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Author Topic: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on E3SM/ACME  (Read 31800 times)

AbruptSLR

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The sooner that Earth System model correctly account for interactions and feedbacks with ice sheets, the better:

Fyke, J, O Sergienko, M Lofverstrom, S Price, and J Lenaerts.  2018.  "An Overview of Interactions and Feedbacks Between Ice Sheets and the Earth System."  Reviews of Geophysics, doi:10.1029/2018rg000600.

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018RG000600

Abstract: "Ice sheet response to forced changes—such as that from anthropogenic climate forcing—is closely regulated by two‐way interactions with other components of the Earth system. These interactions encompass the ice sheet response to Earth system forcing, the Earth system response to ice sheet change, and feedbacks resulting from coupled ice sheet/Earth system evolution. Motivated by the impact of Antarctic and Greenland ice sheet change on future sea level rise, here we review the state of knowledge of ice sheet/Earth system interactions and feedbacks. We also describe emerging observation and model‐based methods that can improve understanding of ice sheet/Earth system interactions and feedbacks. We particularly focus on the development of Earth system models that incorporate current understanding of Earth system processes, ice dynamics, and ice sheet/Earth system couplings. Such models will be critical tools for projecting future sea level rise from anthropogenically forced ice sheet mass loss."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

jacksmith4tx

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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on E3SM/ACME
« Reply #201 on: August 04, 2018, 01:35:38 AM »
Judith Curry occasionally post a list of climate relate research and news articles and today I spotted something interesting. In this case it was building Artificial Intelligence climate models. AI is one of my favorite areas of science research and especially when it applies to climate change.
A group of private donors have committed to funding a major effort to apply state-of-the-art AI and machine learning to create a high resolution model that will include an experimental cloud simulator in addition to extensive observational data from the atmosphere, oceans, land use and biosphere feedback. One to keep an eye on.

Welcome to the EARTH MACHINE:
http://www.sciencemag.org/news/2018/07/science-insurgents-plot-climate-model-driven-artificial-intelligence
Science is a thought process, technology will change reality.

AbruptSLR

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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on E3SM/ACME
« Reply #202 on: August 04, 2018, 06:58:30 PM »
Newly identified evidence indicates that the Southern Ocean will likely stop absorbing as much CO₂ as it recently has been doing, with continuing anthropogenic radiative forcing:

Title: "How much longer will Southern Ocean slow climate change?"

http://www.newstalkzb.co.nz/news/national/how-much-longer-will-southern-ocean-slow-climate-change/

Extract: "The vast and wild ocean current sucks up more than 40 per cent of the carbon dioxide we produce, acting as a temporary climate-change buffer by slowing down the accumulation of greenhouse gases in our atmosphere.

Yet the same westerly winds that play a critical role in regulating its storing capacity are now threatening its future as a CO2 bank, by bringing deep carbon-rich waters up to the surface.
Many climate models predict that the westerly winds overlying the ocean would get stronger if atmospheric greenhouse gas concentrations continued to risk.

A new international study suggests that in the past, strong westerlies have been linked to higher levels of atmospheric CO2 due to their impact on the Southern Ocean carbon balance.

That meant stronger westerlies could actually speed up climate change if mankind continued to emit as much CO2 as it does today.

"Our new records of the Southern Hemisphere westerly winds suggest there have been large changes in wind intensity over the past 12,000 years.

"This is in marked contrast to climate model simulations that predict only relatively small wind speed changes over the same period."

Yet, Mikaloff-Fletcher added, sea surface carbon data suggested that there was a reversal of this trend in the early 2000s, when the Southern Ocean began taking up carbon much more quickly, even though the westerlies didn't slow.

"The mechanisms behind this change still aren't fully explained, which makes it hard to predict whether this is a short-term effect or a long-term one," she said.

