Remote sensing of primary production in the ocean: promise and fulfilment

1995 ◽  
Vol 348 (1324) ◽  
pp. 191-202 ◽  
Keyword(s):  
Remote Sensing ◽  
Primary Production ◽  
North Atlantic ◽  
Local Algorithm ◽  
Ocean Colour ◽  
Remotely Sensed Data ◽  
Local Algorithms ◽  
The North ◽  
Basin Scale ◽  
The North Atlantic

Remote sensing of ocean colour affords us our only window into the synoptic state of the pelagic ecosystem, and is likely to remain the only such option into the foreseeable future. Estimation of primary production from remotely sensed data on ocean colour is a research problem in two parts: (i) the construction of a local algorithm; and (ii) the development of a protocol for extrapolation. Good local algorithms exist but their proper implementation requires that certain parameters be specified. Protocols for extrapolation have to include procedures for the assignment of these parameters. One suitable approach is based on partition of the ocean into a suite of domains and provinces within which physical forcing, and the algal response to it, are distinct. This approach is still in its infancy, but is best developed for the North Atlantic. Using this method, and using the accumulated data from oceanographic expeditions, leads to an estimate for the annual primary production of the North Atlantic at the basin scale. Direct validation of the result is not possible in the absence of an independent calculation, but the potential errors involved may be assessed.

The Marine Environment

2017 ◽  
Author(s):  
N. Penny Holliday ◽  
Stephanie Henson
Keyword(s):  
Primary Production ◽  
North Atlantic ◽  
Physical Environment ◽  
Seasonal Cycle ◽  
Physical Processes ◽  
The North ◽  
Basin Scale ◽  
The North Atlantic ◽  
Physical Features ◽  
Growth Distribution

The growth, distribution, and variability of phytoplankton populations in the North Atlantic are primarily controlled by the physical environment. This chapter provides an overview of the regional circulation of the North Atlantic, and an introduction to the key physical features and processes that affect ecosystems, and especially plankton, via the availability of light and nutrients. There is a natural seasonal cycle in primary production driven by physical processes that determine the light and nutrient levels, but the pattern has strong regional variations. The variations are determined by persistent features on the basin scale (e.g. the main currents and mixed layer regimes of the subtropical and subpolar gyres), as well as transient mesoscale features such as eddies and meanders of fronts.

scholarly journals A New Method for Tracking Meddies by Satellite Altimetry

2014 ◽  
Vol 31 (6) ◽  
pp. 1434-1445 ◽  
Author(s):  
Federico Ienna ◽  
Young-Heon Jo ◽  
Xiao-Hai Yan
Keyword(s):  
Remote Sensing ◽  
Atlantic Ocean ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Saline Water ◽  
Ensemble Empirical Mode Decomposition ◽  
Altimeter Data ◽  
In Situ Techniques ◽  
The North ◽  
The North Atlantic

Abstract Subsurface coherent vortices in the North Atlantic, whose saline water originates from the Mediterranean Sea and which are known as Mediterranean eddies (meddies), have been of particular interest to physical oceanographers since their discovery, especially for their salt and heat transport properties into the North Atlantic Ocean. Many studies in the past have been successful in observing and studying the typical properties of meddies by probing them with in situ techniques. The use of remote sensing techniques would offer a much cheaper and easier alternative for studying these phenomena, but only a few past studies have been able to study meddies by remote sensing, and a reliable method for observing them remotely remains elusive. This research presents a new way of locating and tracking meddies in the North Atlantic Ocean using satellite altimeter data. The method presented in this research makes use of ensemble empirical mode decomposition (EEMD) as a means to isolate the surface expressions of meddies on the ocean surface and separates them from any other surface constituents, allowing robust meddies to be consistently tracked by satellite. One such meddy is successfully tracked over a 6-month time period (2 November 2005 to 17 May 2006). Results of the satellite tracking method are verified using expendable bathythermographs (XBT).

Decadal Evolution of Ocean Thermal Anomalies in the North Atlantic: The Effects of Ekman, Overturning, and Horizontal Transport

2014 ◽  
Vol 27 (2) ◽  
pp. 698-719 ◽  
Author(s):  
Richard G. Williams ◽  
Vassil Roussenov ◽  
Doug Smith ◽  
M. Susan Lozier
Keyword(s):  
North Atlantic ◽  
Volume Transport ◽  
Meridional Overturning Circulation ◽  
Ekman Transport ◽  
Dynamical Analysis ◽  
Thermal Anomalies ◽  
The North ◽  
Basin Scale ◽  
The North Atlantic ◽  
Induced Changes

