Shallow Overturning Circulations of the Tropical-Subtropical Oceans

2013 ◽  
pp. 261-304 ◽  
Author(s):  
Friedrich A. Schott ◽  
Julian P. Mccreary ◽  
Gregory C. Johnson
Keyword(s):  
Subtropical Oceans

scholarly journals Analysis of Intense Poleward Water Vapor Transports into High Latitudes of Western North America

2009 ◽  
Vol 24 (6) ◽  
pp. 1732-1747 ◽  
Author(s):  
Alain Roberge ◽  
John R. Gyakum ◽  
Eyad H. Atallah
Keyword(s):  
Water Vapor ◽  
North America ◽  
Vapor Transport ◽  
Water Vapor Transport ◽  
Western Coast ◽  
Synoptic Scale ◽  
The Pacific ◽  
The Pacific Ocean ◽  
Subtropical Oceans ◽  
Pineapple Express

Abstract Significant cool season precipitation along the western coast of North America is often associated with intense water vapor transport (IWVT) from the Pacific Ocean during favorable synoptic-scale flow regimes. These relatively narrow and intense regions of water vapor transport can originate in either the tropical or subtropical oceans, and sometimes have been referred to as Pineapple Express events in previous literature when originating near Hawaii. However, the focus of this paper will be on diagnosing the synoptic-scale signatures of all significant water vapor transport events associated with poleward moisture transport impacting the western coast of Canada, regardless of the exact points of origin of the associated atmospheric river. A trajectory analysis is used to partition the events as a means of creating coherent and meaningful synoptic-scale composites. The results indicate that these IWVT events can be clustered by the general area of origin of the majority of the saturated parcels impacting British Columbia and the Yukon Territories. IWVT events associated with more zonal trajectories are characterized by a strong and mature Aleutian low, whereas IWVT events associated with more meridional trajectories are often characterized by an anticyclone situated along the California or Oregon coastline, and a relatively mature poleward-traveling cyclone, commonly originating in the central North Pacific.

New perspectives on nitrogen-fixing microorganisms in tropical and subtropical oceans

2000 ◽  
Vol 8 (2) ◽  
pp. 68-73 ◽  
Author(s):  
Jonathan P Zehr ◽  
Edward J Carpenter ◽  
Tracy A Villareal
Keyword(s):  
Nitrogen Fixing ◽  
Subtropical Oceans

scholarly journals Modeling Photosynthesis and Exudation of DOM in Subtropical Oceans

2021 ◽  
Author(s):  
Zhen Wu ◽  
Stephanie Dutkiewicz ◽  
Oliver Jahn ◽  
Daniel Sher ◽  
Angelicque E. White ◽  
...  
Keyword(s):  
Subtropical Oceans

scholarly journals Low occurrence rates of ubiquitously present leptocephalus larvae in the stomach contents of predatory fish

2015 ◽  
Vol 72 (5) ◽  
pp. 1359-1369 ◽  
Author(s):  
Michael J. Miller ◽  
Jeff Dubosc ◽  
Elodie Vourey ◽  
Katsumi Tsukamoto ◽  
Valerie Allain
Keyword(s):  
Stomach Contents ◽  
Trophic Dynamics ◽  
Predatory Fish ◽  
Thunnus Albacares ◽  
Fish Diets ◽  
Thunnus Obesus ◽  
Leptocephalus Larvae ◽  
Subtropical Oceans ◽  
Oceanic Food Webs ◽  
Prey Items