"The Macquarie study suggests that the sudden increase in Southern Ocean carbon uptake may not persist on longer timescales.""
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on E3SM/ACME
« Reply #203 on: August 10, 2018, 02:32:46 PM »
Offshore methane seeps from hydrates is a 'difficult but important scientific problem'.  The linked article discusses new research of how underwater audio microphones can continuously monitor the size of methane bubbles escaping from such seeps.  This better enables scientists to differentiate (attribute causality) the influence of various factors (such as earthquakes, or submarine landslides) that change the rate of methane releases from this enormous source of currently sequestered methane:

Title: "Audio Reveals Sizes of Methane Bubbles Rising from the Seafloor"

https://eos.org/articles/audio-reveals-sizes-of-methane-bubbles-rising-from-the-seafloor?utm_source=eos&utm_medium=email&utm_campaign=EosBuzz081018

Extract: "A sensitive underwater microphone captures the sounds of methane, a potent greenhouse gas, escaping into waters off the coast of Oregon. Using this sound, researchers can estimate the bubbles’ sizes.

“Earthquakes potentially give new pathways for methane to rise up,” said Tamara Baumberger, a marine geochemist at Oregon State University and the National Oceanic and Atmospheric Administration in Newport, Ore. That gas can have positive and negative effects. Methane seeps are often sites of rich ecosystems that include microbes, crabs, and clams, but the escaping gas can also contribute to ocean acidification, said Baumberger.

And the number of known methane seeps is increasing exponentially, said H. Paul Johnson, a marine geophysicist at the University of Washington in Seattle who was not involved in the research. Therefore, quantifying how much methane is escaping from the seafloor is a “difficult but important scientific problem,” he said, noting that scientists are still working on accurately estimating the number of methane seeps and the rate at which gas is escaping from them.

Audio measurements could fundamentally help."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on E3SM/ACME
« Reply #204 on: August 14, 2018, 11:25:45 PM »
The linked reference indicates that: "… climate models suggests that about half of the model uncertainty in the mid-latitude cloud-circulation coupling stems from this impact of the circulation on the large-scale temperature structure of the atmosphere, and thus could be removed by improving the climatological circulation in models. This illustrates how understanding of large-scale dynamics can help reduce uncertainty in clouds and their response to climate change."

Lipat, B.R., A. Voigt, G. Tselioudis, and L.M. Polvani (2018), "Model uncertainty in cloud-circulation coupling, and cloud-radiative response to increasing CO2, linked to biases in climatological circulation", J. Climate, doi:10.1175/JCLI-D-17-0665.1.

https://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-17-0665.1

Abstract: "Recent analyses of global climate models suggest that uncertainty in the coupling between mid-latitude clouds and the atmospheric circulation contributes to uncertainty in climate sensitivity. However, the reasons behind model differences in the cloud-circulation coupling have remained unclear. Here, we use a global climate model in idealized aquaplanet setup to show that the Southern Hemisphere climatological circulation, which in many models is biased equatorward, contributes to the model differences in the cloud-circulation coupling. For the same poleward shift of the Hadley circulation (HC) edge, models with narrower climatological HCs exhibit stronger mid-latitude cloud-induced shortwave warming than models with wider climatological HCs. This cloud-induced radiative warming results predominantly from a subsidence warming that decreases cloud fraction and is stronger for narrower HCs because of a larger meridional gradient in the vertical velocity. A comparison of our aquaplanet results with comprehensive climate models suggests that about half of the model uncertainty in the mid-latitude cloud-circulation coupling stems from this impact of the circulation on the large-scale temperature structure of the atmosphere, and thus could be removed by improving the climatological circulation in models. This illustrates how understanding of large-scale dynamics can help reduce uncertainty in clouds and their response to climate change."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on E3SM/ACME
« Reply #205 on: August 15, 2018, 05:43:18 PM »
Essentially, this reference acknowledges that current SLR projections are incomplete, and discusses means to improve those existing SLR projections:

Fyke, J, O Sergienko, M Lofverstrom, S Price, and J Lenaerts.  2018.  "An Overview of Interactions and Feedbacks Between Ice Sheets and the Earth System."  Reviews of Geophysics, doi:10.1029/2018rg000600.

