What proportion of riverine nutrients reaches the open ocean?

Sharples, Jonathan; Middelburg, Jack J.; Fennel, Katja; Jickells, Timothy D.

doi:10.1002/2016gb005483

Cited by 132 publications

(147 citation statements)

References 89 publications

Supporting

Mentioning

130

Contrasting

Unclassified

Order By: Relevance

“…The world's coral reefs have undoubtedly been subjected to natural and anthropogenic disturbances and are being degraded [1][2][3][4][5][6]. It is now well established that the ecological health of the coral reefs is under stress from threats associated with climate change and terrestrial runoff [2][3][4][5][7][8][9].…”

Section: Introductionmentioning

confidence: 99%

Characterisation of Hydrological Response to Rainfall at Multi Spatio-Temporal Scales in Savannas of Semi-Arid Australia

Jarihani

Sidle

Bartley

et al. 2017

Water

View full text Add to dashboard Cite

Abstract:Rainfall is the main driver of hydrological processes in dryland environments and characterising the rainfall variability and processes of runoff generation are critical for understanding ecosystem function of catchments. Using remote sensing and in situ data sets, we assess the spatial and temporal variability of the rainfall, rainfall-runoff response, and effects on runoff coefficients of antecedent soil moisture and ground cover at different spatial scales. This analysis was undertaken in the Upper Burdekin catchment, northeast Australia, which is a major contributor of sediment and nutrients to the Great Barrier Reef. The high temporal and spatial variability of rainfall are found to exert significant controls on runoff generation processes. Rainfall amount and intensity are the primary runoff controls, and runoff coefficients for wet antecedent conditions were higher than for dry conditions. The majority of runoff occurred via surface runoff generation mechanisms, with subsurface runoff likely contributing little runoff due to the intense nature of rainfall events. MODIS monthly ground cover data showed better results in distinguishing effects of ground cover on runoff that Landsat-derived seasonal ground cover data. We conclude that in the range of moderate to large catchments (193-36,260 km 2 ) runoff generation processes are sensitive to both antecedent soil moisture and ground cover. A higher runoff-ground cover correlation in drier months with sparse ground cover highlighted the critical role of cover at the onset of the wet season (driest period) and how runoff generation is more sensitive to cover in drier months than in wetter months. The monthly water balance analysis indicates that runoff generation in wetter months (January and February) is partially influenced by saturation overland flow, most likely confined to saturated soils in riparian corridors, swales, and areas of shallow soil. By March and continuing through October, the soil "bucket" progressively empties by evapotranspiration, and Hortonian overland flow becomes the dominant, if not exclusive, flow generation process. The results of this study can be used to better understand the rainfall-runoff relationships in dryland environments and subsequent exposure of coral reef ecosystems in Australia and elsewhere to terrestrial runoff.

show abstract

Section: Introductionmentioning

confidence: 99%

Characterisation of Hydrological Response to Rainfall at Multi Spatio-Temporal Scales in Savannas of Semi-Arid Australia

Jarihani

Sidle

Bartley

et al. 2017

Water

View full text Add to dashboard Cite

show abstract

“…Recently, Sharples et al (2017) proposed a simple parameterization to describe riverine export to the open ocean based on the ratio of a plume's width (assumed to scale with the internal Rossby radius of deformation) to the local shelf width, which they define as the S P number. When a plume extends beyond the shelf, Sharples et al (2017) predict that the material will be exported to the open ocean directly within the plume.…”

Section: Introductionmentioning

confidence: 99%

“…When a plume extends beyond the shelf, Sharples et al (2017) predict that the material will be exported to the open ocean directly within the plume. Conversely, if the shelf is wider than the plume, no direct cross-shelf transport is expected to occur.…”

Section: Introductionmentioning

confidence: 99%

“…We expand upon the previous work and address a few of its limitations. Specifically, the relationship by Sharples et al (2017) is based solely on theoretical scaling arguments and uses the S P number as a binary metric (i.e., export is assumed to be either complete or nonexistent for any given plume) instead of providing a continuous relationship to describe a given plume's export. Here we present a detailed numerical study with the goal of finding empirical parameterizations for cross-shelf and alongshore export, as well as the timescales of export, based on the S P number and other riverine properties (e.g., discharge).…”

