scholarly journals Influence of Global Warming on Baroclinic Rossby Radius in the Ocean: A Model Intercomparison

2006 ◽  
Vol 19 (7) ◽  
pp. 1354-1360 ◽  
Author(s):  
Oleg A. Saenko
Keyword(s):  
General Circulation ◽  
Large Scale ◽  
Rossby Waves ◽  
Co2 Concentration ◽  
General Circulation Models ◽  
Atmospheric Co2 ◽  
Western Boundary ◽  
Boundary Currents ◽  
Atmospheric Co2 Concentration ◽  
Rossby Radius Of Deformation

Abstract Results from eight ocean–atmosphere general circulation models are used to evaluate the influence of the projected changes in the oceanic stratification on the first baroclinic Rossby radius of deformation in the ocean, associated with atmospheric CO2 increase. For each of the models, an oceanic state corresponding to the A1B stabilization experiment (with atmospheric CO2 concentration of 720 ppm) is compared to a state corresponding to the preindustrial control experiment (with atmospheric CO2 concentration of 280 ppm). In all of the models, the first baroclinic Rossby radius increases with increasing oceanic stratification in the warmer climate. There is, however, a considerable range among the models in the magnitude of the increase. At the latitudes of intense eddy activity associated with instability of western boundary currents (around 35°–40°), the increase reaches 4 km on average, or about 15% of the local baroclinic Rossby radius. Some of the models predict an increase of the baroclinic Rossby radius by more than 20% at these latitudes under the applied forcing. It is therefore suggested that in a plausible future warmer climate, the characteristic length scale of mesoscale eddies, as well as boundary currents and fronts, may increase. In addition, since the speed of long baroclinic Rossby waves is proportional to the squared baroclinic Rossby radius of deformation, the results suggest that the time scale for large-scale dynamical oceanic adjustment may decrease in the warmer climate, thereby increasing the frequency of long-term climate variability where the oceanic Rossby wave dynamics set the dominant period. Finally, the speed of equatorial Kelvin waves and Rossby waves, carrying signals along the equator, including those related to ENSO, is projected to increase.

scholarly journals Climate and Ocean Circulation in the Aftermath of a Marinoan Snowball Earth

2021 ◽  
Author(s):  
Lennart Ramme ◽  
Jochem Marotzke
Keyword(s):  
Ocean Circulation ◽  
General Circulation ◽  
Three Dimensional ◽  
Circulation Model ◽  
Co2 Concentration ◽  
Ocean General Circulation Model ◽  
Atmospheric Co2 ◽  
Snowball Earth ◽  
Freshwater Environment ◽  
Atmospheric Co2 Concentration

Abstract. When a snowball Earth deglaciates through a very high atmospheric CO2 concentration, the resulting inflow of freshwater leads to a stably stratified ocean, and the strong greenhouse conditions drive the climate into a very warm state. Here, we use a coupled atmosphere-ocean general circulation model, applying different scenarios for the evolution of atmospheric CO2, to conduct the first simulation of the climate and the three-dimensional ocean circulation in the aftermath of the Marinoan snowball Earth. The simulations show that the strong freshwater stratification breaks up on a timescale in the order of 103 years, mostly independent of the applied CO2 scenario. This is driven by the upwelling of salty waters in high latitudes, mainly the northern hemisphere, where a strong circumpolar current dominates the circulation. In the warmest CO2 scenario, the simulated Marinoan supergreenhouse climate reaches a global mean surface temperature of about 30 °C under an atmospheric CO2 concentration of 15 × 103 parts per million by volume, which is a moderate temperature compared to previous estimates. Consequently, the thermal expansion of seawater causes a sea-level rise of only 8 m, with most of it occurring during the first 3000 years. Our results imply that the surface temperatures of that time were potentially not as threatening for early metazoa as previously assumed. Furthermore, the short destratification timescale found in this study implies a very rapid accumulation of Marinoan cap dolostones, given that they were deposited in a freshwater environment.

scholarly journals A comparative study of large scale atmospheric circulation in the context of future scenario (RCP4.5) and past warmth (Mid Pliocene)

2013 ◽  
Vol 9 (2) ◽  
pp. 1449-1483
Author(s):  
Y. Sun ◽  
G. Ramstein ◽  
C. Contoux ◽  
T. Zhou
Keyword(s):  
Large Scale ◽  
Co2 Concentration ◽  
Future Climate ◽  
Hadley Cell ◽  
Atmospheric Co2 ◽  
Future Scenario ◽  
Atmospheric Co2 Concentration ◽  
Walker Cell ◽  
Tropical Areas ◽  
Modern Level

Abstract. The Pliocene climate (3.3 ~ 3.0 Ma) is often considered as the last sustained warm period with close enough geographic configurations compared to the present one and associated with atmospheric CO2 concentration (405 ± 50 ppm) higher than the modern level. It is therefore suggested that the warm Pliocene climate may provide a plausible scenario for the future climate warming with the important advantage, that for mid-Pliocene, many marine and continental data are available. To investigate this issue, we selected RCP4.5 scenario, one of the current available future projections, to compare the pattern of tropical atmospheric response with past warm mid-Pliocene climate. We performed three OAGCM simulations (RCP4.5 scenario, mid-Pliocene and present day simulation) with the IPSL-CM5A model and investigated atmospheric tropical dynamics through Hadley and Walker cell responses to warmer conditions. Our results show that there is a damping of the Hadley cell intensity in the northern tropics and an increase in both subtropics. Moreover, northern and southern Hadley cells expand poleward. The response of Hadley cell is stronger for RCP4.5 scenario than for mid-Pliocene, but in very good agreement with the fact the atmospheric CO2 concentration is higher in future scenario than mid-Pliocene (543 versus 405 ppm). Concerning the response of the Walker cell, we showed that, despite very large similarities, there are also some differences. i.e. the common features are for both scenarios: weakening of the ascending branch, leading to a suppression of the precipitation over the western tropical Pacific. The response of Walker cell is stronger in RCP4.5 scenario than mid-Pliocene but also depicts some major difference as an eastward shift of the rising branch of Walker cell in future scenario compared to the mid-Pliocene. In this paper, we explain the dynamics of the Hadley and Walker cell, and show that despite minor discrepancy, mid-Pliocene is certainly an interesting analogue for future climate changes in the tropical areas.

scholarly journals Response of simulated burned area to historical changes in environmental and anthropogenic factors: a comparison of seven fire models

2019 ◽  
Vol 16 (19) ◽  
pp. 3883-3910 ◽  
Author(s):  
Lina Teckentrup ◽  
Sandy P. Harrison ◽  
Stijn Hantson ◽  
Angelika Heil ◽  
Joe R. Melton ◽  
...  
Keyword(s):  
Land Use ◽  
Co2 Concentration ◽  
Fire Regimes ◽  
Atmospheric Co2 ◽  
Anthropogenic Factors ◽  
Burned Area ◽  
Earth System ◽  
Atmospheric Co2 Concentration ◽  
Fire Models ◽  
The Impact

Abstract. Understanding how fire regimes change over time is of major importance for understanding their future impact on the Earth system, including society. Large differences in simulated burned area between fire models show that there is substantial uncertainty associated with modelling global change impacts on fire regimes. We draw here on sensitivity simulations made by seven global dynamic vegetation models participating in the Fire Model Intercomparison Project (FireMIP) to understand how differences in models translate into differences in fire regime projections. The sensitivity experiments isolate the impact of the individual drivers on simulated burned area, which are prescribed in the simulations. Specifically these drivers are atmospheric CO2 concentration, population density, land-use change, lightning and climate. The seven models capture spatial patterns in burned area. However, they show considerable differences in the burned area trends since 1921. We analyse the trajectories of differences between the sensitivity and reference simulation to improve our understanding of what drives the global trends in burned area. Where it is possible, we link the inter-model differences to model assumptions. Overall, these analyses reveal that the largest uncertainties in simulating global historical burned area are related to the representation of anthropogenic ignitions and suppression and effects of land use on vegetation and fire. In line with previous studies this highlights the need to improve our understanding and model representation of the relationship between human activities and fire to improve our abilities to model fire within Earth system model applications. Only two models show a strong response to atmospheric CO2 concentration. The effects of changes in atmospheric CO2 concentration on fire are complex and quantitative information of how fuel loads and how flammability changes due to this factor is missing. The response to lightning on global scale is low. The response of burned area to climate is spatially heterogeneous and has a strong inter-annual variation. Climate is therefore likely more important than the other factors for short-term variations and extremes in burned area. This study provides a basis to understand the uncertainties in global fire modelling. Both improvements in process understanding and observational constraints reduce uncertainties in modelling burned area trends.

scholarly journals Root growth and function of three Mojave Desert grasses in response to elevated atmospheric CO2 concentration

2000 ◽  
Vol 145 (2) ◽  
pp. 245-256 ◽  
Author(s):  
C. K. YODER ◽  
P. VIVIN ◽  
L. A. DEFALCO ◽  
J. R. SEEMANN ◽  
R. S. NOWAK
Keyword(s):  
Root Growth ◽  
Mojave Desert ◽  
Co2 Concentration ◽  
Atmospheric Co2 ◽  
Elevated Atmospheric Co2 ◽  
Atmospheric Co2 Concentration ◽  
And Function ◽  
Desert Grasses
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