Abstract Basin-scale thermal anomalies in the North Atlantic, extending to depths of 1–2 km, are more pronounced than the background warming over the last 60 years. A dynamical analysis based on reanalyses of historical data from 1965 to 2000 suggests that these thermal anomalies are formed by ocean heat convergences, augmented by the poorly known air–sea fluxes. The heat convergence is separated into contributions from the horizontal circulation and the meridional overturning circulation (MOC), the latter further separated into Ekman and MOC transport minus Ekman transport (MOC-Ekman) cells. The subtropical thermal anomalies are mainly controlled by wind-induced changes in the Ekman heat convergence, while the subpolar thermal anomalies are controlled by the MOC-Ekman heat convergence; the horizontal heat convergence is generally weaker, only becoming significant within the subpolar gyre. These thermal anomalies often have an opposing sign between the subtropical and subpolar gyres, associated with opposing changes in the meridional volume transport driving the Ekman and MOC-Ekman heat convergences. These changes in gyre-scale convergences in heat transport are probably induced by the winds, as they correlate with the zonal wind stress at gyre boundaries.

scholarly journals Importance of dissolved organic nitrogen in the North Atlantic Ocean in sustaining primary production: a 3-D modelling approach

2008 ◽  
Vol 5 (2) ◽  
pp. 1727-1764 ◽  
Author(s):  
G. Charria ◽  
I. Dadou ◽  
J. Llido ◽  
M. Drévillon ◽  
V. Garçon
Keyword(s):  
Atlantic Ocean ◽  
Primary Production ◽  
North Atlantic ◽  
Dissolved Organic Nitrogen ◽  
Organic Nitrogen ◽  
North Atlantic Ocean ◽  
Subtropical Gyre ◽  
Ekman Transport ◽  
The North ◽  
The North Atlantic

Abstract. An eddy-permitting coupled ecosystem-circulation model including dissolved organic matter is used to estimate the dissolved organic nitrogen (DON) supply sustaining primary production in the subtropical North Atlantic Ocean. After an analysis of the coupled model performances compared to the data, a sensitivity study demonstrates the strong impact of parameter values linked to the hydrolysis of particulate organic nitrogen and remineralisation of dissolved organic nitrogen on surface biogeochemical concentrations. The physical transport of dissolved organic nitrogen contributes to maintain the level of primary production in this subtropical gyre. It is dominated by the meridional component. We estimate a meridional net input of 0.039 molN.m−2.yr−1 over the domain (13°–35° N and 71–40° W) in the subtropical gyre. This supply is driven by the Ekman transport in the southern part and by non-Ekman transport (meridional current components, eddies, meanders and fronts) in the northern part of the subtropical gyre. At 12° N, our estimate (18 kmolN.s-1) confirms the estimation (17.9 kmolN.s-1) made by Roussenov et al. (2006) using a simplified biogeochemical model in a large scale model. This DON meridional input is within the range (from 0.05 up to 0.24 molN.m−2.yr-1) (McGillicuddy and Robinson, 1997; Oschlies, 2002) of all other possible mechanisms (mesoscale activity, nitrogen fixation, atmospheric deposition) fuelling primary production in the subtropical gyre. The present study confirms that the lateral supply of dissolved organic nitrogen might be important in closing the N budget over the North Atlantic Ocean and quantifies the importance of meridional input of dissolved organic nitrogen.

scholarly journals Systematic Conservation Planning at an Ocean Basin Scale: Identifying a Viable Network of Deep-Sea Protected Areas in the North Atlantic and the Mediterranean

2021 ◽  
Vol 8 ◽  
Author(s):  
Magali Combes ◽  
Sandrine Vaz ◽  
Anthony Grehan ◽  
Telmo Morato ◽  
Sophie Arnaud-Haond ◽  
...  
Keyword(s):  
Fish Species ◽  
North Atlantic ◽  
Conservation Planning ◽  
Deep Sea ◽  
Demersal Fish ◽  
Systematic Conservation Planning ◽  
The North ◽  
Basin Scale ◽  
The North Atlantic ◽  
Conservation Network

