scholarly journals From the chlorophyll <i>a</i> in the surface layer to its vertical profile: a Greenland Sea relationship for satellite applications

2012 ◽  
Vol 9 (6) ◽  
pp. 3567-3591
Author(s):  
A. Cherkasheva ◽  
A. Bracher ◽  
E.-M. Nöthig ◽  
E. Bauerfeind ◽  
C. Melsheimer
Keyword(s):  
Surface Layer ◽  
Primary Production ◽  
Vertical Profile ◽  
Chlorophyll Concentration ◽  
Surface Concentration ◽  
The Arctic ◽  
Greenland Sea ◽  
Arctic Regions ◽  
Production Models

Abstract. Current estimates of global marine primary production range over a factor of two. At high latitudes, the uncertainty is even larger than globally because here in-situ data and ocean color observations are scarce, and the phytoplankton absorption shows specific characteristics due to the low-light adaptation. The improvement of the primary production estimates requires an accurate knowledge on the chlorophyll vertical profile, which is the basis for most primary production models. To date, studies describing the typical chlorophyll profile based on the chlorophyll in the surface layer did not include the Arctic region or, if it was included, the dependence of the profile shape on surface concentration was neglected. The goal of our study was to derive and describe the typical Greenland Sea chlorophyll profiles, categorized according to the chlorophyll concentration in the surface layer and further monthly resolved. The Greenland Sea was chosen because it is known to be one of the most productive regions of the Arctic and is among the Arctic regions where most chlorophyll field data are available. Our database contained 1199 chlorophyll profiles from R/Vs Polarstern and Maria S Merian cruises combined with data of the ARCSS-PP database (Arctic primary production in-situ database) for the years 1957–2010. The profiles were categorized according to their mean concentration in the surface layer and then monthly median profiles within each category were calculated. The category with the surface layer chlorophyll exceeding 0.7 mg C m−3 showed a clear seasonal cycle with values gradually decreasing from April to August. Chlorophyll profiles maxima moved from lower depths in spring towards the surface in late summer. Profiles with smallest surface values always showed a subsurface chlorophyll maximum with its median magnitude reaching up to three times the surface concentration. While the variability in April, May and June of the Greenland Sea season is following the global non-monthly resolved relationship of the chlorophyll profile to surface chlorophyll concentrations described by the model of Morel and Berthon (1989), it deviates significantly from that in other months (July–September) where the maxima of the chlorophyll are at quite different depths. The Greenland Sea dimensionless monthly median profiles intersect roughly at one common depth within each category. Finally, by applying a Gaussian fitting with 0.1 mg C m−3 surface chlorophyll steps to the median monthly resolved chlorophyll profiles of the defined categories, mathematical approximations have been determined. These will be used as the input to the satellite-based primary production models estimating primary production in Arctic regions.

scholarly journals From the chlorophyll <i>a</i> in the surface layer to its vertical profile: a Greenland Sea relationship for satellite applications

Ocean Science ◽  
2013 ◽  
Vol 9 (2) ◽  
pp. 431-445 ◽  
Author(s):  
A. Cherkasheva ◽  
E.-M. Nöthig ◽  
E. Bauerfeind ◽  
C. Melsheimer ◽  
A. Bracher
Keyword(s):  
Surface Layer ◽  
Primary Production ◽  
Light Adaptation ◽  
Seasonal Pattern ◽  
Chlorophyll Concentration ◽  
Surface Concentration ◽  
The Arctic ◽  
Greenland Sea ◽  
Production Models

