral dust particles, was proposed to improve simulation of the iron cycle within a global-scale, Biogeochemical Elemental Cycling ocean model.
Abstract: . Analysis of a global compilation of dissolved-iron observations provides insights into the processes controlling iron distributions and some constraints for ocean biogeochemical models. The distribution of dissolved iron appears consistent with the conceptual model developed for Th isotopes, whereby particle scavenging is a two-step process of scavenging mainly by colloidal and small particulates, followed by aggregation and removal on larger sinking particles. Much of the dissolved iron ( ~0.02 μm) and, thus, is subject to aggregation and scavenging removal. This implies distinct scavenging regimes for dissolved iron consistent with the observations: 1) a high scavenging regime – where dissolved-iron concentrations exceed the concentrations of strongly binding organic ligands; and 2) a moderate scavenging regime – where dissolved iron is bound to both colloidal and soluble ligands. Within the moderate scavenging regime, biological uptake and particle scavenging decrease surface iron concentrations to low levels ( We use the observational database to improve simulation of the iron cycle within a global-scale, Biogeochemical Elemental Cycling (BEC) ocean model. Modifications to the model include: 1) an improved particle scavenging parameterization, based on the sinking mass flux of particulate organic material, biogenic silica, calcium carbonate, and mineral dust particles; 2) desorption of dissolved iron from sinking particles; and 3) an improved sedimentary source for dissolved iron. Most scavenged iron (90%) is put on sinking particles to remineralize deeper in the water column. The model-observation differences are reduced with these modifications. The improved BEC model is used to examine the relative contributions of mineral dust and marine sediments in driving dissolved-iron distributions and marine biogeochemistry. Mineral dust and sedimentary sources of iron contribute roughly equally, on average, to dissolved iron concentrations. The sedimentary source from the continental margins has a strong impact on open-ocean iron concentrations, particularly in the North Pacific. Plumes of elevated dissolved-iron concentrations develop at depth in the Southern Ocean, extending from source regions in the SW Atlantic and around New Zealand. The lower particle flux and weaker scavenging in the Southern Ocean allows the continental iron source to be advected far from sources. Both the margin sediment and mineral dust Fe sources substantially influence global-scale primary production, export production, and nitrogen fixation, with a stronger role for the dust source. Ocean biogeochemical models that do not include the sedimentary source for dissolved iron, will overestimate the impact of dust deposition variations on the marine carbon cycle. Available iron observations place some strong constraints on ocean biogeochemical models. Model results should be evaluated against both surface and subsurface Fe observations in the waters that supply dissolved iron to the euphotic zone.
372 citations
TL;DR: In this article, the authors measured in situ with benthic chambers averages 49 and 163 μmol · m −2 · hr −1 during November-May and June-October respectively.
370 citations
TL;DR: In this paper, the dominant fate of dissolved organic carbon (DOC) released from permafrost soils to inland waters is either complete oxidation to CO2 or partial oxidation and river export to oceans.
Abstract: Carbon in thawing permafrost soils may have global impacts on climate change; however, the factors that control its processing and fate are poorly understood. The dominant fate of dissolved organic carbon (DOC) released from soils to inland waters is either complete oxidation to CO2 or partial oxidation and river export to oceans. Although both processes are most often attributed to bacterial respiration, we found that photochemical oxidation exceeds rates of respiration and accounts for 70 to 95% of total DOC processed in the water column of arctic lakes and rivers. At the basin scale, photochemical processing of DOC is about one-third of the total CO2 released from surface waters and is thus an important component of the arctic carbon budget.
369 citations
TL;DR: In this article, the relationship between photosynthetic rate at light saturation and chlorophyll content in natural populations and cultures of marine phytoplankton was determined, and a mean value of 3.7 g C assimilated/hour/g chlorophyLL was obtained from the experimental results and from data present in the literature.
Abstract: The relationship was determined between photosynthetic rate at light saturation and chlorophyll content in natural populations and cultures of marine phytoplankton. A mean value of 3.7 g C assimilated/hour/g chlorophyll was obtained from the experimental results and from data present in the literature.
A method is described by means of which organic production beneath a unit of sea surface may be estimated from the chlorophyll content of the water, the total daily solar radiation reaching the sea surface, and the extinction coefficient of visible light in the water column. Production values calculated by this method are compared with values obtained by in situ productivity measurements.
368 citations
TL;DR: In this article, it was estimated that 92% of coccoliths produced in the euphotic layer were thus being transported to the deep-sea bottom, and the majority of freed coccolith will be dissolved in the undersaturated water column before arriving at the bottom.
367 citations