Section: Introductionmentioning

confidence: 99%

“…Global biogeochemical models cannot resolve the relatively small-scale processes governing river plume dynamics and cross-shelf export; instead, river inputs are often parameterized assuming an "all or nothing" approach. Recently, Sharples et al (2017), https://doi.org/10.1002/2016GB005483 proposed the S P number-a dimensionless number relating the estimated size of a plume as a function of latitude to the local shelf width-as a simple estimator of cross-shelf export. We extend their work, which is solely based on theoretical and empirical scaling arguments, and address some of its limitations using a numerical model of an idealized river plume.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Estimating the Cross‐Shelf Export of Riverine Materials: Part 1. General Relationships From an Idealized Numerical Model

Izett

Fennel

2018

Global Biogeochemical Cycles

Self Cite

View full text Add to dashboard Cite

Rivers deliver large amounts of terrestrially derived materials (such as nutrients, sediments, and pollutants) to the coastal ocean, but a global quantification of the fate of this delivery is lacking. Nutrients can accumulate on shelves, potentially driving high levels of primary production with negative consequences like hypoxia, or be exported across the shelf to the open ocean where impacts are minimized. Global biogeochemical models cannot resolve the relatively small‐scale processes governing river plume dynamics and cross‐shelf export; instead, river inputs are often parameterized assuming an “all or nothing” approach. Recently, Sharples et al. (2017), https://doi.org/10.1002/2016GB005483 proposed the SP number—a dimensionless number relating the estimated size of a plume as a function of latitude to the local shelf width—as a simple estimator of cross‐shelf export. We extend their work, which is solely based on theoretical and empirical scaling arguments, and address some of its limitations using a numerical model of an idealized river plume. In a large number of simulations, we test whether the SP number can accurately describe export in unforced cases and with tidal and wind forcings imposed. Our numerical experiments confirm that the SP number can be used to estimate export and enable refinement of the quantitative relationships proposed by Sharples et al. We show that, in general, external forcing has only a weak influence compared to latitude and derive empirical relationships from the results of the numerical experiments that can be used to estimate riverine freshwater export to the open ocean.

show abstract

A reevaluation of the magnitude and impacts of anthropogenic atmospheric nitrogen inputs on the ocean

Jickells

Buitenhuis

Altieri

et al. 2017

Global Biogeochemical Cycles

Self Cite

200

169

View full text Add to dashboard Cite

We report a new synthesis of best estimates of the inputs of fixed nitrogen to the world ocean via atmospheric deposition and compare this to fluvial inputs and dinitrogen fixation. We evaluate the scale of human perturbation of these fluxes. Fluvial inputs dominate inputs to the continental shelf, and we estimate that about 75% of this fluvial nitrogen escapes from the shelf to the open ocean. Biological dinitrogen fixation is the main external source of nitrogen to the open ocean, i.e., beyond the continental shelf. Atmospheric deposition is the primary mechanism by which land-based nitrogen inputs, and hence human perturbations of the nitrogen cycle, reach the open ocean. We estimate that anthropogenic inputs are currently leading to an increase in overall ocean carbon sequestration of~0.4% (equivalent to an uptake of 0.15 Pg C yr À1 and less than the Duce et al. (2008) estimate). The resulting reduction in climate change forcing from this ocean CO 2 uptake is offset to a small extent by an increase in ocean N 2 O emissions. We identify four important feedbacks in the ocean atmosphere nitrogen system that need to be better quantified to improve our understanding of the perturbation of ocean biogeochemistry by atmospheric nitrogen inputs. These feedbacks are recycling of (1) ammonia and (2) organic nitrogen from the ocean to the atmosphere and back, (3) the suppression of nitrogen fixation by increased nitrogen concentrations in surface waters from atmospheric deposition, and (4) increased loss of nitrogen from the ocean by denitrification due to increased productivity stimulated by atmospheric inputs.

show abstract

What proportion of riverine nutrients reaches the open ocean?

Cited by 132 publications

References 89 publications

Characterisation of Hydrological Response to Rainfall at Multi Spatio-Temporal Scales in Savannas of Semi-Arid Australia

Characterisation of Hydrological Response to Rainfall at Multi Spatio-Temporal Scales in Savannas of Semi-Arid Australia

Estimating the Cross‐Shelf Export of Riverine Materials: Part 1. General Relationships From an Idealized Numerical Model

A reevaluation of the magnitude and impacts of anthropogenic atmospheric nitrogen inputs on the ocean

Contact Info

Product

Resources

About