Abstract. Current estimates of global marine primary production range over a factor of two. Improving these estimates requires an accurate knowledge of the chlorophyll vertical profiles, since they are the basis for most primary production models. At high latitudes, the uncertainty in primary production estimates is larger than globally, because here phytoplankton absorption shows specific characteristics due to the low-light adaptation, and in situ data and ocean colour observations are scarce. To date, studies describing the typical chlorophyll profile based on the chlorophyll in the surface layer have not included the Arctic region, or, if it was included, the dependence of the profile shape on surface concentration was neglected. The goal of our study was to derive and describe the typical Greenland Sea chlorophyll profiles, categorized according to the chlorophyll concentration in the surface layer and further monthly resolved profiles. The Greenland Sea was chosen because it is known to be one of the most productive regions of the Arctic and is among the regions in the Arctic where most chlorophyll field data are available. Our database contained 1199 chlorophyll profiles from R/Vs Polarstern and Maria S. Merian cruises combined with data from the ARCSS-PP database (Arctic primary production in situ database) for the years 1957–2010. The profiles were categorized according to their mean concentration in the surface layer, and then monthly median profiles within each category were calculated. The category with the surface layer chlorophyll (CHL) exceeding 0.7 mg C m−3 showed values gradually decreasing from April to August. A similar seasonal pattern was observed when monthly profiles were averaged over all the surface CHL concentrations. The maxima of all chlorophyll profiles moved from the greater depths to the surface from spring to late summer respectively. The profiles with the smallest surface values always showed a subsurface chlorophyll maximum with its median magnitude reaching up to three times the surface concentration. While the variability of the Greenland Sea season in April, May and June followed the global non-monthly resolved relationship of the chlorophyll profile to surface chlorophyll concentrations described by the model of Morel and Berthon (1989), it deviated significantly from the model in the other months (July–September), when the maxima of the chlorophyll are at quite different depths. The Greenland Sea dimensionless monthly median profiles intersected roughly at one common depth within each category. By applying a Gaussian fit with 0.1 mg C m−3 surface chlorophyll steps to the median monthly resolved chlorophyll profiles of the defined categories, mathematical approximations were determined. They generally reproduce the magnitude and position of the CHL maximum, resulting in an average 4% underestimation in Ctot (and 2% in rough primary production estimates) when compared to in situ estimates. These mathematical approximations can be used as the input to the satellite-based primary production models that estimate primary production in the Arctic regions.

Synthesis of integrated primary production in the Arctic Ocean: II. In situ and remotely sensed estimates

2013 ◽  
Vol 110 ◽  
pp. 107-125 ◽  
Author(s):  
Victoria J. Hill ◽  
Patricia A. Matrai ◽  
Elise Olson ◽  
S. Suttles ◽  
Mike Steele ◽  
...  
Keyword(s):  
Primary Production ◽  
Arctic Ocean ◽  
Remotely Sensed ◽  
The Arctic ◽  
The Arctic Ocean

scholarly journals Seven Years of SMOS Sea Surface Salinity at High Latitudes: Variability in Arctic and Sub-Arctic Regions

2018 ◽  
Vol 10 (11) ◽  
pp. 1772 ◽  
Author(s):  
Estrella Olmedo ◽  
Carolina Gabarró ◽  
Verónica González-Gambau ◽  
Justino Martínez ◽  
Joaquim Ballabrera-Poy ◽  
...  
Keyword(s):  
Dynamic Range ◽  
Remotely Sensed ◽  
Sea Surface ◽  
Sea Surface Salinity ◽  
The Arctic ◽  
Surface Salinity ◽  
In Situ Data ◽  
Arctic Regions ◽  
The Difference

This paper aims to present and assess the quality of seven years (2011–2017) of 25 km nine-day Soil Moisture and Ocean Salinity (SMOS) Sea Surface Salinity (SSS) objectively analyzed maps in the Arctic and sub-Arctic oceans ( 50 ∘ N– 90 ∘ N). The SMOS SSS maps presented in this work are an improved version of the preliminary three-year dataset generated and freely distributed by the Barcelona Expert Center. In this new version, a time-dependent bias correction has been applied to mitigate the seasonal bias that affected the previous SSS maps. An extensive database of in situ data (Argo floats and thermosalinograph measurements) has been used for assessing the accuracy of this product. The standard deviation of the difference between the new SMOS SSS maps and Argo SSS ranges from 0.25 and 0.35. The major features of the inter-annual SSS variations observed by the thermosalinographs are also captured by the SMOS SSS maps. However, the validation in some regions of the Arctic Ocean has not been feasible because of the lack of in situ data. In those regions, qualitative comparisons with SSS provided by models and the remotely sensed SSS provided by Aquarius and SMAP have been performed. Despite the differences between SMOS and SMAP, both datasets show consistent SSS variations with respect to the model and the river discharge in situ data, but present a larger dynamic range than that of the model. This result suggests that, in those regions, the use of the remotely sensed SSS may help to improve the models.

