Horizontal advection critical for maintaining an Antarctic biological hotspot

2019 ◽  
Author(s):  
Josh Kohut ◽  
Matt Oliver ◽  
Nicole Couto ◽  
Peter Winsor ◽  
Hank Statscewich ◽  
...  
Keyword(s):  
Horizontal Advection

The Role of Oceanic Heat Advection in the Evolution of Tropical North and South Atlantic SST Anomalies*

2006 ◽  
Vol 19 (23) ◽  
pp. 6122-6138 ◽  
Author(s):  
Gregory R. Foltz ◽  
Michael J. McPhaden
Keyword(s):  
Surface Flux ◽  
South Atlantic ◽  
Shortwave Radiation ◽  
Heat Advection ◽  
Horizontal Advection ◽  
Latent Heat Loss ◽  
North And South ◽  
Sst Gradient ◽  
Sst Anomalies

Abstract The role of horizontal oceanic heat advection in the generation of tropical North and South Atlantic sea surface temperature (SST) anomalies is investigated through an analysis of the oceanic mixed layer heat balance. It is found that SST anomalies poleward of 10° are driven primarily by a combination of wind-induced latent heat loss and shortwave radiation. Away from the eastern boundary, horizontal advection damps surface flux–forced SST anomalies due to a combination of mean meridional Ekman currents acting on anomalous meridional SST gradients, and anomalous meridional currents acting on the mean meridional SST gradient. Horizontal advection is likely to have the most significant effect on the interhemispheric SST gradient mode through its impact in the 10°–20° latitude bands of each hemisphere, where the variability in advection is strongest and its negative correlation with the surface heat flux is highest. In addition to the damping effect of horizontal advection in these latitude bands, evidence for coupled wind–SST feedbacks is found, with anomalous equatorward (poleward) SST gradients contributing to enhanced (reduced) westward surface winds and an equatorward propagation of SST anomalies.

scholarly journals Interannual Variability of Sea Surface Temperature off Java and Sumatra in a Global GCM*

2008 ◽  
Vol 21 (11) ◽  
pp. 2451-2465 ◽  
Author(s):  
Yan Du ◽  
Tangdong Qu ◽  
Gary Meyers
Keyword(s):  
Indian Ocean ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Mixed Layer ◽  
Heat Budget ◽  
Sea Surface ◽  
Surface Mixed Layer ◽  
Horizontal Advection ◽  
Cold Anomaly ◽  
Sst Anomalies

Abstract Using results from the Simple Ocean Data Assimilation (SODA), this study assesses the mixed layer heat budget to identify the mechanisms that control the interannual variation of sea surface temperature (SST) off Java and Sumatra. The analysis indicates that during the positive Indian Ocean Dipole (IOD) years, cold SST anomalies are phase locked with the season cycle. They may exceed −3°C near the coast of Sumatra and extend as far westward as 80°E along the equator. The depth of the thermocline has a prominent influence on the generation and maintenance of SST anomalies. In the normal years, cooling by upwelling–entrainment is largely counterbalanced by warming due to horizontal advection. In the cooling episode of IOD events, coastal upwelling–entrainment is enhanced, and as a result of mixed layer shoaling, the barrier layer no longer exists, so that the effect of upwelling–entrainment can easily reach the surface mixed layer. Horizontal advection spreads the cold anomaly to the interior tropical Indian Ocean. Near the coast of Java, the northern branch of an anomalous anticyclonic circulation spreads the cold anomaly to the west near the equator. Both the anomalous advection and the enhanced, wind-driven upwelling generate the cold SST anomaly of the positive IOD. At the end of the cooling episode, the enhanced surface thermal forcing overbalances the cooling effect by upwelling/entrainment, and leads to a warming in SST off Java and Sumatra.

3D simulations of warm and hot Jupiter atmospheres: the role of 3D mixing in shaping CH4-to-CO conversion pathways

2021 ◽  
Author(s):  
Maria Zamyatina ◽  
Eric Hebrard ◽  
Nathan Mayne ◽  
Benjamin Drummond
Keyword(s):  
Chemical Structure ◽  
Three Dimensional ◽  
Chemical Species ◽  
Radiation Chemistry ◽  
3D Simulations ◽  
Horizontal Advection ◽  
Co Conversion ◽  
Area Of Influence ◽  
Different Parts

