scholarly journals An open ocean region in Neoproterozoic glaciations would have to be narrow to allow equatorial ice sheets

2013 ◽  
Vol 40 (20) ◽  
pp. 5503-5507 ◽  
Author(s):  
Christian B. Rodehacke ◽  
Aiko Voigt ◽  
Florian Ziemen ◽  
Dorian S. Abbot
Keyword(s):  
Ice Sheets ◽  
Open Ocean ◽  
Ocean Region ◽  
Neoproterozoic Glaciations

scholarly journals Variation of Summer Oceanic <i>p</i>CO<sub>2</sub> and Carbon Sink in the Prydz Bay Using SOM Analysis Approach

2018 ◽  
Author(s):  
Suqing Xu ◽  
Keyhong Park ◽  
Yanmin Wang ◽  
Liqi Chen ◽  
Qi Di ◽  
...  
Keyword(s):  
Sea Ice ◽  
Open Ocean ◽  
Sea Surface ◽  
Biological Factor ◽  
Prydz Bay ◽  
Co2 Uptake ◽  
Ocean Region ◽  
Co2 Sink ◽  
Shelf Region

Abstract. This study applies a neural network technique to produce maps of oceanic surface pCO2 in the Prydz Bay in the Southern Ocean on a 0.1 longitude × 0.1 latitude grid based on in-situ measurements during the 31th CHINARE cruise for February 2015. The study area was divided into three regions, Open-ocean region, Sea-ice region and Shelf region. The distribution of oceanic pCO2 was mainly affected by physical process in the Open-ocean region where mixing and upwelling became the main controls. While in the Sea-ice region, oceanic pCO2 changed sharply due to the strong change of seasonal ice. For the Shelf region, biological factor was the main control. The weekly oceanic pCO2 was estimated using a self-organizing map (SOM) by four proxy parameters (Sea Surface Temperature, Chlorophyll a concentration, Mixed Layer Depth, and Sea Surface Salinity) to resolve the nonlinear relationships under complicated biogeochemical conditions in Prydz Bay region. The reconstructed oceanic pCO2 coincides well with the in-situ investigated pCO2 from SOCAT, in the root-mean-square error of 22.14 μatm. Prydz Bay was mainly a strong CO2 sink in February 2015 with a monthly averaged uptake of 18.7 &amp;pm; 4.93 TgC. The oceanic CO2 sink is pronounced in the Shelf region due to its lowest oceanic pCO2 with peak biological production. Strong potential anthropogenic CO2 uptake in the Shelf region will enhance the acidification in the deep water of Prydz Bay and affect the deep ocean acidification in the long run since it contributes to the formation of Antarctic bottom water.

scholarly journals Variations in the summer oceanic <i>p</i>CO<sub>2</sub> and carbon sink in Prydz Bay using the self-organizing map analysis approach

2019 ◽  
Vol 16 (3) ◽  
pp. 797-810 ◽  
Author(s):  
Suqing Xu ◽  
Keyhong Park ◽  
Yanmin Wang ◽  
Liqi Chen ◽  
Di Qi ◽  
...  
Keyword(s):  
Sea Ice ◽  
Open Ocean ◽  
Sea Surface ◽  
Prydz Bay ◽  
Self Organizing Map ◽  
Ocean Region ◽  
Co2 Sink ◽  
Shelf Region ◽  
Self Organizing

Abstract. This study applies a neural network technique to produce maps of oceanic surface pCO2 in Prydz Bay in the Southern Ocean on a weekly 0.1∘ longitude × 0.1∘ latitude grid based on in situ measurements obtained during the 31st CHINARE cruise from February to early March 2015. This study area was divided into three regions, namely, the “open-ocean” region, “sea-ice” region and “shelf” region. The distribution of oceanic pCO2 was mainly affected by physical processes in the open-ocean region, where mixing and upwelling were the main controls. In the sea-ice region, oceanic pCO2 changed sharply due to the strong change in seasonal ice. In the shelf region, biological factors were the main control. The weekly oceanic pCO2 was estimated using a self-organizing map (SOM) with four proxy parameters (sea surface temperature, chlorophyll a concentration, mixed Layer Depth and sea surface salinity) to overcome the complex relationship between the biogeochemical and physical conditions in the Prydz Bay region. The reconstructed oceanic pCO2 data coincide well with the in situ pCO2 data from SOCAT, with a root mean square error of 22.14 µatm. Prydz Bay was mainly a strong CO2 sink in February 2015, with a monthly averaged uptake of 23.57±6.36 TgC. The oceanic CO2 sink is pronounced in the shelf region due to its low oceanic pCO2 values and peak biological production.

scholarly journals The Vertical Structure of Open-Ocean Submesoscale Variability during a Full Seasonal Cycle

2020 ◽  
Vol 50 (1) ◽  
pp. 145-160 ◽  
Author(s):  
Zachary K. Erickson ◽  
Andrew F. Thompson ◽  
Jörn Callies ◽  
Xiaolong Yu ◽  
Alberto Naveira Garabato ◽  
...  
Keyword(s):  
Structure Function ◽  
Mixed Layer ◽  
Seasonal Cycle ◽  
Spatial Scales ◽  
Horizontal Resolution ◽  
Ocean Model ◽  
Open Ocean ◽  
Order Structure ◽  
Numerical Ocean Model ◽  
Ocean Region