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018RG000600

Abstract: "Ice sheet response to forced changes—such as that from anthropogenic climate forcing—is closely regulated by two‐way interactions with other components of the Earth system. These interactions encompass the ice sheet response to Earth system forcing, the Earth system response to ice sheet change, and feedbacks resulting from coupled ice sheet/Earth system evolution. Motivated by the impact of Antarctic and Greenland ice sheet change on future sea level rise, here we review the state of knowledge of ice sheet/Earth system interactions and feedbacks. We also describe emerging observation and model‐based methods that can improve understanding of ice sheet/Earth system interactions and feedbacks. We particularly focus on the development of Earth system models that incorporate current understanding of Earth system processes, ice dynamics, and ice sheet/Earth system couplings. Such models will be critical tools for projecting future sea level rise from anthropogenically forced ice sheet mass loss."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on E3SM/ACME
« Reply #206 on: August 15, 2018, 06:09:18 PM »
Future freshwater exports from the Arctic into the North Atlantic can come several sources including: a) the Beaufort Gyre, b) melting Arctic Sea Ice and c) ice mass loss from the Greenland Ice Sheet.  Furthermore, this Arctic freshwater can follow different pathways, and the cited reference indicates that these different pathways would have different (but significant) impacts on both the North Atlantic Convection and on the AMOC.  This research provide insights into Hansen's ice-climate feedback mechanism:

Wang, He, Sonya Legg, and Robert Hallberg, July 2018: The Effect of Arctic Freshwater Pathways on North Atlantic Convection and the Atlantic Meridional Overturning Circulation. Journal of Climate, 31(13), DOI:10.1175/JCLI-D-17-0629.1 .

https://journals.ametsoc.org/doi/10.1175/JCLI-D-17-0629.1
&
https://journals.ametsoc.org/doi/pdf/10.1175/JCLI-D-17-0629.1

Abstract: "This study examines the relative roles of the Arctic freshwater exported via different pathways on deep convection in the North Atlantic and the Atlantic meridional overturning circulation (AMOC). Deep water feeding the lower branch of the AMOC is formed in several North Atlantic marginal seas, including the Labrador Sea, Irminger Sea, and the Nordic seas, where deep convection can potentially be inhibited by surface freshwater exported from the Arctic. The sensitivity of the AMOC and North Atlantic to two major freshwater pathways on either side of Greenland is studied using numerical experiments. Freshwater export is rerouted in global coupled climate models by blocking and expanding the channels along the two routes. The sensitivity experiments are performed in two sets of models (CM2G and CM2M) with different control simulation climatology for comparison. Freshwater via the route east of Greenland is found to have a larger direct impact on Labrador Sea convection. In response to the changes of freshwater route, North Atlantic convection outside of the Labrador Sea changes in the opposite sense to the Labrador Sea. The response of the AMOC is found to be sensitive to both the model formulation and mean-state climate."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on E3SM/ACME
« Reply #207 on: August 15, 2018, 06:28:46 PM »
The linked report summarizes modeling work for the Arctic System Reanalysis Version 2:

Bromwich, D., A. Wilson, L. Bai, Z. Liu, M. Barlage, C. Shih, S. Maldonado, K. Hines, S.-H. Wang, J. Woollen, B. Kuo, H. Lin, T. Wee, M. Serreze, and J. Walsh, 2018: The Arctic System Reanalysis Version 2. Bull. Amer. Meteor. Soc., 99, 805-828, doi: 10.1175/BAMS-D-16-0215.1.

http://polarmet.osu.edu/PMG_publications/bromwich_wilson_bams_2018.pdf

“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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AbruptSLR

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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on E3SM/ACME
« Reply #208 on: August 15, 2018, 06:50:35 PM »
The two linked references provide new paleo information that is useful for calibrating state-of-the-art ESMs with regard to the likelihood of future: a) CO₂ fluxes into the atmosphere from deep Pacific Ocean waters and b) changes in the marine nitrogen cycles and the emergence of anoxic marine conditions.

Jianghui Du et al. (2018), "Flushing of the deep Pacific Ocean and the deglacial rise of atmospheric CO2 concentrations", Nature Geoscience, 1–7; doi: https://doi.org/10.1038/s41561-018-0205-6

http://www.nature.com/articles/s41561-018-0205-6

Extract: "Enhanced overturning in the Pacific Ocean flushed carbon from the abyssal ocean to the atmosphere during the last deglaciation, according to authigenic neodymium isotope data."