<p>We present results from a set of cloud-free simulations of exoplanet atmospheres using a coupled three-dimensional (3D) hydrodynamics-radiation-chemistry model. We report in particular our investigation of the thermodynamic and chemical structure of the atmospheres of HAT-P-11b and WASP-17b and their comparison with the results for the atmospheres of HD 189733b and HD 209458b presented in Drummond et al. (2020). We found that the abundances of chemical species from simulations with interactive chemistry depart from their respective abundances computed at local chemical equilibrium, especially at higher latitudes. To understand this departure, we analysed the CH<sub>4</sub>-to-CO conversion pathways within the Venot et al. (2019) reduced chemical network used in our model using a chemical network analysis. We found that at steady state nine CH<sub>4</sub>-to-CO conversion pathways manifest in our 3D simulations with interactive chemistry, with different pathways dominating different parts of the atmosphere and their area of influence being determined by the vertical and horizontal advection and shifting between planets.</p>

scholarly journals Southern Hemisphere Blocking Onsets Associated with Upper-Tropospheric Divergence Anomalies

2005 ◽  
Vol 62 (5) ◽  
pp. 1614-1625 ◽  
Author(s):  
F. Javier Sáez de Adana ◽  
Stephen J. Colucci
Keyword(s):  
Southern Hemisphere ◽  
Nonlinear Effect ◽  
Local Development ◽  
Relative Vorticity ◽  
Convective Activity ◽  
Early Winter ◽  
Horizontal Advection ◽  
Blocking Activity ◽  
The Tropics ◽  
Blocking Index

Abstract Upper-tropospheric divergence anomalies and divergence tendencies prior to and during the onset of blocking have been investigated for selected cases over the Southern Hemisphere in search of links between the upper-tropospheric response to tropical convective activity and the onset of blocking in midlatitudes. Climatologies of blocking, defined by an objective index, and divergence are established for the Southern Hemisphere and the southern Pacific, respectively. Relative blocking frequency versus longitude reveals a region of maximum blocking activity between 160°E and 75°W. Blocking frequencies for each ENSO phase indicate a shift toward the late austral fall and early winter during the warm phase, whereas during the cold and neutral phases the highest frequencies are in June and July, respectively. Composites of area-averaged divergence anomalies for the selected blocking cases reveal more anomalous divergence than during nonblocking periods over the blocking regions and the immediate upstream regions in midlatitudes. A full divergence tendency equation is utilized to diagnose the local development of divergence preceding the onset of blocking. Results indicate that divergence tendencies over midlatitudes in the block-onset region were forced primarily by horizontal advection, ageostrophic relative vorticity, and a nonlinear effect. In the region directly upstream from the block-onset region, ageostrophic relative vorticity had the greatest contribution followed by the horizontal advection. In the Tropics, divergence tendencies appear to be driven primarily by horizontal advection. Correlations of calculated divergence tendencies with the blocking index suggest that ageostrophic vorticity may locally generate divergence that in turn may force anticyclonic vorticity associated with blocking. Lag correlations with a blocking index during blocking reveal the importance of horizontal advection in driving divergence anomalies, implying divergence-induced vorticities, toward the incipient block.

Horizontal advection of temperature and salinity by Rossby waves in the North Pacific

2018 ◽  
Vol 39 (8) ◽  
pp. 2177-2188 ◽  
Author(s):  
Tatyana V. Belonenko ◽  
Igor L. Bashmachnikov ◽  
Arseny A. Kubryakov
Keyword(s):  
North Pacific ◽  
Rossby Waves ◽  
Horizontal Advection ◽  
The North ◽  
The North Pacific

Spiciness Anomalies of Subantarctic Mode Water in the South Indian Ocean

2021 ◽  
Vol 34 (10) ◽  
pp. 3927-3953
Author(s):  
Motoki Nagura
Keyword(s):  
Indian Ocean ◽  
Mixed Layer ◽  
Mixed Layer Depth ◽  
Surface Mixed Layer ◽  
The South ◽  
South Indian Ocean ◽  
Mode Water ◽  
Horizontal Advection ◽  
South Indian ◽  
Subantarctic Mode Water

AbstractThis study investigates spreading and generation of spiciness anomalies of the Subantarctic Mode Water (SAMW) located on 26.6 to 26.8 σθ in the south Indian Ocean, using in situ hydrographic observations, satellite measurements, reanalysis datasets, and numerical model output. The amplitude of spiciness anomalies is about 0.03 psu or 0.13°C and tends to be large along the streamline of the subtropical gyre, whose upstream end is the outcrop region south of Australia. The speed of spreading is comparable to that of the mean current, and it takes about a decade for a spiciness anomaly in the outcrop region to spread into the interior up to Madagascar. In the outcrop region, interannual variability in mixed layer temperature and salinity tends to be density compensating, which indicates that Eulerian temperature or salinity changes account for the generation of isopycnal spiciness anomalies. It is known that wintertime temperature and salinity in the surface mixed layer determine the temperature and salinity relationship of a subducted water mass. Considering this, the mixed layer heat budget in the outcrop region is estimated based on the concept of effective mixed layer depth, the result of which shows the primary contribution from horizontal advection. The contributions from Ekman and geostrophic currents are comparable. Ekman flow advection is caused by zonal wind stress anomalies and the resulting meridional Ekman current anomalies, as is pointed out by a previous study. Geostrophic velocity is decomposed into large-scale and mesoscale variability, both of which significantly contribute to horizontal advection.

scholarly journals Impact of Cyclonic Ocean Eddies on Upper Ocean Thermodynamic Response to Typhoon Soudelor

2019 ◽  
Vol 11 (8) ◽  
pp. 938 ◽  
Author(s):  
Jue Ning ◽  
Qing Xu ◽  
Han Zhang ◽  
Tao Wang ◽  
Kaiguo Fan
Keyword(s):  
Vertical Mixing ◽  
Heat Content ◽  
Mesoscale Eddies ◽  
Upper Ocean ◽  
Surface Cooling ◽  
Ocean Eddies ◽  
Horizontal Advection ◽  
Content Change ◽  
Order Of Magnitude ◽  
The Impact

By using multiplatform satellite datasets, Argo observations and numerical model data, the upper ocean thermodynamic responses to Super Typhoon Soudelor are investigated with a focus on the impact of an ocean cyclonic eddy (CE). In addition to the significant surface cooling inside the CE region, an abnormally large rising in subsurface temperature is observed. The maximum warming and heat content change (HCC) reach up to 4.37 °C and 1.73 GJ/m2, respectively. Moreover, the HCC is an order of magnitude larger than that calculated from statistical analysis of Argo profile data in the previous study which only considered the effects caused by typhoons. Meanwhile, the subsurface warming outside the CE is merely 1.74 °C with HCC of 0.39 GJ/m2. Previous studies suggested that typhoon-induced vertical mixing is the primary factor causing subsurface warming but these studies ignored an important mechanism related to the horizontal advection caused by the rotation and movement of mesoscale eddies. This study documents that the eddy-induced horizontal advection has a great impact on the upper ocean responses to typhoons. Therefore, the influence of eddies should be considered when studying the responses of upper ocean to typhoons with pre-existing mesoscale eddies.

scholarly journals Numerical Estimations of Horizontal Advection inside Canopies

2004 ◽  
Vol 43 (10) ◽  
pp. 1530-1538 ◽  
Author(s):  
Young-San Park ◽  
Kyaw Tha Paw U
Keyword(s):  
Eddy Diffusivity ◽  
Horizontal Distance ◽  
Universal Curve ◽  
Dimensionless Variable ◽  
Horizontal Advection ◽  
Wind Speeds ◽  
Eddy Diffusivities ◽  
Advection Diffusion Equation ◽  
Roughness Elements ◽  
Eddy Transport

Abstract Local advection of scalar quantities such as heat, moisture, or carbon dioxide occurs not only above inhomogeneous surfaces but also within roughness elements on these surfaces. A two-dimensional advection–diffusion equation is applied to examine the fractionation of scalar exchange into horizontal advection within a canopy and vertical turbulent eddy transport at the canopy top. Simulations were executed with combinations of various wind speeds, eddy diffusivities, canopy heights, and source strengths. The results show that the vertical turbulent fluxes at the canopy top increase along the fetch and approach a limit at some downstream distance. The horizontal advection in the canopy is maximum at the edge of canopy and decreases exponentially along the fetch. All cases have the same features, except the absolute quantities depend on the environmental conditions. When the horizontal axis is normalized by using the dimensionless variable xK/uh2, horizontal diffusion is negligible, and the upwind concentration profile is constant, the curves of horizontal advection and vertical flux collapse into single, unique lines, respectively (x is the horizontal distance from the canopy edge, K is the eddy diffusivity, u is the wind speed, and h is the canopy height). The ratios of horizontal advection to the vertical turbulent flux also collapse into one universal curve when plotted against the dimensionless variable xK/uh2, irrespective of source strength. The ratio R shows a power-law relation to the dimensionless distance [R = a(xK/uh2)−b, where a and b are constant].

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