Remotely sensed primary production in the western Ross Sea: results of in situ tuned models

2003 ◽  
Vol 15 (1) ◽  
pp. 77-84 ◽  
Author(s):  
R. BARBINI ◽  
F. COLAO ◽  
R. FANTONI ◽  
L. FIORANI ◽  
A. PALUCCI ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Primary Production ◽  
Ross Sea ◽  
Wide Field ◽  
Production Models ◽  
Wide Field Of View ◽  
And Performance ◽  
The Antarctic ◽  
Global Carbon

The Southern Ocean plays an important role in the global carbon cycle and, as a consequence, in the planetary climate equilibrium. The Ross Sea is one of the more productive regions in the Southern Ocean, due to strong phytoplankton blooms occurring during summer. Satellite remote sensing is a powerful tool for investigating such phenomena, especially if the bio-optical algorithms are tuned with in situ data. In this paper, after having compared the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) and the ENEA Lidar Fluorosensor (ELF), the SeaWiFS chlorophyll a (Chl a) algorithm is tuned in the Ross Sea by means of the ELF measurements. The Chl a concentrations obtained in this way have been the basis for estimating productivity values and their evolution during summer 1997–98. Three primary production models have been used, providing information on their accuracy and performance in the Antarctic environment. Our investigations suggest that the primary production was lower than usual during the period 3 December 1997–16 January 1998.

scholarly journals Synoptic evaluation of carbon cycling in Beaufort Sea during summer: contrasting river inputs, ecosystem metabolism and air–sea CO<sub>2</sub> fluxes

2013 ◽  
Vol 10 (10) ◽  
pp. 15641-15710
Author(s):  
A. Forest ◽  
P. Coupel ◽  
B. Else ◽  
S. Nahavandian ◽  
B. Lansard ◽  
...  
Keyword(s):  
Surface Layer ◽  
Organic Carbon ◽  
Sea Ice ◽  
Primary Production ◽  
Arctic Ocean ◽  
Carbon Cycling ◽  
Shelf Break ◽  
The Arctic ◽  
Community Respiration ◽  
Co2 Fluxes