Designing conservation networks requires a well-structured framework for achieving essential objectives such as connectivity, replication or viability, and for considering local management and socioeconomic stakes. Although systematic conservation planning (SCP) approaches are increasingly used to inform such networks, their application remains challenging in large and poorly researched areas. This is especially the case in the deep sea, where SCP has rarely been applied, although growing awareness of the vulnerability of deep-sea ecosystems urges the implementation of conservation measures from local to international levels. This study aims to structure and evaluate a framework for SCP applicable to the deep sea, focusing on the identification of conservation priority networks for vulnerable marine ecosystems (VMEs), such as cold-water coral reefs, sponge grounds, or hydrothermal vents, and for key demersal fish species. Based on multi-objective prioritization, different conservation scenarios were investigated, allowing the impact of key elements such as connectivity and conservation cost to be evaluated. Our results show that continental margin slopes, the Mid-Atlantic Ridge, and deeper areas of large and productive shelves housing fishing grounds appeared as crucial zones for preserving the deep-sea biodiversity of the North Atlantic, and within the limitations imposed by the data available, of the Mediterranean. Using biologically-informed connectivity led to a more continuous and denser conservation network, without increasing the network size. Even when minimizing the overlap with socioeconomic activities, the inclusion of exploited areas was necessary to fulfil conservation objectives. Such areas included continental shelf fishing grounds for demersal fish species, and areas covered by deep-sea mining exploration contracts for hydrothermal vent communities. Covering 17% of the study area and protecting 55% of each feature on average, the identified priority network held a high conservation potential. However, these areas still suffer from poor protection, with 30% of them benefiting from some form of recognition and 11% only from protection against trawling. Integrating them into current marine spatial planning (MSP) discussions could foster the implementation of a basin-scale conservation network for the deep sea. Overall, this work established a framework for developing large-scale systematic planning, useful for managing Areas Beyond National Jurisdiction (ABNJ).

scholarly journals Toward a multivariate reanalysis of the North Atlantic Ocean biogeochemistry during 1998–2006 based on the assimilation of SeaWiFS chlorophyll data

Ocean Science ◽  
2013 ◽  
Vol 9 (1) ◽  
pp. 37-56 ◽  
Author(s):  
C. Fontana ◽  
P. Brasseur ◽  
J.-M. Brankart
Keyword(s):  
Ocean Circulation ◽  
North Atlantic ◽  
Ocean Color ◽  
Data Set ◽  
The North ◽  
Basin Scale ◽  
Non Linear ◽  
Color Data ◽  
The North Atlantic ◽  
Ocean Biogeochemistry

Abstract. Today, the routine assimilation of satellite data into operational models of ocean circulation is mature enough to enable the production of global reanalyses describing the ocean circulation variability during the past decades. The expansion of the "reanalysis" concept from ocean physics to biogeochemistry is a timely challenge that motivates the present study. The objective of this paper is to investigate the potential benefits of assimilating satellite-estimated chlorophyll data into a basin-scale three-dimensional coupled physical–biogeochemical model of the North Atlantic. The aim is on the one hand to improve forecasts of ocean biogeochemical properties and on the other hand to define a methodology for producing data-driven climatologies based on coupled physical–biogeochemical modeling. A simplified variant of the Kalman filter is used to assimilate ocean color data during a 9-year period. In this frame, two experiments are carried out, with and without anamorphic transformations of the state vector variables. Data assimilation efficiency is assessed with respect to the assimilated data set, nitrate of the World Ocean Atlas database and a derived climatology. Along the simulation period, the non-linear assimilation scheme clearly improves the surface analysis and forecast chlorophyll concentrations, especially in the North Atlantic bloom region. Nitrate concentration forecasts are also improved thanks to the assimilation of ocean color data while this improvement is limited to the upper layer of the water column, in agreement with recent related literature. This feature is explained by the weak correlation taken into account by the assimilation between surface phytoplankton and nitrate concentrations deeper than 50 meters. The assessment of the non-linear assimilation experiments indicates that the proposed methodology provides the skeleton of an assimilative system suitable for reanalyzing the ocean biogeochemistry based on ocean color data.

scholarly journals The Global Wind Resource Observed by Scatterometer

2020 ◽  
Vol 12 (18) ◽  
pp. 2920 ◽  
Author(s):  
Ian R. Young ◽  
Ebru Kirezci ◽  
Agustinus Ribal
Keyword(s):  
North Atlantic ◽  
Extreme Value Analysis ◽  
Data Set ◽  
Value Analysis ◽  
Wind Speeds ◽  
The North ◽  
Extreme Wind ◽  
Basin Scale ◽  
The North Atlantic ◽  
Wind Resource

A 27-year-long calibrated multi-mission scatterometer data set is used to determine the global basin-scale and near-coastal wind resource. In addition to mean and percentile values, the analysis also determines the global values of both 50- and 100-year return period wind speeds. The analysis clearly shows the seasonal variability of wind speeds and the differing response of the two hemispheres. The maximum wind speeds in each hemisphere are comparable but there is a much larger seasonal cycle in the northern hemisphere. As a result, the southern hemisphere has a more consistent year-round wind climate. Hence, coastal regions of southern Africa, southern Australia, New Zealand and southern South America appear particularly suited to coastal and offshore wind energy projects. The extreme value analysis shows that the highest extreme wind speeds occur in the North Atlantic Ocean with extreme wind regions concentrated along the western boundaries of the North Atlantic and North Pacific Oceans and the Indian Ocean sector of the Southern Ocean. The signature of tropical cyclones is clearly observed in each of the well-known tropical cyclone basins.

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