38 results on '"Toniazzo T"'
Search Results
2. Challenges and prospects for reducing coupled climate model sst biases in the eastern tropical atlantic and pacific oceans: The U.S. Clivar eastern tropical oceans synthesis working group
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Zuidema, P, Chang, P, Medeiros, B, Kirtman, BP, Mechoso, R, Schneider, EK, Toniazzo, T, Richter, I, Small, RJ, Bellomo, K, Brandt, P, De Szoeke, S, Farrar, JT, Jung, E, Kato, S, Li, M, Patricola, C, Wang, Z, Wood, R, and Xu, Z
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Meteorology & Atmospheric Sciences ,Astronomical and Space Sciences ,Atmospheric Sciences ,Physical Geography and Environmental Geoscience - Abstract
Targeted observations to improve numerical forecasts of high-impact weather events over the past two decades, particularly during the THORPEX era (2005-14), are evaluated.
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- 2016
3. Diffusive grain-surface chemistry involving the atoms and diatomic molecules of two elements
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Rae, J. G. L., Green, N. J. B., Hartquist, T. W., Pilling, M. J., and Toniazzo, T.
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Astrophysics - Abstract
A model of the grain surface chemistry involving the accretion of atoms of two different elements, X and Y, and their reactions to form species X_2, XY, and Y_2 was examined for a wide range of choices for the values of its three free parameters - the accretion rate of X and Y, the desorption rate of X and the grain surface sweeping time of Y, all considered relative to the grain surface sweeping rate of X. Relative production rates of the diatomics were calculated with five methods involving, respectively, a high-order truncation of the master equation, a low-order truncation of the master equation, the standard deterministic rate equation approach, a modified rate equation approach and a set of approximations which are in some cases appropriate for accretion dominated chemistry. The accuracies of the relative production rates calculated with the different methods were assessed for the wide range of model parameters. The more accurate of the low-truncation master equation calculations and the standard deterministic rate equation approach gives results which are in most cases within ten or twenty per cent of the results given by the high-truncation master equation calculations. For many cases, the more accurate of the low order truncation and the standard deterministic rate equation approaches is indicated by a consideration of the average number of atoms of the two species on the grain's surface., Comment: 10 pages, 7 figures. Accepted for publication in Astronomy & Astrophysics. Additional figures can be found at http://ast.leeds.ac.uk/~jglr
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- 2003
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4. Reconciling and Improving Formulations for Thermodynamics and Conservation Principles in Earth System Models (ESMs)
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Lauritzen, P. H., primary, Kevlahan, N. K.‐R., additional, Toniazzo, T., additional, Eldred, C., additional, Dubos, T., additional, Gassmann, A., additional, Larson, V. E., additional, Jablonowski, C., additional, Guba, O., additional, Shipway, B., additional, Harrop, B. E., additional, Lemarié, F., additional, Tailleux, R., additional, Herrington, A. R., additional, Large, W., additional, Rasch, P. J., additional, Donahue, A. S., additional, Wan, H., additional, Conley, A., additional, and Bacmeister, J. T., additional
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- 2022
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5. Climatic Impact of a Greenland Deglaciation and Its Possible Irreversibility
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Toniazzo, T., Gregory, J. M., and Huybrechts, P.
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- 2004
6. Can reducing the incoming energy flux over the Southern Ocean in a CGCM improve its simulation of tropical climate?
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Mechoso, Carlos R., Losada, Teresa, Koseki, S., Mohino, Elsa, Keenlyside, N., Castaño-Tierno, Antonio, Myers, T. A., Rodríguez-Fonseca, Belén, and Toniazzo, T.