Abstract. The accelerated decline in Arctic sea ice combined with an ongoing trend toward a more dynamic atmosphere is modifying carbon cycling in the Arctic Ocean. A critical issue is to understand how net community production (NCP; the balance between gross primary production and community respiration) responds to changes and modulates air–sea CO2 fluxes. Using data collected as part of the ArcticNet-Malina 2009 expedition in southeastern Beaufort Sea (Arctic Ocean), we synthesize information on sea ice, wind, river, water column properties, metabolism of the planktonic food web, organic carbon fluxes and pools, as well as air–sea CO2 exchange, with the aim of identifying indices of ecosystem response to environmental changes. Data were analyzed to develop a non-steady-state carbon budget and an assessment of NCP against air–sea CO2 fluxes. The mean atmospheric forcing was a mild upwelling-favorable wind (~5 km h−1) blowing from the N-E and a decaying ice cover (<80% concentration) was observed beyond the shelf, the latter being fully exposed to the atmosphere. We detected some areas where the surface mixed layer was net autotrophic owing to high rates of primary production (PP), but the ecosystem was overall net heterotrophic. The region acted nonetheless as a sink for atmospheric CO2 with a mean uptake rate of −2.0 ± 3.3 mmol C m−2d−1. We attribute this discrepancy to: (1) elevated PP rates (>600 mg C m−2d−1) over the shelf prior to our survey, (2) freshwater dilution by river runoff and ice melt, and (3) the presence of cold surface waters offshore. Only the Mackenzie River delta and localized shelf areas directly affected by upwelling were identified as substantial sources of CO2 to the atmosphere (>10mmol C m−2d−1). Although generally <100 mg C m−2d−1, daily PP rates cumulated to a total PP of ~437.6 × 103 t C, which was roughly twice higher than the organic carbon delivery by river inputs (~241.2 × 103 t C). Subsurface PP represented 37.4% of total PP for the whole area and as much as ~72.0% seaward of the shelf break. In the upper 100 m, bacteria dominated (54%) total community respiration (~250 mg C m−2d−1), whereas protozoans, metazoans, and benthos, contributed to 24%, 10%, and 12%, respectively. The range of production-to-biomass ratios of bacteria was wide (1–27% d−1), while we estimated a narrower range for protozoans (6–11% d−1) and metazoans (1–3 % d−1). Over the shelf, benthic biomass was twice higher (~5.9 g C m−2) than the biomass of pelagic heterotrophs (~2.4 g C m−2), in accord with high vertical carbon fluxes on the shelf (956 ± 129 mg C m−2d−1). Threshold PP (PP at which NCP becomes positive) in the surface layer oscillated from 20–152 mg C m−2d−1, with a pattern from low-to-high values as the distance from the Mackenzie River decreased. We conclude that: (1) climate change is exacerbating the already extreme biological gradient across the Arctic shelf-basin system; (2) the Mackenzie Shelf acts as a weak sink for atmospheric CO2, implying that PP exceeds the respiration of terrigenous and marine organic matter in the surface layer; and (3) shelf break upwelling can transfer CO2 to the atmosphere, but massive outgassing can be attenuated if nutrients brought also by upwelling support diatom production. Our study underscores that cross-shelf exchange of waters, nutrients and particles is a key mechanism that needs to be properly monitored as the Arctic transits to a new state.

Relations of phytoplankton in situ primary production, chlorophyll concentration and underwater irradiance in turbid lakes

Hydrobiologia ◽  
2008 ◽  
Vol 599 (1) ◽  
pp. 169-176 ◽  
Author(s):  
Helgi Arst ◽  
Tiina Nõges ◽  
Peeter Nõges ◽  
Birgot Paavel
Keyword(s):  
Primary Production ◽  
Chlorophyll Concentration ◽  
Underwater Irradiance

scholarly journals Synoptic evaluation of carbon cycling in the Beaufort Sea during summer: contrasting river inputs, ecosystem metabolism and air–sea CO<sub>2</sub> fluxes

2014 ◽  
Vol 11 (10) ◽  
pp. 2827-2856 ◽  
Author(s):  
A. Forest ◽  
P. Coupel ◽  
B. Else ◽  
S. Nahavandian ◽  
B. Lansard ◽  
...  
Keyword(s):  
Surface Layer ◽  
Organic Carbon ◽  
Sea Ice ◽  
Primary Production ◽  
Arctic Ocean ◽  
Carbon Cycling ◽  
Shelf Break ◽  
The Arctic ◽  
Community Respiration ◽  
Co2 Fluxes