&

 Christopher K. Junium, Alexander J. Dickson & Benjamin T. Uveges (2018), "Perturbation to the nitrogen cycle during rapid Early Eocene global warming", Nature Communications 9, 3186; doi: https://doi.org/10.1038/s41467-018-05486-w

http://www.nature.com/articles/s41467-018-05486-w

 Extract: "Studying the PETM, a past period of rapid warming ~56 Ma, could provide insights into ecosystem response under future warming conditions. Here, the authors present stable nitrogen isotope data that reveal a dramatic change in the marine nitrogen cycle and the emergence of anoxic conditions."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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mitch

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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on E3SM/ACME
« Reply #209 on: August 15, 2018, 08:01:51 PM »
There is one other pathway for freshwater to be exported: down. Mixing by storms in the summer time can exchange relatively fresh surface water with saltier Atlantic water at depth. This also increases the heat reservoir needed to be overcome in fall/winter for ice to form. 

AbruptSLR

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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on E3SM/ACME
« Reply #210 on: August 15, 2018, 09:06:08 PM »
Given the impact (and increasing probability) of a significant freshwater release from the Beaufort Gyre into the North Atlantic, numerous scientists are actively studying related issues including those cited in the links below:

"Beaufort Gyre Exploration Project"

http://www.whoi.edu/page.do?pid=66456

&

Meneghello G. , J. Marshall, M.-L. Timmermans and J. Scott (2018). Observations of seasonal upwelling and downwelling in the Beaufort Sea mediated by sea ice. J. Phys. Oceanogr., 48, 795–805. doi:10.1175/JPO-D-17-0188.1

https://journals.ametsoc.org/doi/10.1175/JPO-D-17-0188.1

Abstract: "We present observational estimates of Ekman pumping in the Beaufort Gyre region. Averaged over the Canada Basin, the results show a 2003–14 average of 2.3 m yr−1 downward with strong seasonal and interannual variability superimposed: monthly and yearly means range from 30 m yr−1 downward to 10 m yr−1 upward. A clear, seasonal cycle is evident with intense downwelling in autumn and upwelling during the winter months, despite the wind forcing being downwelling favorable year-round. Wintertime upwelling is associated with friction between the large-scale Beaufort Gyre ocean circulation and the surface ice pack and contrasts with previous estimates of yearlong downwelling; as a consequence, the yearly cumulative Ekman pumping over the gyre is significantly reduced. The spatial distribution of Ekman pumping is also modified, with the Beaufort Gyre region showing alternating, moderate upwelling and downwelling, while a more intense, yearlong downwelling averaging 18 m yr−1 is identified in the northern Chukchi Sea region. Implications of the results for understanding Arctic Ocean dynamics and change are discussed."

&

Meneghello, G., J. Marshall, S. Cole, and M.-L. Timmermans (2018). Observational inferences of lateral eddy diffusivity in the halocine of the Beaufort Gyre. Geophys. Res. Lett., 44, 12 331–12 338, https://doi.org/10.1002/2017GL075126.

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1002/2017GL075126

Abstract: "Using Ekman pumping rates mediated by sea ice in the Arctic Ocean's Beaufort Gyre (BG), the magnitude of lateral eddy diffusivities required to balance downward pumping is inferred. In this limit—that of vanishing residual‐mean circulation—eddy‐induced upwelling exactly balances downward pumping. The implied eddy diffusivity varies spatially and decays with depth, with values of 50–400 m2/s. Eddy diffusivity estimated using mixing length theory applied to BG mooring data exhibits a similar decay with depth and range of values from 100 m2/s to more than 600 m2/s. We conclude that eddy diffusivities in the BG are likely large enough to balance downward Ekman pumping, arresting the deepening of the gyre and suggesting that eddies play a zero‐order role in buoyancy and freshwater budgets of the BG."

