Comparing water, energy and entropy budgets of aquaplanet climate attractors

2020 ◽  
Author(s):  
Charline Ragon ◽  
Valerio Lembo ◽  
Valerio Lucarini ◽  
Jérôme Kasparian ◽  
Maura Brunetti
Keyword(s):  
Steady State ◽  
Sea Ice ◽  
Diagnostic Tool ◽  
Climate Models ◽  
Water Mass ◽  
Statistical Properties ◽  
Climate System ◽  
Irreversible Processes ◽  
Energy Budgets ◽  
Energy Cycle

<p>The climate system can be seen as a thermal engine that generates entropy by irreversible processes and achieves a steady state by redistributing the input solar energy among its different components (ocean, atmosphere, etc) and by balancing the energy, water mass and entropy budgets over all the spatial scales. Biases in modern climate models are generally related to the fact that their statistical properties are not well represented, giving rise to imperfect closures of the energy cycle. Thus, a proper measurement of the efficiency of the thermal engine in each climate model is needed. Moreover, possible steady states (attractors) that can be approached at climate tipping-points are characterised by different feedbacks becoming dominant in the thermal engine.</p><p>We apply the Thermodynamic Diagnostic Tool (<em>TheDiaTo</em>) [1] to the attractors recently obtained using the MIT general circulation model (<em>MITgcm</em>) in a coupled aquaplanet [2], a planet where the ocean covers the entire globe. Such coupled aquaplanets, where nonlinear interactions between atmosphere, ocean and sea ice are fully taken into account, provide a relevant framework to understand the role of the main feedbacks at play in the climate system. Five attractors have been found, ranging from snowball (where ice covers the entire planet) to hot state conditions (where ice completely disappears) [2].</p><p>Using <em>TheDiaTo</em>, we analyse the five climate attractors by estimating: <span> a) the energy budgets and meridional energy transports; b) the water mass and latent energy budgets and respective meridional transports; c) the Lorenz Energy Cycle; d) the material entropy production. </span><span>We consider different coupled atmosphere-ocean-sea ice configurations and cloud parameterizations of <em>MITgcm</em> where the energy balance at the top of the atmosphere is progressively better closed in order to understand the occurrence of possible biases in the statistical properties of each attractor. </span></p><p>Our contribution will help clarify the thermodynamic differences in climate attractors and their stability to external perturbations that could shift the climate from a steady state to the other.</p><p><span>[1] Lembo V., Lunkeit F., Lucarini V., TheDiaTo (v1.0) – a new diagnostic tool for water, energy amd entropy budgets in climate models, Geosci. Model Dev. 12, 3805-3834 (2019)</span></p><p><span>[2] Brunetti M., Kasparian J., Vérard C., Co-existing climate attractors in a coupled aquaplanet, Climate Dynamics 53, 6293-6308 (2019) </span></p>

scholarly journals TheDiaTo (v1.0) – A new diagnostic tool for water, energy and entropy budgets in climate models

2019 ◽  
Author(s):  
Valerio Lembo ◽  
Frank Lunkeit ◽  
Valerio Lucarini
Keyword(s):  
Entropy Production ◽  
Energy Budget ◽  
Diagnostic Tool ◽  
Hydrological Cycle ◽  
Heat Fluxes ◽  
Climate System ◽  
Irreversible Processes ◽  
Energy Budgets ◽  
Energy Cycle ◽  
Lorenz Energy Cycle