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GCMs ,Low clouds ,ITCZ - Abstract
Atmosphere-ocean general circulation models (CGCMs) show important systematic errors. Simulated precipitation in the tropics is generally overestimated over the oceans south of the equator, and stratocumulus (SCu) clouds are underestimated above too warm sea surface temperatures (SSTs). In the extratropics, SSTs are also too warm over the Southern Ocean. We argue that ameliorating these extratropical errors in a CGCM can result in an improved model's performance in the tropics depending upon the success in simulating the sensitivity of SCu to underlying SST. Our arguments are supported by the very different response obtained with two CGCMs to an idealized reduction of solar radiation flux incident at the top of the atmosphere over the Southern Ocean. It is shown that local perturbation impacts are very similar in the two models but that SST reductions in the SCu regions of the southern subtropics are stronger in the model with the stronger SCu-SST feedbacks., NOAA's Climate Program Office, Climate Variability and Predictability Program Award. Grant Number: NA14OAR4310278. European Union Seventh Framework Programme. Grant Numbers: FP7/2007–2013, 60352
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- 2016
7. Structural decomposition of decadal climate prediction errors: A Bayesian approach
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Zanchettin, D, Gaetan, C, Arisido, M, Modali, K, Toniazzo, T, Keenlyside, N, Rubino, A, Arisido, MW, Zanchettin, D, Gaetan, C, Arisido, M, Modali, K, Toniazzo, T, Keenlyside, N, Rubino, A, and Arisido, MW
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Decadal climate predictions use initialized coupled model simulations that are typically affected by a drift toward a biased climatology determined by systematic model errors. Model drifts thus reflect a fundamental source of uncertainty in decadal climate predictions. However, their analysis has so far relied on ad-hoc assessments of empirical and subjective character. Here, we define the climate model drift as a dynamical process rather than a descriptive diagnostic. A unified statistical Bayesian framework is proposed where a state-space model is used to decompose systematic decadal climate prediction errors into an initial drift, seasonally varying climatological biases and additional effects of co-varying climate processes. An application to tropical and south Atlantic sea-surface temperatures illustrates how the method allows to evaluate and elucidate dynamic interdependencies between drift, biases, hindcast residuals and background climate. Our approach thus offers a methodology for objective, quantitative and explanatory error estimation in climate predictions
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- 2017
8. Gravity-wave-induced perturbations in marine stratocumulus
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Allen, G., Vaughan, G., Toniazzo, T., Coe, H., Connolly, P., Yuter, S. E., Burleyson, C. D., Minnis, P., and Ayers, J. K.
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breaking ,drizzle ,Atmospheric Science ,pockets of open cells ,variability ,gravity waves ,cloud microphysics ,mesoscale ,dynamics ,precipitation ,stratocumulus ,numerical simulations ,east pacific ,southeast pacific stratocumulus ,vocals-rex ,vocals ,scale interactions ,Physics::Atmospheric and Oceanic Physics - Abstract
We discuss the role of atmospheric gravity waves in modulating cloud radiative and dynamical properties over the southeast Pacific. Satellite imagery and satellite-retrieved cloud properties during October 2008 illustrate three distinct episodes of horizontal propagation of gravity wave trains across the large-scale stratocumulus (Sc) cloud deck capping the local marine boundary layer. In one period, 79 October 2008, the waves modulated cloud-top-height by up to 400 m peak-to-trough, propagating perpendicular to the synoptic boundary layer flow with phase speed 15.3 m s1, period approximate to 1 h and horizontal wavelength 55 km. The gravity waves were observed to be non-dispersive. These waves were first evident in the cloud deck near 30 degrees S, 85 degrees W during a 24 h period beginning at midday on 7 October 2008, and propagated northeastward toward the Peruvian coast for the following 48 h. During this time they induced both reversible and non-reversible changes in cloud-radiative and cloud-dynamic properties, such that areas of clear sky developed in the troughs of passing wave-fronts. These pockets of open cells persisted long after the passage of the gravity waves, advecting northwestward with the background wind. Using the analysis fields of the European Centre for Medium-Range Weather Forecasts in conjunction with infrared and microwave satellite imagery, we show that these gravity waves emerged from a disturbed subtropical jet stream. The radiant of the waves was coincident in all cases with centres of large negative residuals in nonlinear balance, suggesting that geostrophic readjustment of sharply divergent flows associated with the disturbed jet provided a source for the wave energy. Conversely, gravity waves were not observed in more quiescent jet conditions. This case study highlights the important and irreversible effects that gravity waves propagating in the troposphere can have on cloud radiative properties (and hence surface radiation budgets) over a very wide area. It also highlights the importance of synoptic influence on Sc-covered marine boundary layers. Copyright (c) 2012 Royal Meteorological Society
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- 2013
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9. The VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx) : goals, platforms, and field operations
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Wood, R., Mechoso, C. R., Bretherton, C. S., Weller, R. A., Huebert, B., Straneo, F., Albrecht, B. A., Coe, H., Allen, G., Vaughan, G., Daum, P., Fairall, C., Chand, D., Gallardo Klenner, L., Garreaud, R., Grados, C., Covert, D. S., Bates, T. S., Krejci, Radovan, Russell, L. M., de Szoeke, S., Brewer, A., Yuter, S. E., Springston, S. R., Chaigneau, A., Toniazzo, T., Minnis, P., Palikonda, R., Abel, S. J., Brown, W. O. J., Williams, S., Fochesatto, J., Brioude, J., Bower, K. N., Wood, R., Mechoso, C. R., Bretherton, C. S., Weller, R. A., Huebert, B., Straneo, F., Albrecht, B. A., Coe, H., Allen, G., Vaughan, G., Daum, P., Fairall, C., Chand, D., Gallardo Klenner, L., Garreaud, R., Grados, C., Covert, D. S., Bates, T. S., Krejci, Radovan, Russell, L. M., de Szoeke, S., Brewer, A., Yuter, S. E., Springston, S. R., Chaigneau, A., Toniazzo, T., Minnis, P., Palikonda, R., Abel, S. J., Brown, W. O. J., Williams, S., Fochesatto, J., Brioude, J., and Bower, K. N.
- Abstract
The VAMOS(1) Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx) was an international field program designed to make observations of poorly understood but critical components of the coupled climate system of the southeast Pacific. This region is characterized by strong coastal upwelling, the coolest SSTs in the tropical belt, and is home to the largest subtropical stratocumulus deck on Earth. The field intensive phase of VOCALS-REx took place during October and November 2008 and constitutes a critical part of a broader CLIVAR program (VOCALS) designed to develop and promote scientific activities leading to improved understanding, model simulations, and predictions of the southeastern Pacific (SEP) coupled ocean-atmosphere-land system, on diurnal to interannual timescales. The other major components of VOCALS are a modeling program with a model hierarchy ranging from the local to global scales, and a suite of extended observations from regular research cruises, instrumented moorings, and satellites. The two central themes of VOCALS-REx focus upon (a) links between aerosols, clouds and precipitation and their impacts on marine stratocumulus radiative properties, and (b) physical and chemical couplings between the upper ocean and the lower atmosphere, including the role that mesoscale ocean eddies play. A set of hypotheses designed to be tested with the combined field, monitoring and modeling work in VOCALS is presented here. A further goal of VOCALS-REx is to provide datasets for the evaluation and improvement of large-scale numerical models. VOCALS-REx involved five research aircraft, two ships and two surface sites in northern Chile. We describe the instrument pay-loads and key mission strategies for these platforms and give a summary of the missions conducted., authorCount :34
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- 2011
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10. South East Pacific atmospheric composition and variability sampled = ong 20 degrees S during VOCALS-REx
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Allen, G., Coe, H., Clarke, A., Bretherton, C., Wood, R., Abel, S. J., Barrett, P., Brown, P., George, R., Freitag, S., McNaughton, C., Howell, S., Shank, L., Kapustin, V., Brekhovskikh, V., Kleinman, L., Lee, Y-N, Springston, S., Toniazzo, T., Krejci, Radovan, Fochesatto, J., Shaw, G., Krecl, P., Brooks, B., McMeeking, G., Bower, K. N., Williams, P. I., Crosier, J., Crawford, I., Connolly, P., Allan, J. D., Covert, D., Bandy, A. R., Russell, L. M., Trembath, J., Bart, M., McQuaid, J. B., Wang, J., Chand, D., Allen, G., Coe, H., Clarke, A., Bretherton, C., Wood, R., Abel, S. J., Barrett, P., Brown, P., George, R., Freitag, S., McNaughton, C., Howell, S., Shank, L., Kapustin, V., Brekhovskikh, V., Kleinman, L., Lee, Y-N, Springston, S., Toniazzo, T., Krejci, Radovan, Fochesatto, J., Shaw, G., Krecl, P., Brooks, B., McMeeking, G., Bower, K. N., Williams, P. I., Crosier, J., Crawford, I., Connolly, P., Allan, J. D., Covert, D., Bandy, A. R., Russell, L. M., Trembath, J., Bart, M., McQuaid, J. B., Wang, J., and Chand, D.
- Abstract
The VAMOS Ocean-Cloud-Atmosphere-Land Regional Experiment (VOCALS-REx) was conducted from 15 October to 15 November 2008 in the South East Pacific (SEP) region to investigate interactions between land, sea and atmosphere in this unique tropical eastern ocean environment and to improve the skill of global and regional models in = presenting the region. This study synthesises selected aircraft, ship = d surface site observations from VOCALS-REx to statistically summarise = d characterise the atmospheric composition and variability of the = rine Boundary Layer (MBL) and Free Troposphere (FT) along the 20 = grees S parallel between 70 degrees W and 85 degrees W. Significant = nal gradients in mean MBL sub-micron aerosol particle size and = mposition, carbon monoxide, sulphur dioxide and ozone were seen over = e campaign, with a generally more variable and polluted coastal = vironment and a less variable, more pristine remote maritime regime. = adients in aerosol and trace gas concentrations were observed to be = sociated with strong gradients in cloud droplet number. The FT was = ten more polluted in terms of trace gases than the MBL in the mean; = wever increased variability in the FT composition suggests an episodic = ture to elevated concentrations. This is consistent with a complex = rtical interleaving of airmasses with diverse sources and hence = llutant concentrations as seen by generalised back trajectory = alysis, which suggests contributions from both local and long-range = urces. Furthermore, back trajectory analysis demonstrates that the = served zonal gradients both in the boundary layer and the free = oposphere are characteristic of marked changes in airmass history with = stance offshore - coastal boundary layer airmasses having been in = cent contact with the local land surface and remote maritime airmasses = ving resided over ocean for in excess of ten days. Boundary layer = mposition to the east of 75 degrees W was observed to be dominated by = astal e, authorCount :39
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- 2011
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11. Gravity-wave-induced perturbations in marine stratocumulus
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Allen, G., primary, Vaughan, G., additional, Toniazzo, T., additional, Coe, H., additional, Connolly, P., additional, Yuter, S. E., additional, Burleyson, C. D., additional, Minnis, P., additional, and Ayers, J. K., additional
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- 2012
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12. On the (ir-)reversibility of Greenland ice sheet melting in a warming climate
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Huybrechts, Philippe, Ridley, J., Toniazzo, T., Gregory, J., Huybrechts, Philippe, Ridley, J., Toniazzo, T., and Gregory, J.
- Abstract
It is often suggested that the Greenland ice sheet is a relict ice mass left over from the Ice Ages. In that case the ice sheet would not regrow to its present configuration under present-day climatic conditions if it were to melt away in a warmer climate, except for some residual mountain glaciers in the east. The most cited reasons for this alleged hysteresis are the height-mass balance feedback and the albedo-temperature feedback. Future climatic warming is expected to cause more melting on the Greenland ice sheet, resulting in an overall shrinking of the ice sheet. For a warming in excess of some 3°C, models predict that the surface mass balance will become negative such that the ice sheet can no longer be sustained and starts to gradually disintegrate. An intriguing question is whether there exist points-of-no-return once such a disintegration has set in beyond which complete removal of the ice sheet were to become irreversible, even if climatic conditions were to revert to present-day conditions. To investigate these issues, we have inserted a 3-D thermomechanical model of the Greenland ice sheet in the HadCM3 atmosphere-ocean general circulation model. Under constant 4xCO2 conditions, the Greenland ice sheet is found to disintegrate to less than 5% of its current volume within 3000 years. At different moments in time, we interrupt the melting process by inserting a 1xCO2 climate and let the ice sheet evolve to a new steady state. We also investigate the end member in which the ice sheet is entirely removed and bedrock topography has been uplifted. The original contribution of our approach is that precipitation and temperature patterns are allowed to fully interact with the changing topography and surface type of the Greenland continent.
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- 2004
13. South East Pacific atmospheric composition and variability sampled along 20° S during VOCALS-REx
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Allen, G., primary, Coe, H., additional, Clarke, A., additional, Bretherton, C., additional, Wood, R., additional, Abel, S. J., additional, Barrett, P., additional, Brown, P., additional, George, R., additional, Freitag, S., additional, McNaughton, C., additional, Howell, S., additional, Shank, L., additional, Kapustin, V., additional, Brekhovskikh, V., additional, Kleinman, L., additional, Lee, Y.-N., additional, Springston, S., additional, Toniazzo, T., additional, Krejci, R., additional, Fochesatto, J., additional, Shaw, G., additional, Krecl, P., additional, Brooks, B., additional, McMeeking, G., additional, Bower, K. N., additional, Williams, P. I., additional, Crosier, J., additional, Crawford, I., additional, Connolly, P., additional, Allan, J. D., additional, Covert, D., additional, Bandy, A. R., additional, Russell, L. M., additional, Trembath, J., additional, Bart, M., additional, McQuaid, J. B., additional, Wang, J., additional, and Chand, D., additional
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- 2011
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14. Large-scale and synoptic meteorology in the south-east Pacific during the observations campaign VOCALS-REx in austral Spring 2008
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Toniazzo, T., primary, Abel, S. J., additional, Wood, R., additional, Mechoso, C. R., additional, Allen, G., additional, and Shaffrey, L. C., additional
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- 2011
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15. The VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx): goals, platforms, and field operations
- Author
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Wood, R., primary, Mechoso, C. R., additional, Bretherton, C. S., additional, Weller, R. A., additional, Huebert, B., additional, Straneo, F., additional, Albrecht, B. A., additional, Coe, H., additional, Allen, G., additional, Vaughan, G., additional, Daum, P., additional, Fairall, C., additional, Chand, D., additional, Gallardo Klenner, L., additional, Garreaud, R., additional, Grados, C., additional, Covert, D. S., additional, Bates, T. S., additional, Krejci, R., additional, Russell, L. M., additional, de Szoeke, S., additional, Brewer, A., additional, Yuter, S. E., additional, Springston, S. R., additional, Chaigneau, A., additional, Toniazzo, T., additional, Minnis, P., additional, Palikonda, R., additional, Abel, S. J., additional, Brown, W. O. J., additional, Williams, S., additional, Fochesatto, J., additional, Brioude, J., additional, and Bower, K. N., additional
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- 2011
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16. Southeast Pacific atmospheric composition and variability sampled along 20° S during VOCALS-REx
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Allen, G., primary, Coe, H., additional, Clarke, A., additional, Bretherton, C., additional, Wood, R., additional, Abel, S. J., additional, Barrett, P., additional, Brown, P., additional, George, R., additional, Freitag, S., additional, McNaughton, C., additional, Howell, S., additional, Shank, L., additional, Kapustin, V., additional, Brekhovskikh, V., additional, Kleinman, L., additional, Lee, Y.-N., additional, Springston, S., additional, Toniazzo, T., additional, Krejci, R., additional, Fochesatto, J., additional, Shaw, G., additional, Krecl, P., additional, Brooks, B., additional, McKeeking, G., additional, Bower, K. N., additional, Williams, P. I., additional, Crosier, J., additional, Crawford, I., additional, Connolly, P., additional, Covert, D., additional, and Bandy, A. R., additional
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- 2011
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17. Large-scale and synoptic meteorology in the South-East Pacific during the observations campaign VOCALS-REx in Spring 2008
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Toniazzo, T., primary, Abel, S. J., additional, Wood, R., additional, Mechoso, C. R., additional, Allen, G., additional, and Shaffrey, L. C., additional
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- 2011
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18. Climatic impact of a Greenland deglaciation and its possible irreversibility
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Toniazzo, T., Gregory, J. M., Huybrechts, Philippe, Toniazzo, T., Gregory, J. M., and Huybrechts, Philippe
- Abstract
Warmer climate conditions persisting for a period of many centuries could lead tothe disappearance of the Greenland ice-sheet, with a related 7 m rise in sea-level. We address the question of whether the ice-sheet could be regenerated if pre-industrial climate conditions were re-established after its melting. We use the HadCM3 coupled atmosphere-ocean GCM to simulate the global and regional climate with preindustrial atmospheric greenhouse-gas composition and the Greenland ice-sheet removed. Two separate cases are considered. In one, the surface topography of Greenland is given by that of the bedrock currently buried under the ice-sheet. In the other, a readjustmentto isostatic equilibrium of the unloaded orography is taken into account, giving higher elevations. In both cases, there is greater summer melting than in the current climate, leading to partially snow-free summers with much higher temperatures. On the long-term average, there is no accumulation of snow. The implication of this result is that the removal of the Greenland ice-sheet due to a prolonged climatic warming would not be reversible.
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- 2003
19. The VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx): goals, platforms, and field operations
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Wood, R., primary, Bretherton, C. S., additional, Mechoso, C. R., additional, Weller, R. A., additional, Huebert, B., additional, Straneo, F., additional, Albrecht, B. A., additional, Coe, H., additional, Allen, G., additional, Vaughan, G., additional, Daum, P., additional, Fairall, C., additional, Chand, D., additional, Gallardo Klenner, L., additional, Garreaud, R., additional, Grados Quispe, C., additional, Covert, D. S., additional, Bates, T. S., additional, Krejci, R., additional, Russell, L. M., additional, de Szoeke, S., additional, Brewer, A., additional, Yuter, S. E., additional, Springston, S. R., additional, Chaigneau, A., additional, Toniazzo, T., additional, Minnis, P., additional, Palikonda, R., additional, Abel, S. J., additional, Brown, W. O. J., additional, Williams, S., additional, Fochesatto, J., additional, and Brioude, J., additional
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- 2010
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20. Climate and snow accumulation on ice-free Greenland
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Toniazzo, T., Gregory, J. M., Huybrechts, Philippe, Toniazzo, T., Gregory, J. M., and Huybrechts, Philippe
- Abstract