Download or read book The Deep ocean Heat Uptake in Transient Climate Change written by Boyin Huang and published by . This book was released on 2002 with total page 33 pages. Available in PDF, EPUB and Kindle. Book excerpt: The deep-ocean heat uptake (DOHU) in transient climate changes is studied using an ocean general circulation model (OGCM) and its adjoint. The model configuration consists of idealized Pacific and Atlantic basins. The model is forced with the anomalies of surface heat and freshwater fluxes from a global warming scenario with a coupled model using the same ocean configuration. In the scenario CO2 concentration increases 1% per year. The heat uptake calculated from the coupled model and from the adjoint are virtually identical, showing that the heat uptake by the OGCM is a linear process. After 70 years the ocean heat uptake is almost evenly distributed within the layers above 200 m, between 200 and 700 m, and below 700 m (about 20 x 1022 J in each). The effect of anomalous surface fresh water flux on the DOHU is negligible. Analysis of CMIP-2 data for the same global warming scenario shows that qualitatively similar results apply to coupled atmosphere-ocean GCMs. The penetration of surface heat flux to the deep ocean in our OGCM occurs mainly in the North Atlantic and the Southern Ocean, since both the sensitivity of DOHU to the surface heat flux and the magnitude of anomalous surface heat flux are large in these two regions. The DOHU relies on the reduction of convection and Gent-McWilliams-Redi mixing in the North Atlantic, and the reduction of Gent-McWilliams- Redi mixing in the Southern Ocean.
Download or read book Comparing Oceanic Heat Uptake in Atmosphere ocean General Circulation Model Transient Climate Change Experiments written by Andrei P. Sokolov and published by . This book was released on 2003 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: The transient response of both surface air temperature and deep ocean temperature to an increasing external forcing strongly depends on climate sensitivity and the rate of the heat mixing into the deep ocean, estimates for both of which have large uncertainty. In this paper a method for estimating rates of oceanic heat uptake for coupled atmosphere-ocean general circulation models from results of transient climate change simulations is described. For models considered in this study, the estimates vary by a factor of 2 1/2. Nevertheless, values of oceanic heat uptake for all models fall in the range implied by the climate record for the last century. It is worth noting that the range of the model values is narrower than that consistent with observations and thus does not provide a full measure of the uncertainty in the rate of oceanic heat uptake.
Download or read book Ocean Heat Uptake in Transient Climate Change written by Boyin Huang and published by . This book was released on 2003 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: (Cont.) Experiments are carried out with values of the diffusivity of 500, 1000, and 2000 m2/sec. The total OHU is insensitive to these changes. The insensitivity is mainly due to the changes in the vertical heat flux by GMR mixing being compensated by changes in the other vertical heat flux components. In the Atlantic when the diffusivity is reduced from 1000 to 500 m2/sec, the surface warming can penetrate deeper. Therefore, the warming decreases by about 0.158C above 2000 m but increases by about 0.158C below 2500 m. Similarly, when the diffusivity is increased from 1000 to 2000 m2 s21, the surface warming becomes shallower; the warming increases by about 0.28C above 1000 m but decreases by about 0.28C below 1000 m. These changes in the vertical distribution of the OHU also contribute to the insensitivity of the total OHU to changes in the GMR mixing ...
Download or read book Climate Stabilization Targets written by National Research Council and published by National Academies Press. This book was released on 2011-02-11 with total page 298 pages. Available in PDF, EPUB and Kindle. Book excerpt: Emissions of carbon dioxide from the burning of fossil fuels have ushered in a new epoch where human activities will largely determine the evolution of Earth's climate. Because carbon dioxide in the atmosphere is long lived, it can effectively lock the Earth and future generations into a range of impacts, some of which could become very severe. Emissions reductions decisions made today matter in determining impacts experienced not just over the next few decades, but in the coming centuries and millennia. According to Climate Stabilization Targets: Emissions, Concentrations, and Impacts Over Decades to Millennia, important policy decisions can be informed by recent advances in climate science that quantify the relationships between increases in carbon dioxide and global warming, related climate changes, and resulting impacts, such as changes in streamflow, wildfires, crop productivity, extreme hot summers, and sea level rise. One way to inform these choices is to consider the projected climate changes and impacts that would occur if greenhouse gases in the atmosphere were stabilized at a particular concentration level. The book quantifies the outcomes of different stabilization targets for greenhouse gas concentrations using analyses and information drawn from the scientific literature. Although it does not recommend or justify any particular stabilization target, it does provide important scientific insights about the relationships among emissions, greenhouse gas concentrations, temperatures, and impacts. Climate Stabilization Targets emphasizes the importance of 21st century choices regarding long-term climate stabilization. It is a useful resource for scientists, educators and policy makers, among others.
Download or read book Ocean Mixing written by Michael Meredith and published by Elsevier. This book was released on 2021-09-16 with total page 386 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ocean Mixing: Drivers, Mechanisms and Impacts presents a broad panorama of one of the most rapidly-developing areas of marine science. It highlights the state-of-the-art concerning knowledge of the causes of ocean mixing, and a perspective on the implications for ocean circulation, climate, biogeochemistry and the marine ecosystem. This edited volume places a particular emphasis on elucidating the key future questions relating to ocean mixing, and emerging ideas and activities to address them, including innovative technology developments and advances in methodology. Ocean Mixing is a key reference for those entering the field, and for those seeking a comprehensive overview of how the key current issues are being addressed and what the priorities for future research are. Each chapter is written by established leaders in ocean mixing research; the volume is thus suitable for those seeking specific detailed information on sub-topics, as well as those seeking a broad synopsis of current understanding. It provides useful ammunition for those pursuing funding for specific future research campaigns, by being an authoritative source concerning key scientific goals in the short, medium and long term. Additionally, the chapters contain bespoke and informative graphics that can be used in teaching and science communication to convey the complex concepts and phenomena in easily accessible ways. - Presents a coherent overview of the state-of-the-art research concerning ocean mixing - Provides an in-depth discussion of how ocean mixing impacts all scales of the planetary system - Includes elucidation of the grand challenges in ocean mixing, and how they might be addressed
Download or read book Open Ocean Convection and the Uptake of Heat by the Deep Ocean written by Sarah Marcil and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "Understanding how the ocean takes up heat is crucial to improve prediction of the future global surface temperature increase. While many previous studies have evaluated the spatial distribution of heat content change across the global ocean, a complete explanation of the mechanisms responsible for this distribution remains largely unknown, and hence, we lack a measureable indicator of model performance that could help constrain future prediction. We examine a large ensemble of climate models to understand what creates the large inter-model variability in heat content change under global warming. Based on earlier studies on ocean vertical heat transfer, we hypothesize that open water deep convection is an important mechanism for the transfer of heat from the deep ocean to the atmosphere. Therefore, the cessation of convection, as predicted in future climate change scenario, would contribute to the increase of deep ocean heat content. We compare the convective volume and ocean heat content anomalies in 34 climate models of the IPCC Assessment Report 5. Most of models show signs of open water deep convection in the North Atlantic and in the Southern Ocean, and the variability in convective volume is linked to ocean heat content anomalies in individual models. In order to identify the most realistic climate models in term of these parameters, we compare the model convection against observations. While convection in some models is a robust predictor of deep ocean heat uptake, the models suggest a diversity of processes plays a role in the transfer of heat to the deep ocean." --
Download or read book Sensitivities of Deep ocean Heat Uptake and Heat Content to Surface Fluxes and Subgrid scale Parameters in an Ocean GCM with Idealized Geometry written by Boyin Huang and published by . This book was released on 2002 with total page 43 pages. Available in PDF, EPUB and Kindle. Book excerpt: Sensitivities of the net heat flux into the deep-ocean (Qnet) and of the deep-ocean heat content (DOC) below 700 m are studied using an ocean general circulation model and its adjoint. Both are found to have very similar sensitivities. The sensitivity to the surface freshwater flux (E-P-R) is positive in the Atlantic, but negative in the Pacific and Southern Ocean. A positive sensitivity to the downward net surface heat flux is found only in the North Atlantic north of 40ʻN and the Southern Ocean. The diapycnal diffusivity of temperature affects Qnet and DOC positively in a large area of the tropics and subtropics in both the Pacific and Atlantic Ocean. The isopycnal diffusivity contributes to Qnet and DOC mainly in the Southern Ocean. Detailed analysis indicates that the surface freshwater flux affects Qnet and DOC by changing vertical velocity, temperature stratification, and overturning circulation. The downward net surface heat flux appears to increase Qnet and DOC by strengthening vertical advection and isopycnal mixing. The contribution of isopycnal diffusivity to Qnet and DOC is largely associated with the vertical heat flux due to isopycnal mixing. Similarly, the diapycnal diffusivity of temperature modulates Qnet and DOC through the downward heat flux due to diapycnal diffusion. The uncertainties of Qnet and DOC are estimated based on the sensitivities and error bars of observed surface forcing and oceanic diffusivities. For DOC, they are about 0.7°K (1°K = 3 x 1024 J) for the isopycnal diffusivity, 0.4°K for the diapycnal diffusivity of temperature, 0.3°K for the surface freshwater flux, and 0.1°K for the net surface heat flux and zonal wind stress. Our results suggest that the heat uptake by ocean GCMs in climate experiments is sensitive to the isopycnal diffusivity as well to the diapycnal thermal diffusivity.
Download or read book A Comparison of the Behavior of Different AOGCMs in Transient Climate Change Experiments written by Andrei P. Sokolov and published by . This book was released on 2001 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: The transient response of both surface air temperature and deep ocean temperature to an increasing external forcing strongly depends on climate sensitivity and the rate of the heat mixing into the deep ocean, estimates for both of which have large uncertainty. In this paper we describe a method for estimating rates of oceanic heat uptake for coupled atmosphere/ocean general circulation models from results of transient climate change simulations. For models considered in this study, the estimates vary more than threefold. Nevertheless, values for all models fall in the 5-95% interval of the range implied by the climate record for the last century. The MIT 2D climate model, with an appropriate choice of parameters, matches changes in surface air temperature and sea level rise simulated by different models. It also reproduces the overall range of changes in precipitation.
Download or read book Constraining Climate Model Parameters from Observed 20th Century Changes written by Chris Eliot Forest and published by . This book was released on 2008 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present revised probability density functions for climate model parameters (effective climate sensitivity, the rate of deep-ocean heat uptake, and the strength of the net aerosol forcing) that are based on climate change observations from the 20th century. First, we compare observed changes in surface, upper-air, and deep-ocean temperature changes against simulations of 20th century climate in which the climate model parameters were systematically varied. The estimated 90% range of climate sensitivity is 2.0 to 5.0 K. The net aerosol forcing strength for the 1980s has 90% bounds of -0.70 to -0.27 W m-2. The rate of deep-ocean heat uptake corresponds to an effective diffusivity, Kv, with a 90% range of 0.04 to 4.1 cm2 s-1. Second, we estimate the effective climate sensitivity and rate of deep-ocean heat uptake for 11 of the IPCC AR4 AOGCMs. By comparing against the acceptable combinations inferred by the observations, we conclude that the rate of deep-ocean heat uptake for the majority of AOGCMs lie above the observationally based median value. This implies a bias in the predictions inferred from the IPCC models alone. This bias can be seen in the range of transient climate response from the AOGCMs as compared to that from the observational constraints.
Download or read book The Ocean and Cryosphere in a Changing Climate written by Intergovernmental Panel on Climate Change (IPCC) and published by Cambridge University Press. This book was released on 2022-04-30 with total page 755 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Intergovernmental Panel on Climate Change (IPCC) is the leading international body for assessing the science related to climate change. It provides policymakers with regular assessments of the scientific basis of human-induced climate change, its impacts and future risks, and options for adaptation and mitigation. This IPCC Special Report on the Ocean and Cryosphere in a Changing Climate is the most comprehensive and up-to-date assessment of the observed and projected changes to the ocean and cryosphere and their associated impacts and risks, with a focus on resilience, risk management response options, and adaptation measures, considering both their potential and limitations. It brings together knowledge on physical and biogeochemical changes, the interplay with ecosystem changes, and the implications for human communities. It serves policymakers, decision makers, stakeholders, and all interested parties with unbiased, up-to-date, policy-relevant information. This title is also available as Open Access on Cambridge Core.
Download or read book Investigating the Impact of Direct Effects of Radiative Forcing on Ocean Heat Uptake written by Molly Syme and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "The ocean's response to direct atmospheric effects of increased carbon dioxide's (CO2) radiative forcing is examined. These direct effects are defined as physical climate changes that respond to forcing on a fast timescale of a few years, independent of the slower surface warming that the forcing also provokes. To evaluate how these directeffects impact ocean heat uptake (OHU), output of atmospheric climate simulations are used to force an ocean-only model with comprehensive boundary conditions. Perturbation simulations with the prescribed response to a quadrupling of atmospheric CO2 include altered surface winds, freshwater fluxes, and downwelling shortwave radiation boundary conditions. The perturbation simulations show that the intensification and poleward shift of surface winds, particularly in the Southern Ocean, strengthen the overturning circulation both in the Pacific and Atlantic Oceans. This, in turn, has a cooling effect on the global ocean at shallow depths. A two-layer energy balance model designed to capture transient, global-mean climate change, is adapted to accommodate the altered ocean heat uptake from direct effects. To assess the relative significance of direct effects on OHU, additional simulations are conducted by perturbing the ocean-only model with temperature-dependent changes in atmospheric fields. The total atmospheric response to radiative forcing is decomposed between the direct response and the temperature-dependent response using results from coupled atmosphere-ocean climate simulations. Perturbations to the atmospheric forcing parameters evolve as the ocean model's global-mean sea surface temperature increases which mimics the time-dependence of the response to increased CO2 in coupled models. Together, the results build understanding of how ocean heat uptake is impacted by the atmospheric response to CO2 radiative forcing." --
Download or read book Assessment of Approaches to Updating the Social Cost of Carbon written by National Academies of Sciences, Engineering, and Medicine and published by National Academies Press. This book was released on 2016-03-26 with total page 73 pages. Available in PDF, EPUB and Kindle. Book excerpt: The social cost of carbon (SCC) for a given year is an estimate, in dollars, of the present discounted value of the damage caused by a 1-metric ton increase in CO2 emissions into the atmosphere in that year; or equivalently, the benefits of reducing CO2 emissions by the same amount in that given year. The SCC is intended to provide a comprehensive measure of the monetized value of the net damages from global climate change from an additional unit of CO2, including, but not limited to, changes in net agricultural productivity, energy use, human health effects, and property damages from increased flood risk. Federal agencies use the SCC to value the CO2 emissions impacts of various policies including emission and fuel economy standards for vehicles, regulations of industrial air pollutants from industrial manufacturing, emission standards for power plants and solid waste incineration, and appliance energy efficiency standards. There are significant challenges to estimating a dollar value that reflects all the physical, human, ecological, and economic impacts of climate change. Recognizing that the models and scientific data underlying the SCC estimates evolve and improve over time, the federal government made a commitment to provide regular updates to the estimates. To assist with future revisions of the SCC, the Interagency Working Group on the Social Cost of Carbon (IWG) requested the National Academies of Sciences, Engineering, and Medicine complete a study that assessed the merits and challenges of a limited near-term update to the SCC and of a comprehensive update of the SCC to ensure that the estimates reflect the best available science. This interim report focuses on near-term updates to the SCC estimates.
Download or read book The Role of High latitude Oceans in Transient Climate Change written by Yavor Krasimirov Kostov and published by . This book was released on 2016 with total page 119 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis we explore the role of the large-scale ocean circulation in the North Atlantic and the Southern Ocean (SO) in setting the regional and globally averaged sea surface temperature (SST) response to atmospheric forcing. We focus on the impact of anthropogenic greenhouse gases (AGHGs) and the Antarctic ozone hole and use output from general circulation models (GCMs) to estimate the corresponding climate response functions (CRFs). We show that the strength and the vertical extent of the time-mean Atlantic Meridional Overturning Circulation (AMOC) set the effective heat capacity of the World Ocean and affect the global CRF to greenhouse gas (GHG) forcing. A large fraction of the anomalous surface heat uptake induced by GHGs takes place over the North Atlantic. However, the SO also plays a significant role in removing excess heat from the atmosphere. Compared to the rest of the World Ocean, the SO warms at a much slower rate under GHG forcing. In this region the background Meridional Overturning Circulation (MOC) upwells unmodified deep water masses to the surface where they take up atmospheric heat. The modified water masses are then advected northward and subducted in the mid-latitudes. This geographical imprint of the MOC is reflected in the regional CRFs to GHGs, as seen in idealized numerical experiments with GCMs. However, GHGs are not the only major source of anthropogenic forcing on the SO. Stratospheric ozone depletion around Antarctica gives rise to an atmospheric pattern similar to the positive phase of the Southern Annular Mode (SAM): a strengthening and a southward shift of the westerlies. This poleward intensification of the winds changes the ocean circulation and gives rise to an SST response. We examine the SO CRF to a SAM pattern that arises either in the form of natural variability in unforced control experiments or as a result of imposed ozone perturbations. We analyze the SO SST response to SAM on multiple timescales and across an ensemble of GCMs from the Climate Modeling Intercomparison Project phase 5 (CMIP5). We show that the corresponding SO CRF is governed by the anomalous wind-driven MOC redistributing the background heat reservoir. The intermodel diversity in the fast and slow SST responses to SAM is partly explained by differences in the climatological thermal stratification across the ensemble of GCMs. Furthermore, we demonstrate that the sea ice response to SAM in models is very well correlated with the geographic pattern of the SST anomalies. Finally, we convolve our estimated CRFs with timeseries of historical forcing to recover the SO SST trends in numerical simulations and in observations. We contrast the multidecadal SO cooling trends against the SST warming rate in the Northern Hemisphere high latitudes. Our results imply that the recent cooling in the SO may be explained by the Antarctic ozone hole projecting on a positive SAM trend. We furthermore attempt to understand why CMIP5 models have been unable to reproduce the observed negative SST trends in the SO and instead predict regional warming. Many GCM simulations underestimate the historical SAM evolution. Another subset of CMIP5 models have biases in their climatological SO stratification, which affects their SO CRFs to SAM. The successful application of the CRF framework in the context of observed and simulated SST trends validates the results of our analysis. We are thus able to interpret the CRFs as inherent characteristics of the climate system and elucidate the importance of the high latitude oceans in transient climate change.
Download or read book The Ocean s Role in the Transient Response of Climate to Abrupt Greenhouse Gas Forcing written by and published by . This book was released on 2014 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: We study the role of the ocean in setting the patterns and timescale of the transient response of the climate to anthropogenic greenhouse gas forcing. A novel framework is set out which involves integration of an ocean-only model in which the anthropogenic temperature signal is forced from the surface by anomalous downwelling heat fluxes and damped at a rate controlled by a 'climate feedback' parameter. We observe a broad correspondence between the evolution of the anthropogenic temperature (Tanthro) in our simplified ocean-only model and that of coupled climate models perturbed by a quadrupling of CO2. This suggests that many of the mechanisms at work in fully coupled models are captured by our idealized ocean-only system. The framework allows us to probe the role of the ocean in delaying warming signals in the Southern Ocean and in the northern North Atlantic, and in amplifying the warming signal in the Arctic. By comparing active and passive temperature-like tracers we assess the degree to which changes in ocean circulation play a role in setting the distribution and evolution of Tanthro. The background ocean circulation strongly influences the large-scale patterns of ocean heat uptake and storage, such that Tanthro is governed by an advection/diffusion equation and weakly damped to the atmosphere at a rate set by climate feedbacks. Where warming is sufficiently small, for example in the Southern Ocean, changes in ocean circulation play a secondary role. In other regions, most noticeably in the North Atlantic, changes in ocean circulation induced by Tanthro are central in shaping the response.
Download or read book The Ocean s Role in Climate Change written by Alexander Polonsky and published by Cambridge Scholars Publishing. This book was released on 2019-05-21 with total page 294 pages. Available in PDF, EPUB and Kindle. Book excerpt: The principal focus of this book is the physical processes in the World Ocean which regulate the interannual-to-multidecadal natural variability of the climate system, and some key atmospheric and marine manifestations of this variability. It analyses a number of Atlantic and Indo-Pacific signals, and describes their regional atmospheric and marine manifestations. The role of the Ocean in the recent hiatus of global warming and the probability of abrupt climate change due to thermohaline catastrophe are also assessed. The book pays special attention to the change of parameters of synoptic atmospheric disturbances over the Northern Hemisphere and its sub-regions in different phases of the natural quasi-periodical climatic signals. It will appeal to oceanographers, climatologists, meteorologists, hydrologist, geographers and the general reader interested in the problem of climate change all over the globe, especially with regards to Eastern Europe and the Black Sea region.
Download or read book Abrupt Climate Change written by National Research Council and published by National Academies Press. This book was released on 2002-04-23 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt: The climate record for the past 100,000 years clearly indicates that the climate system has undergone periodic-and often extreme-shifts, sometimes in as little as a decade or less. The causes of abrupt climate changes have not been clearly established, but the triggering of events is likely to be the result of multiple natural processes. Abrupt climate changes of the magnitude seen in the past would have far-reaching implications for human society and ecosystems, including major impacts on energy consumption and water supply demands. Could such a change happen again? Are human activities exacerbating the likelihood of abrupt climate change? What are the potential societal consequences of such a change? Abrupt Climate Change: Inevitable Surprises looks at the current scientific evidence and theoretical understanding to describe what is currently known about abrupt climate change, including patterns and magnitudes, mechanisms, and probability of occurrence. It identifies critical knowledge gaps concerning the potential for future abrupt changes, including those aspects of change most important to society and economies, and outlines a research strategy to close those gaps. Based on the best and most current research available, this book surveys the history of climate change and makes a series of specific recommendations for the future.
Download or read book Thriving on Our Changing Planet written by National Academies of Sciences, Engineering, and Medicine and published by National Academies Press. This book was released on 2019-01-20 with total page 717 pages. Available in PDF, EPUB and Kindle. Book excerpt: We live on a dynamic Earth shaped by both natural processes and the impacts of humans on their environment. It is in our collective interest to observe and understand our planet, and to predict future behavior to the extent possible, in order to effectively manage resources, successfully respond to threats from natural and human-induced environmental change, and capitalize on the opportunities â€" social, economic, security, and more â€" that such knowledge can bring. By continuously monitoring and exploring Earth, developing a deep understanding of its evolving behavior, and characterizing the processes that shape and reshape the environment in which we live, we not only advance knowledge and basic discovery about our planet, but we further develop the foundation upon which benefits to society are built. Thriving on Our Changing Planet presents prioritized science, applications, and observations, along with related strategic and programmatic guidance, to support the U.S. civil space Earth observation program over the coming decade.