Abstract. This work presents Thermodynamic Diagnostic Tool (TheDiaTo), a novel diagnostic tool for studying the thermodynamics of the climate systems with a wide range of applications, from sensitivity studies to model tuning. It includes a number of modules for assessing the internal energy budget, the hydrological cycle, the Lorenz Energy Cycle and the material entropy production, respectively. The routine receives as inputs energy fluxes at surface and at the Top-of-Atmosphere (TOA), for the computation of energy budgets at Top-of-Atmosphere (TOA), at the surface, and in the atmosphere as a residual. Meridional enthalpy transports are also computed from the divergence of the zonal mean energy budget fluxes; location and intensity of peaks in the two hemispheres are then provided as outputs. Rainfall, snowfall and latent heat fluxes are received as inputs for computing the water mass and latent energy budgets. If a land-sea mask is provided, the required quantities are separately computed over continents and oceans. The diagnostic tool also computes the Lorenz Energy Cycle (LEC) and its storage/conversion terms as annual mean global and hemispheric values. In order to achieve this, one needs to provide as input three-dimensional daily fields of horizontal wind velocity and temperature in the troposphere. Two methods have been implemented for the computation of the material entropy production, one relying on the convergence of radiative heat fluxes in the atmosphere (indirect method), one combining the irreversible processes occurring in the climate system, particularly heat fluxes in the boundary layer, the hydrological cycle and the kinetic energy dissipation as retrieved from the residuals of the LEC. A version of these diagnostics has been developed as part of the Earth System Model eValuation Tool (ESMValTool) v2.0a1, in order to assess the performances of CMIP6 model simulations, and will be available in the next release of the tool. The aim of this software is to provide a comprehensive picture of the thermodynamics of the climate system as reproduced in the state-of-the-art coupled general circulation models. This can prove useful for better understanding anthropogenic and natural climate change, paleoclimatic climate variability, and climatic tipping points.

scholarly journals TheDiaTo (v1.0) – a new diagnostic tool for water, energy and entropy budgets in climate models

2019 ◽  
Vol 12 (8) ◽  
pp. 3805-3834 ◽  
Author(s):  
Valerio Lembo ◽  
Frank Lunkeit ◽  
Valerio Lucarini
Keyword(s):  
Entropy Production ◽  
Energy Budget ◽  
Diagnostic Tool ◽  
Hydrological Cycle ◽  
Heat Fluxes ◽  
Climate System ◽  
Irreversible Processes ◽  
Energy Budgets ◽  
Energy Cycle ◽  
Lorenz Energy Cycle

Abstract. This work presents the Thermodynamic Diagnostic Tool (TheDiaTo), a novel diagnostic tool for investigating the thermodynamics of climate systems with a wide range of applications, from sensitivity studies to model tuning. It includes a number of modules for assessing the internal energy budget, the hydrological cycle, the Lorenz energy cycle and the material entropy production. The routine takes as inputs energy fluxes at the surface and at the top of the atmosphere (TOA), which allows for the computation of energy budgets at the TOA, the surface and in the atmosphere as a residual. Meridional enthalpy transports are also computed from the divergence of the zonal mean energy budget from which the location and intensity of the maxima in each hemisphere are calculated. Rainfall, snowfall and latent heat fluxes are received as inputs for computation of the water mass and latent energy budgets. If a land–sea mask is provided, the required quantities are separately computed over continents and oceans. The diagnostic tool also computes the annual Lorenz energy cycle (LEC) and its storage and conversion terms by hemisphere and as a global mean. This is computed from three-dimensional daily fields of horizontal wind velocity and temperature in the troposphere. Two methods have been implemented for the computation of the material entropy production: one relying on the convergence of radiative heat fluxes in the atmosphere (indirect method) and the other combining the irreversible processes occurring in the climate system, particularly heat fluxes in the boundary layer, the hydrological cycle and the kinetic energy dissipation as retrieved from the residuals of the LEC (direct method). A version of these diagnostics has been developed as part of the Earth System Model eValuation Tool (ESMValTool) v2.0a1 in order to assess the performances of CMIP6 model simulations, and it will be available in the next release. The aim of this software is to provide a comprehensive picture of the thermodynamics of the climate system, as reproduced in the state-of-the-art coupled general circulation models. This can prove useful for better understanding anthropogenic and natural climate change, paleoclimatic climate variability, and climatic tipping points.

scholarly journals Advances in Understanding the Sea Ice Floe Size Distribution

2021 ◽  
Author(s):  
◽  
Laetitia Roach
Keyword(s):  
Sea Ice ◽  
Size Distribution ◽  
Climate Models ◽  
Arctic Sea Ice ◽  
Climate System ◽  
Model Parameters ◽  
Physical Processes ◽  
Sea Ice Concentration ◽  
Ice Dynamics ◽  
Polar Climate

<p>Sea ice is a critical component of the polar climate system that is tightly coupled to the ocean and atmosphere. It is highly heterogeneous, composed of discrete floes which range in size across space and time. In this thesis, I use a combination of modelling and observational approaches to investigate how different physical processes determine the distribution of sea ice floe sizes. I construct the first global model that simulates floe sizes arising from the interaction of different physical processes. Floe sizes are modified by lateral melt, lateral growth, freezing together of floes and wave-ice interactions. By grounding process descriptions in underlying physics, observations of individual processes can be used to constrain model parameters. In light of the sparseness of floe size observations, I developed a novel methodology to constrain previously-unobserved floe freezing processes from in-situ observations. Results from global coupled sea ice–ocean model simulations are used to quantify the relative impacts of different processes on spatial and seasonal variability in the floe size distribution, providing hypotheses that could be tested by observational campaigns in the future. Under transient historical forcing, the model suggests that the fragmentation of Arctic sea ice has significantly increased over the satellite era.  I also seek to improve understanding of feedbacks between sea ice floe size and the polar climate system. A fragmented ice cover exposes more ice area on the sides of floes to the ocean than sheet ice, promoting lateral melt, which reduces surface albedo. Conducting a statistical analysis of current climate models shows that inclusion of a lateral melt parametrization improves simulation of sea ice concentration relative to observations. However, calculation of lateral melt using the model for prognostic simulation of the sub-grid-scale floe size distribution results in little or no enhancement of lateral melt at a hemispheric scale compared to a simple parametrization, although it is likely to be important at smaller spatial and shorter temporal scales. The new model opens up the possibility of coupling sea ice and ocean surface wave models and of including floe size dependence in other processes, such as form drag, sea ice dynamics, ocean eddies and ocean–atmosphere heat transfer, which may result in significant impacts for polar climate.</p>

scholarly journals Advances in Understanding the Sea Ice Floe Size Distribution

2021 ◽  
Author(s):  
◽  
Laetitia Roach
Keyword(s):  
Sea Ice ◽  
Size Distribution ◽  
Climate Models ◽  
Arctic Sea Ice ◽  
Climate System ◽  
Model Parameters ◽  
Physical Processes ◽  
Sea Ice Concentration ◽  
Ice Dynamics ◽  
Polar Climate

<p>Sea ice is a critical component of the polar climate system that is tightly coupled to the ocean and atmosphere. It is highly heterogeneous, composed of discrete floes which range in size across space and time. In this thesis, I use a combination of modelling and observational approaches to investigate how different physical processes determine the distribution of sea ice floe sizes. I construct the first global model that simulates floe sizes arising from the interaction of different physical processes. Floe sizes are modified by lateral melt, lateral growth, freezing together of floes and wave-ice interactions. By grounding process descriptions in underlying physics, observations of individual processes can be used to constrain model parameters. In light of the sparseness of floe size observations, I developed a novel methodology to constrain previously-unobserved floe freezing processes from in-situ observations. Results from global coupled sea ice–ocean model simulations are used to quantify the relative impacts of different processes on spatial and seasonal variability in the floe size distribution, providing hypotheses that could be tested by observational campaigns in the future. Under transient historical forcing, the model suggests that the fragmentation of Arctic sea ice has significantly increased over the satellite era.  I also seek to improve understanding of feedbacks between sea ice floe size and the polar climate system. A fragmented ice cover exposes more ice area on the sides of floes to the ocean than sheet ice, promoting lateral melt, which reduces surface albedo. Conducting a statistical analysis of current climate models shows that inclusion of a lateral melt parametrization improves simulation of sea ice concentration relative to observations. However, calculation of lateral melt using the model for prognostic simulation of the sub-grid-scale floe size distribution results in little or no enhancement of lateral melt at a hemispheric scale compared to a simple parametrization, although it is likely to be important at smaller spatial and shorter temporal scales. The new model opens up the possibility of coupling sea ice and ocean surface wave models and of including floe size dependence in other processes, such as form drag, sea ice dynamics, ocean eddies and ocean–atmosphere heat transfer, which may result in significant impacts for polar climate.</p>

scholarly journals Toward Quantifying the Climate Heat Engine: Solar Absorption and Terrestrial Emission Temperatures and Material Entropy Production

2017 ◽  
Vol 74 (6) ◽  
pp. 1721-1734 ◽  
Author(s):  
Peter R. Bannon ◽  
Sukyoung Lee
Keyword(s):  
Steady State ◽  
Radiative Transfer ◽  
Entropy Production ◽  
Climate Models ◽  
Heat Engine ◽  
Climate System ◽  
Solar Absorption ◽  
Maximum Production ◽  
Change Material

Abstract A heat-engine analysis of a climate system requires the determination of the solar absorption temperature and the terrestrial emission temperature. These temperatures are entropically defined as the ratio of the energy exchanged to the entropy produced. The emission temperature, shown here to be greater than or equal to the effective emission temperature, is relatively well known. In contrast, the absorption temperature requires radiative transfer calculations for its determination and is poorly known. The maximum material (i.e., nonradiative) entropy production of a planet’s steady-state climate system is a function of the absorption and emission temperatures. Because a climate system does no work, the material entropy production measures the system’s activity. The sensitivity of this production to changes in the emission and absorption temperatures is quantified. If Earth’s albedo does not change, material entropy production would increase by about 5% per 1-K increase in absorption temperature. If the absorption temperature does not change, entropy production would decrease by about 4% for a 1% decrease in albedo. It is shown that, as a planet’s emission temperature becomes more uniform, its entropy production tends to increase. Conversely, as a planet’s absorption temperature or albedo becomes more uniform, its entropy production tends to decrease. These findings underscore the need to monitor the absorption temperature and albedo both in nature and in climate models. The heat-engine analyses for four planets show that the planetary entropy productions are similar for Earth, Mars, and Titan. The production for Venus is close to the maximum production possible for fixed absorption temperature.

scholarly journals The Flexible Ocean and Climate Infrastructure version 1 (FOCI1): mean state and variability

2020 ◽  
Vol 13 (6) ◽  
pp. 2533-2568 ◽  
Author(s):  
Katja Matthes ◽  
Arne Biastoch ◽  
Sebastian Wahl ◽  
Jan Harlaß ◽  
Torge Martin ◽  
...  
Keyword(s):  
Sea Ice ◽  
Land Surface ◽  
General Circulation ◽  
Climate Models ◽  
Weather Prediction ◽  
Circulation Model ◽  
Meridional Overturning Circulation ◽  
Climate System ◽  
Surface Model ◽  
Model Components

Abstract. A new Earth system model, the Flexible Ocean and Climate Infrastructure (FOCI), is introduced. A first version of FOCI consists of a global high-top atmosphere (European Centre Hamburg general circulation model; ECHAM6.3) and an ocean model (Nucleus for European Modelling of the Ocean v3.6; NEMO3.6) as well as sea-ice (Louvain-la-Neuve sea Ice Model version 2; LIM2) and land surface model components (Jena Scheme for Biosphere Atmosphere Coupling in Hamburg; JSBACH), which are coupled through the OASIS3-MCT software package. FOCI includes a number of optional modules which can be activated depending on the scientific question of interest. In the atmosphere, interactive stratospheric chemistry can be used (ECHAM6-HAMMOZ) to study, for example, the effects of the ozone hole on the climate system. In the ocean, a biogeochemistry model (Model of Oceanic Pelagic Stoichiometry; MOPS) is available to study the global carbon cycle. A unique feature of FOCI is the ability to explicitly resolve mesoscale ocean eddies in specific regions. This is realized in the ocean through nesting; first examples for the Agulhas Current and the Gulf Stream systems are described here. FOCI therefore bridges the gap between coarse-resolution climate models and global high-resolution weather prediction and ocean-only models. It allows to study the evolution of the climate system on regional and seasonal to (multi)decadal scales. The development of FOCI resulted from a combination of the long-standing expertise in ocean and climate modeling in several research units and divisions at the Helmholtz Centre for Ocean Research Kiel (GEOMAR). FOCI will thus be used to complement and interpret long-term observations in the Atlantic, enhance the process understanding of the role of mesoscale oceanic eddies for large-scale oceanic and atmospheric circulation patterns, study feedback mechanisms with stratospheric processes, estimate future ocean acidification, and improve the simulation of the Atlantic Meridional Overturning Circulation changes and their influence on climate, ocean chemistry and biology. In this paper, we present both the scientific vision for the development of FOCI as well as some technical details. This includes a first validation of the different model components using several configurations of FOCI. Results show that the model in its basic configuration runs stably under pre-industrial control as well as under historical forcing and produces a mean climate and variability which compares well with observations, reanalysis products and other climate models. The nested configurations reduce some long-standing biases in climate models and are an important step forward to include the atmospheric response in multidecadal eddy-rich configurations.

scholarly journals A seamless approach to understanding and predicting Arctic sea ice in Met Office modelling systems

2015 ◽  
Vol 373 (2045) ◽  
pp. 20140161 ◽  
Author(s):  
Helene T. Hewitt ◽  
Jeff K. Ridley ◽  
Ann B. Keen ◽  
Alex E. West ◽  
K. Andrew Peterson ◽  
...  
Keyword(s):  
Sea Ice ◽  
Seasonal Cycle ◽  
Climate Models ◽  
Early Summer ◽  
Arctic Sea Ice ◽  
Heat Fluxes ◽  
Cmip5 Models ◽  
Energy Budgets ◽  
Arctic Sea ◽  
Use Of Models

Recent CMIP5 models predict large losses of summer Arctic sea ice, with only mitigation scenarios showing sustainable summer ice. Sea ice is inherently part of the climate system, and heat fluxes affecting sea ice can be small residuals of much larger air–sea fluxes. We discuss analysis of energy budgets in the Met Office climate models which point to the importance of early summer processes (such as clouds and meltponds) in determining both the seasonal cycle and the trend in ice decline. We give examples from Met Office modelling systems to illustrate how the seamless use of models for forecasting on time scales from short range to decadal might help to unlock the drivers of high latitude biases in climate models.

scholarly journals Observation-based selection of climate models projects Arctic ice-free summers around 2035

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
David Docquier ◽  
Torben Koenigk
Keyword(s):  
Model Selection ◽  
Sea Ice ◽  
Climate Models ◽  
Global Climate ◽  
Coupled Model ◽  
Arctic Sea Ice ◽  
Global Climate Models ◽  
The Arctic ◽  
Arctic Sea ◽  
Area And Volume

AbstractArctic sea ice has been retreating at an accelerating pace over the past decades. Model projections show that the Arctic Ocean could be almost ice free in summer by the middle of this century. However, the uncertainties related to these projections are relatively large. Here we use 33 global climate models from the Coupled Model Intercomparison Project 6 (CMIP6) and select models that best capture the observed Arctic sea-ice area and volume and northward ocean heat transport to refine model projections of Arctic sea ice. This model selection leads to lower Arctic sea-ice area and volume relative to the multi-model mean without model selection and summer ice-free conditions could occur as early as around 2035. These results highlight a potential underestimation of future Arctic sea-ice loss when including all CMIP6 models.

scholarly journals Observations and Simulations of Meteorological Conditions over Arctic Thick Sea Ice in Late Winter during the Transarktika 2019 Expedition

Atmosphere ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 174
Author(s):  
Günther Heinemann ◽  
Sascha Willmes ◽  
Lukas Schefczyk ◽  
Alexander Makshtas ◽  
Vasilii Kustov ◽  
...  
Keyword(s):  
Sea Ice ◽  
Climate Models ◽  
Climate Model ◽  
Regional Climate ◽  
Open Water ◽  
The Arctic ◽  
Late Winter ◽  
Good Representation ◽  
Hourly Temperature ◽  
Ice Model

The parameterization of ocean/sea-ice/atmosphere interaction processes is a challenge for regional climate models (RCMs) of the Arctic, particularly for wintertime conditions, when small fractions of thin ice or open water cause strong modifications of the boundary layer. Thus, the treatment of sea ice and sub-grid flux parameterizations in RCMs is of crucial importance. However, verification data sets over sea ice for wintertime conditions are rare. In the present paper, data of the ship-based experiment Transarktika 2019 during the end of the Arctic winter for thick one-year ice conditions are presented. The data are used for the verification of the regional climate model COSMO-CLM (CCLM). In addition, Moderate Resolution Imaging Spectroradiometer (MODIS) data are used for the comparison of ice surface temperature (IST) simulations of the CCLM sea ice model. CCLM is used in a forecast mode (nested in ERA5) for the Norwegian and Barents Seas with 5 km resolution and is run with different configurations of the sea ice model and sub-grid flux parameterizations. The use of a new set of parameterizations yields improved results for the comparisons with in-situ data. Comparisons with MODIS IST allow for a verification over large areas and show also a good performance of CCLM. The comparison with twice-daily radiosonde ascents during Transarktika 2019, hourly microwave water vapor measurements of first 5 km in the atmosphere and hourly temperature profiler data show a very good representation of the temperature, humidity and wind structure of the whole troposphere for CCLM.

Constraining Neoproterozoic subtropical low-level clouds to assess the plausibility of near-Snowball Earth states

2021 ◽  
Author(s):  
Christoph Braun ◽  
Aiko Voigt ◽  
Johannes Hörner ◽  
Joaquim G. Pinto
Keyword(s):  
Sea Ice ◽  
Climate Models ◽  
Global Climate ◽  
Global Climate Models ◽  
Mixed Phase ◽  
Snowball Earth ◽  
Stable Range ◽  
Climate Regime ◽  
Low Level ◽  
Mixed Phase Clouds

&lt;p&gt;Stable waterbelt climate states with close to global ice cover challenge the classical Snowball Earth hypothesis because they provide a robust explanation for the survival of advanced marine species during the Neoproterozoic glaciations (1000 &amp;#8211; 541 Million years ago). Whether Earth&amp;#8217;s climate stabilizes in a waterbelt state or rushes towards a Snowball state is determined by the magnitude of the ice-albedo feedback in the subtropics, where dark, bare sea ice instead of snow-covered sea ice prevails. For a given bare sea-ice albedo, the subtropical ice-albedo feedback and thus the stable range of the waterbelt climate regime is sensitive to the albedo over ice-free ocean, which is largely determined by shortwave cloud-radiative effects (CRE). In the present-day climate, CRE are known to dominate the spread of climate sensitivity across global climate models. We here study the impact of uncertainty associated with CRE on the existence of geologically relevant waterbelt climate regimes using two global climate models and an idealized energy balance model. We find that the stable range of the waterbelt climate regime is very sensitive to the abundance of subtropical low-level mixed-phase clouds. If subtropical cloud cover is low, climate sensitivity becomes so high as to inhibit stable waterbelt states.&lt;/p&gt;&lt;p&gt;The treatment of mixed-phase clouds is highly uncertain in global climate models. Therefore we aim to constrain the uncertainty associated with their CRE by means of a hierarchy of global and regional simulations that span horizontal grid resolutions from 160 km to 300m, and in particular include large eddy simulations of subtropical mixed-phase clouds located over a low-latitude ice edge. In the cold waterbelt climate subtropical CRE arise from convective events caused by strong meridional temperature gradients and stratocumulus decks located in areas of large-scale descending motion. We identify the latter to dominate subtropical CRE and therefore focus our large eddy simulations on subtropical stratocumulus clouds. By conducting simulations with two extreme scenarios for the abundance of atmospheric mineral dust, which serves as ice-nucleating particles and therefore can control mixed-phase cloud physics, we aim to estimate the possible spread of CRE associated with subtropical mixed-phase clouds. From this estimate we may assess whether Neoproterozoic low-level cloud abundance may have been high enough to sustain a stable waterbelt climate regime.&lt;/p&gt;

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