Abstract. The accelerated decline in Arctic sea ice and an ongoing trend toward more energetic atmospheric and oceanic forcings are modifying carbon cycling in the Arctic Ocean. A critical issue is to understand how net community production (NCP; the balance between gross primary production and community respiration) responds to changes and modulates air–sea CO2 fluxes. Using data collected as part of the ArcticNet–Malina 2009 expedition in the southeastern Beaufort Sea (Arctic Ocean), we synthesize information on sea ice, wind, river, water column properties, metabolism of the planktonic food web, organic carbon fluxes and pools, as well as air–sea CO2 exchange, with the aim of documenting the ecosystem response to environmental changes. Data were analyzed to develop a non-steady-state carbon budget and an assessment of NCP against air–sea CO2 fluxes. During the field campaign, the mean wind field was a mild upwelling-favorable wind (~ 5 km h−1) from the NE. A decaying ice cover (< 80% concentration) was observed beyond the shelf, the latter being fully exposed to the atmosphere. We detected some areas where the surface mixed layer was net autotrophic owing to high rates of primary production (PP), but the ecosystem was overall net heterotrophic. The region acted nonetheless as a sink for atmospheric CO2, with an uptake rate of −2.0 ± 3.3 mmol C m−2 d−1 (mean ± standard deviation associated with spatial variability). We attribute this discrepancy to (1) elevated PP rates (> 600 mg C m−2 d−1) over the shelf prior to our survey, (2) freshwater dilution by river runoff and ice melt, and (3) the presence of cold surface waters offshore. Only the Mackenzie River delta and localized shelf areas directly affected by upwelling were identified as substantial sources of CO2 to the atmosphere (> 10 mmol C m−2 d−1). Daily PP rates were generally < 100 mg C m−2 d−1 and cumulated to a total PP of ~ 437.6 × 103 t C for the region over a 35-day period. This amount was about twice the organic carbon delivery by river inputs (~ 241.2 × 103 t C). Subsurface PP represented 37.4% of total PP for the whole area and as much as ~ 72.0% seaward of the shelf break. In the upper 100 m, bacteria dominated (54%) total community respiration (~ 250 mg C m−2 d−1), whereas protozoans, metazoans, and benthos, contributed to 24, 10, and 12%, respectively. The range of production-to-biomass ratios of bacteria was wide (1–27% d−1), while we estimated a narrower range for protozoans (6–11% d−1) and metazoans (1–3% d−1). Over the shelf, benthic biomass was twofold (~ 5.9 g C m−2) the biomass of pelagic heterotrophs (~ 2.4 g C m−2), in accord with high vertical carbon fluxes on the shelf (956 ± 129 mg C m−2 d−1). Threshold PP (PP at which NCP becomes positive) in the surface layer oscillated from 20 to 152 mg C m−2 d−1, with a pattern from low-to-high values as the distance from the Mackenzie River decreased. We conclude that (1) climate change is exacerbating the already extreme biological gradient across the Beaufort shelf–basin system; (2) the Mackenzie Shelf acts as a weak sink for atmospheric CO2, suggesting that PP might exceed the respiration of terrigenous and marine organic matter in the surface layer; and (3) shelf break upwelling can transfer CO2 to the atmosphere, but CO2 outgassing can be attenuated if nutrients brought also by upwelling support diatom production. Our study underscores that cross-shelf exchange of waters, nutrients and particles is a key mechanism that needs to be properly monitored as the Arctic transits to a new state.

Pedogenic Zonation in the Well-Drained Soils of the Arctic Regions

1986 ◽  
Vol 26 (1) ◽  
pp. 100-120 ◽  
Author(s):  
Fiorenzo C. Ugolini
Keyword(s):  
Arctic Region ◽  
The Arctic ◽  
Polar Regions ◽  
Arctic Regions ◽  
Arctic Alaska ◽  
Latitudinal Transect ◽  
Conjugate Bases ◽  
Pedogenic Processes ◽  
First Time

Pedogenic zonation in the soils of the polar regions is a result of gradients in environmental factors and attendant chemical processes. Along a latitudinal transect, it is best manifested at well-drained sites and by soils developed on predominantly silicate rocks. Selected sites in arctic Alaska, in the Canadian arctic, Greenland, and Svalbard adequately fulfill these prerequisites. The processes of podzolization, decarbonization-carbonization, pervection, and salinization as models of arctic pedogenesis demonstrate that processes occurring in the temperate region also operate in the Far North. Brunification, melanization, and oxidation are recognized for the first time as current geochemical and pedogenic mechanisms of the Arctic region. Traditional genetic soil names have been retained because they represent a closer relationship to pedogenic processes than the more modern nomenclature. The identification, the chemical behavior, the strength, abundance, and mobility of the proton donors and conjugate bases are keys to the genesis of soils and the distinction of contrasting soil processes. This new approach to the understanding of arctic pedogenesis can be better fulfilled by collecting, analyzing, and interpreting soil solution obtained in situ.

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