Note: "Zeroth-order approximation (also 0th order) is the term scientists use for a first educated guess at an answer."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on E3SM/ACME
« Reply #211 on: August 15, 2018, 11:36:58 PM »
Information from the linked reference can be used to help calibrate ESMs to properly account for Hansen's ice-climate feedback mechanism:

Ivanovic RF; Gregoire LJ; Burke A; Wickert AD; Valdes PJ; Ng HC; Robinson LF; McManus JF; Mitrovica JX; Lee L; Dentith JE (2018) Acceleration of northern ice sheet melt induces AMOC slowdown and northern cooling in simulations of the early last deglaciation, Paleoceanography and Paleoclimatology. doi: 10.1029/2017PA003308

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2017PA003308

Abstract
The cause of a rapid change in Atlantic Ocean circulation and northern cooling at the onset of Heinrich Stadial 1 ~18.5 ka is unclear. Previous studies have simulated the event using ice sheet and/or iceberg meltwater forcing, but these idealized freshwater fluxes have been unrealistically large. Here we use a different approach, driving a high‐resolution drainage network model with a recent time‐resolved global paleo‐ice sheet reconstruction to generate a realistic meltwater forcing. We input this flux to the Hadley Centre Coupled Model version 3 (HadCM3) climate model without adjusting the timing or amplitude and find that an acceleration in northern ice sheet melting (up to ~7.5 m/kyr global mean sea level rise equivalent) triggers a 20% reduction in the Atlantic Meridional Overturning Circulation. The simulated pattern of ocean circulation and climate change matches an array of paleoclimate and ocean circulation reconstructions for the onset of Heinrich Stadial 1, in terms of both rates and magnitude of change. This is achieved with a meltwater flux that matches constraints on sea level changes and ice sheet evolution around 19–18 ka. Since the rates of melting are similar to those projected for Greenland by 2200, constraining the melt rates and magnitude of climate change during Heinrich Stadial 1 would provide an important test of climate model sensitivity to future ice sheet melt.

Plain Language Summary
Atlantic Ocean circulation plays a key role in redistributing heat around Earth's surface, and thus has an important influence on our climate. Because of this, sudden shifts in Atlantic Ocean circulation can drive rapid climate changes. One such example is at the onset of “Heinrich Stadial 1”, 18.5 thousand years ago, when geological records show that Atlantic circulation weakened and the Northern Hemisphere cooled while the Southern Hemisphere warmed. At the time, huge ice sheets (several kilometers thick) covered much of North America and northern Europe. Climate model results suggest that the freshwater produced by these melting ice sheets is responsible for weakening the Atlantic Ocean circulation and triggering the abrupt climate changes captured in the geological records. This result helps to elucidate the complex interaction between ice sheets, ocean circulation, and climate, and how these interactions can lead to sudden shifts in climates of the past and, potentially, the future. Indeed, the rate of melting we adopt in the present model is comparable to the melting projected for the Greenland Ice Sheet by 2200.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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AbruptSLR

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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on E3SM/ACME
« Reply #212 on: August 16, 2018, 12:24:43 AM »
Data cited in the linked reference can be used to better calibrate ESMs:

Sebastian G. Mutz et al. (2018), "Estimates of late Cenozoic climate change relevant to Earth surface processes in tectonically active orogens", Earth Surf. Dynam., 6, 271–301, https://doi.org/10.5194/esurf-6-271-2018

https://www.earth-surf-dynam.net/6/271/2018/esurf-6-271-2018.pdf

Abstract. The denudation history of active orogens is often interpreted in the context of modern climate gradients. Here we address the validity of this approach and ask what are the spatial and temporal variations in palaeoclimate for a latitudinally diverse range of active orogens? We do this using high-resolution (T159, ca. 80x80 km at the Equator) palaeoclimate simulations from the ECHAM5 global atmospheric general circulation model and a statistical cluster analysis of climate over different orogens (Andes, Himalayas, SE Alaska, Pacific NW USA). Time periods and boundary conditions considered include the Pliocene (PLIO, ~3 Ma), the Last Glacial Maximum (LGM, ~21 ka), mid-Holocene (MH, ~6 ka), and pre-industrial (PI, reference year 1850). The regional simulated climates of each orogen are described by means of cluster analyses based on the variability in precipitation, 2m air temperature, the intra-annual amplitude of these values, and monsoonal wind speeds where appropriate. Results indicate the largest differences in the PI climate existed for the LGM and PLIO climates in the form of widespread cooling and reduced precipitation in the LGM and warming and enhanced precipitation during the PLIO. The LGM climate shows the largest deviation in annual precipitation from the PI climate and shows enhanced precipitation in the temperate Andes and coastal regions for both SE Alaska and the US Pacific Northwest. Furthermore, LGM precipitation is reduced in the western Himalayas and enhanced in the eastern Himalayas, resulting in a shift of the wettest regional climates eastward along the orogen. The cluster-analysis results also suggest more climatic variability across latitudes east of the Andes in the PLIO climate than in other time slice experiments conducted here. Taken together, these results highlight significant changes in late Cenozoic regional climatology over the last ~3 Myr. Comparison of simulated climate with proxy-based reconstructions for the MH and LGM reveal satisfactory to good performance of the model in reproducing precipitation changes, although in some cases discrepancies between neighbouring proxy observations highlight contradictions between proxy observations themselves. Finally, we document regions where the largest magnitudes of late Cenozoic changes in precipitation and temperature occur and offer the highest potential for future observational studies that quantify the impact of climate change on denudation and weathering rates.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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AbruptSLR