AbstractSubmesoscale dynamics are typically intensified at boundaries and assumed to weaken below the mixed layer in the open ocean. Here, we assess both the seasonality and the vertical distribution of submesoscale motions in an open-ocean region of the northeast Atlantic. Second-order structure functions, or variance in properties separated by distance, are calculated from submesoscale-resolving ocean glider and mooring observations, as well as a 1/48° numerical ocean model. This dataset combines a temporal coverage that extends through a full seasonal cycle, a horizontal resolution that captures spatial scales as small as 1 km, and vertical sampling that provides near-continuous coverage over the upper 1000 m. While kinetic and potential energies undergo a seasonal cycle, being largest during the winter, structure function slopes, influenced by dynamical characteristics, do not exhibit a strong seasonality. Furthermore, structure function slopes show weak vertical variations; there is not a strong change in properties across the base of the mixed layer. Additionally, we compare the observations to output from a high-resolution numerical model. The model does not represent variability associated with superinertial motions and does not capture an observed reduction in submesoscale kinetic energy that occurs throughout the water column in spring. Overall, these results suggest that the transfer of mixed layer submesoscale variability down to depths below the traditionally defined mixed layer is important throughout the weakly stratified subpolar mode waters.

Drivers of diversity gradients of a highly mobile marine assemblage in a mesoscale seascape

2020 ◽  
Vol 638 ◽  
pp. 149-164
Author(s):  
GM Svendsen ◽  
M Ocampo Reinaldo ◽  
MA Romero ◽  
G Williams ◽  
A Magurran ◽  
...  
Keyword(s):  
Environmental Gradients ◽  
Regression Tree ◽  
Demersal Fish ◽  
Open Ocean ◽  
Shared Resources ◽  
Thermal Front ◽  
Boosted Regression Tree ◽  
Diversity Gradients ◽  
Α Diversity ◽  
Bottom Depth

With the unprecedented rate of biodiversity change in the world today, understanding how diversity gradients are maintained at mesoscales is a key challenge. Drawing on information provided by 3 comprehensive fishery surveys (conducted in different years but in the same season and with the same sampling design), we used boosted regression tree (BRT) models in order to relate spatial patterns of α-diversity in a demersal fish assemblage to environmental variables in the San Matias Gulf (Patagonia, Argentina). We found that, over a 4 yr period, persistent diversity gradients of species richness and probability of an interspecific encounter (PIE) were shaped by 3 main environmental gradients: bottom depth, connectivity with the open ocean, and proximity to a thermal front. The 2 main patterns we observed were: a monotonic increase in PIE with proximity to fronts, which had a stronger effect at greater depths; and an increase in PIE when closer to the open ocean (a ‘bay effect’ pattern). The originality of this work resides on the identification of high-resolution gradients in local, demersal assemblages driven by static and dynamic environmental gradients in a mesoscale seascape. The maintenance of environmental gradients, specifically those associated with shared resources and connectivity with an open system, may be key to understanding community stability.

A topological approach to the strain-rate pattern of ice sheets

1993 ◽  
Vol 39 (131) ◽  
pp. 10-14 ◽  
Author(s):  
J. F. Nye
Keyword(s):  
Strain Rate ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Point Of View ◽  
Principal Strain ◽  
Topological Approach ◽  
Contour Maps ◽  
Isotropic Point ◽  
Horizontal Strain

AbstractThe pattern of horizontal strain rate in an ice sheet is discussed from a topological point of view. In a circularly symmetric ice sheet, the isotropic point for strain rate at its centre is degenerate and structurally unstable. On perturbation the degenerate point splits into two elementary isotropic points, each of which has the lemon pattern for the trajectories of principal strain rate. Contour maps of principal strain-rate values are presented which show the details of the splitting.

Analysis and Simulation of Altimeter Performance for the Production of Ice Sheet Topographic Maps

1986 ◽  
Vol 8 ◽  
pp. 141-145 ◽  
Author(s):  
K.C. Partington ◽  
C.G. Rapley
Keyword(s):  
High Precision ◽  
Systems Analysis ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Data Interpretation ◽  
Topographic Maps ◽  
Error Signal ◽  
Tracking Systems ◽  
Tracking Mode ◽  
Non Linear

Satellite-borne, radar altimeters have already demonstrated an ability to produce high-precision, topographic maps of the ice sheets. Seasat operated in a tracking mode, designed for use over oceans, but successfully tracked much of the flatter regions of the ice sheet to ± 72° latitude. ERS-1 will extend coverage to ± 82° latitude and will be equipped with an ocean mode similar to that of Seasat and an ice mode designed to permit tracking of the steeper, peripheral regions. The ocean mode will be used over the flatter regions, because of its greater precision.Altimeter performance over the ice sheets has been investigated through a study of Seasat tracking behaviour and the use of an altimeter performance simulator, with a view to assessing the likely performance of ERS-1 and the design of improved tracking systems. Analysis of Seasat data shows that lock was frequently lost, as a result of possessing a non-linear height error signal over the width of the range window. Having lost lock, the tracker frequently failed to transfer rapidly and effectively to track mode. Use of the altimeter performance simulator confirms many of the findings from Seasat data and it is being used to facilitate data interpretation and mapping, through the modelling of waveform sequence.

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