Abstract Leptocephali, the larvae of eels, grow to large sizes and are widely distributed in tropical and subtropical oceans. Their role in oceanic food webs is poorly known because they are rarely reported as food items in fish stomach content studies. Data from 13 years of research on the trophic dynamics of Pacific Ocean predatory fish indicate that among 8746 fish of 76 species/taxa (33 families) that had been feeding, only 16 fish of 6 species had remains of 34 leptocephali in their stomachs. Only 0.013% of the 256 308 total prey items were leptocephalus larvae, and 0.03% of the total prey items were juvenile or adult eels (mostly snipe eels: Nemichthyidae). There were 10 fish of 2 species of lancetfish (Alepisaurus spp., n = 152), 2 rainbow runners (Elagatis bipinnulata, n = 222), and 2 yellowfin tuna (Thunnus albacares, n = 3103) that had leptocephali in their stomach contents, but all except one T. albacares (contained 15 leptocephali) had each eaten ≤3 leptocephali. A swallower, Pseudoscopelus sp., and a frigate tuna, Auxis thazard, had eaten single leptocephali. Twenty-eight bigeye tuna, Thunnus obesus, had eaten 76 juvenile/adult nemichthyid or serrivomerid eels. A literature survey found that only 15 out of 75 examined publications listed leptocephali in the stomach contents of a total of 6 species out of ∼ 42 300 predatory fish of 40 species. The transparency of leptocephali and their apparent mimicry of gelatinous zooplankton could contribute to lower rates of predation. Their soft bodies likely digest rapidly, so although this study and existing literature indicate that leptocephali sometimes contribute to predatory fish diets, particularly for fish that do not exclude gelatinous prey types, and fish with low digestion rates in their stomachs such as lancetfish, their levels of contribution to fish diets and the impacts of predators on eel recruitment remain uncertain.

scholarly journals Reassessing the Effect of Cloud Type on Earth’s Energy Balance in the Age of Active Spaceborne Observations. Part II: Atmospheric Heating

2019 ◽  
Vol 32 (19) ◽  
pp. 6219-6236 ◽  
Author(s):  
Yun Hang ◽  
Tristan S. L’Ecuyer ◽  
David S. Henderson ◽  
Alexander V. Matus ◽  
Zhien Wang
Keyword(s):  
Northern Hemisphere ◽  
Meridional Overturning Circulation ◽  
Regional Warming ◽  
Atmospheric Heating ◽  
Stratocumulus Clouds ◽  
Meridional Overturning ◽  
Subtropical Oceans ◽  
The Tropics ◽  
Global Mean

Abstract The role of clouds in modulating vertically integrated atmospheric heating is investigated using CloudSat’s multisensor radiative flux dataset. On the global mean, clouds are found to induce a net atmospheric heating of 0.07 ± 0.08 K day−1 that derives largely from 0.06 ± 0.07 K day−1 of enhanced shortwave absorption and a small, 0.01 ± 0.04 K day−1 reduction of longwave cooling. However, this small global average longwave effect results from the near cancellation of much larger regional warming by multilayered cloud systems in the tropics and cooling from stratocumulus clouds in subtropical oceans. Clouds are observed to warm the tropical atmosphere by 0.23 K day−1 and cool the polar atmosphere by −0.13 K day−1 enhancing required zonal heat redistribution by the meridional overturning circulation. Zonal asymmetries in the occurrence of multilayered clouds that are more frequent in the Northern Hemisphere and stratocumulus that occur more frequently over the southern oceans also leads to 3 times as much cloud heating in the Northern Hemisphere (0.1 K day−1) than the Southern Hemisphere (0.04 K day−1). These findings suggest that clouds very likely make the strongest contribution to the annual mean atmospheric energy imbalance between the hemispheres (2.0 ± 3.5 PW).

scholarly journals Contribution and pathways of diazotroph-derived nitrogen to zooplankton during the VAHINE mesocosm experiment in the oligotrophic New Caledonia lagoon

2016 ◽  
Vol 13 (10) ◽  
pp. 3131-3145 ◽  
Author(s):  
Brian P. V. Hunt ◽  
Sophie Bonnet ◽  
Hugo Berthelot ◽  
Brandon J. Conroy ◽  
Rachel A. Foster ◽  
...  
Keyword(s):  
N2 Fixation ◽  
New Caledonia ◽  
Austral Summer ◽  
Zooplankton Community ◽  
Zooplankton Biomass ◽  
Diazotrophic Cyanobacteria ◽  
Subtropical Oceans ◽  
Isotope Mixing Models

Abstract. In oligotrophic tropical and subtropical oceans, where strong stratification can limit the replenishment of surface nitrate, dinitrogen (N2) fixation by diazotrophs can represent a significant source of nitrogen (N) for primary production. The VAHINE (VAriability of vertical and tropHIc transfer of fixed N2 in the south-wEst Pacific) experiment was designed to examine the fate of diazotroph-derived nitrogen (DDN) in such ecosystems. In austral summer 2013, three large ( ∼  50 m3) in situ mesocosms were deployed for 23 days in the New Caledonia lagoon, an ecosystem that typifies the low-nutrient, low-chlorophyll environment, to stimulate diazotroph production. The zooplankton component of the study aimed to measure the incorporation of DDN into zooplankton biomass, and assess the role of direct diazotroph grazing by zooplankton as a DDN uptake pathway. Inside the mesocosms, the diatom–diazotroph association (DDA) het-1 predominated during days 5–15 while the unicellular diazotrophic cyanobacteria UCYN-C predominated during days 15–23. A Trichodesmium bloom was observed in the lagoon (outside the mesocosms) towards the end of the experiment. The zooplankton community was dominated by copepods (63 % of total abundance) for the duration of the experiment. Using two-source N isotope mixing models we estimated a mean  ∼  28 % contribution of DDN to zooplankton nitrogen biomass at the start of the experiment, indicating that the natural summer peak of N2 fixation in the lagoon was already contributing significantly to the zooplankton. Stimulation of N2 fixation in the mesocosms corresponded with a generally low-level enhancement of DDN contribution to zooplankton nitrogen biomass, but with a peak of  ∼  73 % in mesocosm 1 following the UCYN-C bloom. qPCR analysis targeting four of the common diazotroph groups present in the mesocosms (Trichodesmium, het-1, het-2, UCYN-C) demonstrated that all four were ingested by copepod grazers, and that their abundance in copepod stomachs generally corresponded with their in situ abundance. 15N2 labelled grazing experiments therefore provided evidence for direct ingestion and assimilation of UCYN-C-derived N by the zooplankton, but not for het-1 and Trichodesmium, supporting an important role of secondary pathways of DDN to the zooplankton for the latter groups, i.e. DDN contributions to the dissolved N pool and uptake by nondiazotrophs. This study appears to provide the first evidence of direct UCYN-C grazing by zooplankton, and indicates that UCYN-C-derived N contributes significantly to the zooplankton food web in the New Caledonia lagoon through a combination of direct grazing and secondary pathways.

Spatial Variability of Liquid Water Path in Marine Low Cloud: The Importance of Mesoscale Cellular Convection

2006 ◽  
Vol 19 (9) ◽  
pp. 1748-1764 ◽  
Author(s):  
Robert Wood ◽  
Dennis L. Hartmann
Keyword(s):  
Spatial Variability ◽  
Liquid Water ◽  
Large Scale ◽  
Marine Boundary Layer ◽  
Liquid Water Path ◽  
Water Path ◽  
Geographical Regions ◽  
Low Cloud ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Subtropical Oceans

Abstract Liquid water path (LWP) mesoscale spatial variability in marine low cloud over the eastern subtropical oceans is examined using two months of daytime retrievals from the Moderate Resolution Imaging Spectroradiometer (MODIS) on the NASA Terra satellite. Approximately 20 000 scenes of size 256 km × 256 km are used in the analysis. It is found that cloud fraction is strongly linked with the LWP variability in the cloudy fraction of the scene. It is shown here that in most cases LWP spatial variance is dominated by horizontal scales of 10–50 km, and increases as the variance-containing scale increases, indicating the importance of organized mesoscale cellular convection (MCC). A neural network technique is used to classify MODIS scenes by the spatial variability type (no MCC, closed MCC, open MCC, cellular but disorganized). It is shown how the different types tend to occupy distinct geographical regions and different physical regimes within the subtropics, although the results suggest considerable overlap of the large-scale meteorological conditions associated with each scene type. It is demonstrated that both the frequency of occurrence, and the variance-containing horizontal scale of the MCC increases as the marine boundary layer (MBL) depth increases. However, for the deepest MBLs, the MCC tends to be replaced by clouds containing cells but lacking organization. In regions where MCC is prevalent, a lack of sensitivity of the MCC type (open or closed) to the large-scale meteorology was found, suggesting a mechanism internal to the MBL may be important in determining MCC type. The results indicate that knowledge of the physics of MCC will be required to completely understand and predict low cloud coverage and variability in the subtropics.

Sign in / Sign up

Export Citation Format

Share Document