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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on E3SM/ACME
« Reply #213 on: August 17, 2018, 07:30:05 PM »
The linked reference can be used to better calibrate advanced ESMs:

P. Bakker & M. Prange (03 August 2018), "Response of the Intertropical Convergence Zone to Antarctic Ice Sheet melt", Geophysical Research Letters, https://doi.org/10.1029/2018GL078659

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018GL078659

Abstract: "Past cooling events in the Northern Hemisphere have been shown to impact the location of the intertropical convergence zone (ITCZ) and therewith induce a southward shift of tropical precipitation. Here we use high‐resolution coupled ocean‐atmosphere simulations to show that reasonable past melt rates of the Antarctic Ice Sheet can similarly have led to shifts of the ITCZ, albeit in opposite direction, through large‐scale surface air temperature changes over the Southern Ocean. Through sensitivity experiments employing slightly negative to large positive meltwater fluxes we deduce that meridional shifts of the Hadley cell and therewith the ITCZ are, to a first order, a linear response to Southern Hemisphere high‐latitude surface air temperature changes and Antarctic Ice Sheet melt rates. This highlights the possibility to use past episodes of anomalous melt rates to better constrain a possible future response of low latitude precipitation to continued global warming and a shrinking Antarctic Ice Sheet."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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AbruptSLR

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Re: Climate Model Test Beds: Calibrating Nonlinear ESMs focused on E3SM/ACME
« Reply #214 on: August 17, 2018, 07:35:44 PM »
Findings of the linked reference can be used to better calibrate advanced ESMs:

Schröder, D., Feltham, D. L., Tsamados, M., Ridout, A., and Tilling, R.: New insight from CryoSat-2 sea ice thickness for sea ice modelling, The Cryosphere Discuss., https://doi.org/10.5194/tc-2018-159, in review, 2018.

https://www.the-cryosphere-discuss.net/tc-2018-159/

Abstract. Estimates of Arctic sea ice thickness are available from the CryoSat-2 (CS2) radar altimetry mission during ice growth seasons since 2010. We derive the sub-grid scale ice thickness distribution (ITD) with respect to 5 ice thickness categories used in a sea ice component (CICE) of climate simulations. This allows us to initialize the ITD in stand-alone simulations with CICE and to verify the simulated cycle of ice thickness. We find that a default CICE simulation strongly underestimates ice thickness, despite reproducing the inter-annual variability of summer sea ice extent. We can identify the underestimation of winter ice growth as being responsible and show that increasing the ice conductive flux for lower temperatures (bubbly brine scheme) and accounting for the loss of drifting snow results in the simulated sea ice growth being more realistic. Sensitivity studies provide insight into the impact of initial and atmospheric conditions and, thus, on the role of positive and negative feedback processes. During summer, atmospheric conditions are responsible for 50% of September sea ice thickness variability through the positive sea ice and melt pond albedo feedback. However, atmospheric winter conditions have little impact on winter ice growth due to the dominating negative conductive feedback process: the thinner the ice and snow in autumn, the stronger the ice growth in winter. We conclude that the fate of Arctic summer sea ice is largely controlled by atmospheric conditions during the melting season rather than by winter temperature. Our optimal model configuration does not only improve the simulated sea ice thickness, but also summer sea ice concentration, melt pond fraction, and length of the melt season. It is the first time CS2 sea ice thickness data have been applied successfully to improve sea ice model physics.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson