Statistical approaches and tools for IntCal20

2020 ◽  
Author(s):  
Christopher Bronk Ramsey ◽  
Timothy Heaton ◽  
Maarten Blaauw ◽  
Paul Blackwell ◽  
Paula Reimer ◽  
...  
Keyword(s):  
Calibration Curve ◽  
General Circulation ◽  
Large Scale ◽  
Ice Core ◽  
Short Note ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Cosmogenic Radionuclides ◽  
Statistical Approaches ◽  
First Time

<p>The construction of the new IntCal20 calibration curve was undertaken using a number of new statistical approaches (Heaton et al. 2020), when compared to previous versions.  This was partly due to the nature of some of the new datasets; partly to improve the robustness of the curve; and partly to address particular aspects of radiocarbon within the Earth System such as reservoir effects, incorporation of geological carbon in speleothems, and the uncertainties associated with different timescales.  Here the main approaches taken are summarised with a perspective on their strengths and potential weaknesses.</p><p>In particular, the high-resolution extensions to the Hulu speleothem radiocarbon record (Cheng et al. 2018) allow it to be used to anchor the chronology for other key records (Suigetsu, Cariaco, and the Pakistan and Iberian Margins), providing a coherence in the timescale not possible before.  Further, for the first time, we incorporate time varying marine reservoir ages, constrained by the Hamburg Large Scale Geostrophic Ocean General Circulation Model (LSG OGCM)(Butzin et al. 2020).  In addition, work on the relationship to the Greenland ice core timescales (Adolphi et al. 2018) enables us to make direct comparison between radiocarbon dated records and the ice core timescale and here we report on tools to assist with this.</p><p>Along with the update to the calibration curve itself, the associated tools for calibration, age-depth modelling and Bayesian modelling have also been updated to make best use of the new resolution and characteristics of the curve.  Here we summarise updates to Bacon, Calib and OxCal.</p><p>Heaton, TJ. et al (2020) The IntCal20 approach to radiocarbon calibration curve construction: A new methodology using Bayesian splines and errors-in-variables Radiocarbon: in review.</p><p>Cheng, H. et al. (2018) Atmospheric 14C/12C changes during the last glacial period from Hulu Cave. Science, 362(6420), pp.1293-1297. doi:10.1126/science.aau0747</p><p>Adolphi, F. et al. (2018) Connecting the Greenland ice-core and U/Th timescales via cosmogenic radionuclides: Testing the synchronicity of Dansgaard-Oeschger events. Climate of the Past, 14, pp.1755-1781. doi:10.5194/cp-2018-85</p><p>Butzin, M. et al. (2020) A short note on marine reservoir age simulations used in IntCal20. Radiocarbon: in press.</p>

scholarly journals Towards a regional ocean forecasting system for the IBI (Iberia-Biscay-Ireland area): developments and improvements within the ECOOP project framework

Ocean Science ◽  
2012 ◽  
Vol 8 (2) ◽  
pp. 143-159 ◽  
Author(s):  
S. Cailleau ◽  
J. Chanut ◽  
J.-M. Lellouche ◽  
B. Levier ◽  
C. Maraldi ◽  
...  
Keyword(s):  
General Circulation ◽  
Large Scale ◽  
Vertical Mixing ◽  
Circulation Model ◽  
Storm Surges ◽  
Ocean General Circulation Model ◽  
Tidal Mixing ◽  
Basin Scale ◽  
Forecasting System ◽  
Ocean Forecasting

Abstract. The regional ocean operational system remains a key element in downscaling from large scale (global or basin scale) systems to coastal ones. It enables the transition between systems in which the resolution and the resolved physics are quite different. Indeed, coastal applications need a system to predict local high frequency events (inferior to the day) such as storm surges, while deep sea applications need a system to predict large scale lower frequency ocean features. In the framework of the ECOOP project, a regional system for the Iberia-Biscay-Ireland area has been upgraded from an existing V0 version to a V2. This paper focuses on the improvements from the V1 system, for which the physics are close to a large scale basin system, to the V2 for which the physics are more adapted to shelf and coastal issues. Strong developments such as higher regional physics resolution in the NEMO Ocean General Circulation Model for tides, non linear free surface and adapted vertical mixing schemes among others have been implemented in the V2 version. Thus, regional thermal fronts due to tidal mixing now appear in the latest version solution and are quite well positioned. Moreover, simulation of the stratification in shelf areas is also improved in the V2.

scholarly journals Can Lagrangian Tracking Simulate Tracer Spreading in a High-Resolution Ocean General Circulation Model?

2019 ◽  
Vol 49 (5) ◽  
pp. 1141-1157 ◽  
Author(s):  
Patrick Wagner ◽  
Siren Rühs ◽  
Franziska U. Schwarzkopf ◽  
Inga Monika Koszalka ◽  
Arne Biastoch
Keyword(s):  
General Circulation ◽  
Large Scale ◽  
Circulation Model ◽  
Eddy Diffusivity ◽  
Ocean General Circulation Model ◽  
Horizontal Resolution ◽  
Ocean Model ◽  
Time Step ◽  
Lagrangian Particles ◽  
Cape Basin

AbstractTo model tracer spreading in the ocean, Lagrangian simulations in an offline framework are a practical and efficient alternative to solving the advective–diffusive tracer equations online. Differences in both approaches raise the question of whether both methods are comparable. Lagrangian simulations usually use model output averaged in time, and trajectories are not subject to parameterized subgrid diffusion, which is included in the advection–diffusion equations of ocean models. Previous studies focused on diffusivity estimates in idealized models but could show that both methods yield similar results as long as the deformations-scale dynamics are resolved and a sufficient amount of Lagrangian particles is used. This study compares spreading of an Eulerian tracer simulated online and a cloud of Lagrangian particles simulated offline with velocities from the same ocean model. We use a global, eddy-resolving ocean model featuring 1/20° horizontal resolution in the Agulhas region around South Africa. Tracer and particles were released at one time step in the Cape Basin and below the mixed layer and integrated for 3 years. Large-scale diagnostics, like mean pathways of floats and tracer, are almost identical and 1D horizontal distributions show no significant differences. Differences in vertical distributions, seen in a reduced vertical spreading and downward displacement of particles, are due to the combined effect of unresolved subdaily variability of the vertical velocities and the spatial variation of vertical diffusivity. This, in turn, has a small impact on the horizontal spreading behavior. The estimates of eddy diffusivity from particles and tracer yield comparable results of about 4000 m2 s−1 in the Cape Basin.

scholarly journals The GPU version of LASG/IAP Climate System Ocean Model version 3 (LICOM3) under the heterogeneous-compute interface for portability (HIP) framework and its large-scale application

2021 ◽  
Vol 14 (5) ◽  
pp. 2781-2799
Author(s):  
Pengfei Wang ◽  
Jinrong Jiang ◽  
Pengfei Lin ◽  
Mengrong Ding ◽  
Junlin Wei ◽  
...  
Keyword(s):  
General Circulation ◽  
Large Scale ◽  
Vertical Direction ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Ocean Model ◽  
Climate System ◽  
Global Ocean ◽  
Processing Unit ◽  
Model Version

Abstract. A high-resolution (1/20∘) global ocean general circulation model with graphics processing unit (GPU) code implementations is developed based on the LASG/IAP Climate System Ocean Model version 3 (LICOM3) under a heterogeneous-compute interface for portability (HIP) framework. The dynamic core and physics package of LICOM3 are both ported to the GPU, and three-dimensional parallelization (also partitioned in the vertical direction) is applied. The HIP version of LICOM3 (LICOM3-HIP) is 42 times faster than the same number of CPU cores when 384 AMD GPUs and CPU cores are used. LICOM3-HIP has excellent scalability; it can still obtain a speedup of more than 4 on 9216 GPUs compared to 384 GPUs. In this phase, we successfully performed a test of 1/20∘ LICOM3-HIP using 6550 nodes and 26 200 GPUs, and on a large scale, the model's speed was increased to approximately 2.72 simulated years per day (SYPD). By putting almost all the computation processes inside GPUs, the time cost of data transfer between CPUs and GPUs was reduced, resulting in high performance. Simultaneously, a 14-year spin-up integration following phase 2 of the Ocean Model Intercomparison Project (OMIP-2) protocol of surface forcing was performed, and preliminary results were evaluated. We found that the model results had little difference from the CPU version. Further comparison with observations and lower-resolution LICOM3 results suggests that the 1/20∘ LICOM3-HIP can reproduce the observations and produce many smaller-scale activities, such as submesoscale eddies and frontal-scale structures.

Modulation of Westerly Wind Bursts by Sea Surface Temperature: A Semistochastic Feedback for ENSO

2007 ◽  
Vol 64 (9) ◽  
pp. 3281-3295 ◽  
Author(s):  
Geoffrey Gebbie ◽  
Ian Eisenman ◽  
Andrew Wittenberg ◽  
Eli Tziperman
Keyword(s):  
General Circulation ◽  
Large Scale ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Warm Pool ◽  
Detailed Knowledge ◽  
Westerly Wind ◽  
Stochastic Representation ◽  
Wind Bursts ◽  
Westerly Wind Bursts

Abstract Westerly wind bursts (WWBs) in the equatorial Pacific are known to play a significant role in the development of El Niño events. They have typically been treated as a purely stochastic external forcing of ENSO. Recent observations, however, show that WWB characteristics depend upon the large-scale SST field. The consequences of such a WWB modulation by SST are examined using an ocean general circulation model coupled to a statistical atmosphere model (i.e., a hybrid coupled model). An explicit WWB component is added to the model with guidance from a 23-yr observational record. The WWB parameterization scheme is constructed such that the likelihood of WWB occurrence increases as the western Pacific warm pool extends: a “semistochastic” formulation, which has both deterministic and stochastic elements. The location of the WWBs is parameterized to migrate with the edge of the warm pool. It is found that modulation of WWBs by SST strongly affects the characteristics of ENSO. In particular, coupled feedbacks between SST and WWBs may be sufficient to transfer the system from a damped regime to one with self-sustained oscillations. Modulated WWBs also play a role in the irregular timing of warm episodes and the asymmetry in the size of warm and cold events in this ENSO model. Parameterizing the modulation of WWBs by an increase of the linear air–sea coupling coefficient seems to miss important dynamical processes, and a purely stochastic representation of WWBs elicits only a weak ocean response. Based upon this evidence, it is proposed that WWBs may need to be treated as an internal part of the coupled ENSO system, and that the detailed knowledge of wind burst dynamics may be necessary to explain the characteristics of ENSO.

scholarly journals A Short Note on Marine Reservoir Age Simulations Used in IntCal20

Radiocarbon ◽  
2020 ◽  
Vol 62 (4) ◽  
pp. 865-871 ◽  
Author(s):  
Martin Butzin ◽  
Timothy J Heaton ◽  
Peter Köhler ◽  
Gerrit Lohmann
Keyword(s):  
General Circulation ◽  
Short Note ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Continental Margins ◽  
Planktic Foraminifera ◽  
Marginal Seas ◽  
Combining Data ◽  
Resolution Model ◽  
Reservoir Age

ABSTRACTBeyond ~13.9 cal kBP, the IntCal20 radiocarbon (14C) calibration curve is based upon combining data across a range of different archives including corals and planktic foraminifera. In order to reliably incorporate such marine data into an atmospheric curve, we need to resolve these records into their constituent atmospheric signal and marine reservoir age. We present results of marine reservoir age simulations enabling this resolution, applying the LSG ocean general circulation model forced with various climatic background conditions and with atmospheric radiocarbon changes according to the Hulu Cave speleothem record. Simulating the spatiotemporal evolution of reservoir ages between 54,000 and 10,700 cal BP, we find reservoir ages between 500 and 1400 yr in the low- and mid-latitudes, but also more than 3000 yr in the polar seas. Our results are broadly in agreement with available marine radiocarbon reconstructions, with the caveat that continental margins, marginal seas, or tropical lagoons are not properly resolved in our coarse-resolution model.

scholarly journals Enhancing Dynamical Seasonal Predictions through Objective Regionalization

2017 ◽  
Vol 56 (5) ◽  
pp. 1431-1442 ◽  
Author(s):  
Saleh Satti ◽  
Benjamin F. Zaitchik ◽  
Hamada S. Badr ◽  
Tsegaye Tadesse
Keyword(s):  
East Africa ◽  
General Circulation ◽  
Large Scale ◽  
Rainfall Variability ◽  
Circulation Model ◽  
Grid Cell ◽  
Ocean General Circulation Model ◽  
Seasonal Forecasts ◽  
Interannual Rainfall Variability ◽  
Local Grid

AbstractImproving seasonal forecasts in East Africa has great implications for food security and water resources planning in the region. Dynamically based seasonal forecast systems have much to contribute to this effort, as they have demonstrated ability to represent and, to some extent, predict large-scale atmospheric dynamics that drive interannual rainfall variability in East Africa. However, these global models often exhibit spatial biases in their placement of rainfall and rainfall anomalies within the region, which limits their direct applicability to forecast-based decision-making. This paper introduces a method that uses objective climate regionalization to improve the utility of dynamically based forecast-system predictions for East Africa. By breaking up the study area into regions that are homogenous in interannual precipitation variability, it is shown that models sometimes capture drivers of variability but misplace precipitation anomalies. These errors are evident in the pattern of homogenous regions in forecast systems relative to observation, indicating that forecasts can more meaningfully be applied at the scale of the analogous homogeneous climate region than as a direct forecast of the local grid cell. This regionalization approach was tested during the July–September (JAS) rain months, and results show an improvement in the predictions from version 4.5 of the Max Plank Institute for Meteorology’s atmosphere–ocean general circulation model (ECHAM4.5) for applicable areas of East Africa for the two test cases presented.

scholarly journals Comparison of ocean heat content from two eddy-resolving hindcast simulations with OFES1 and OFES2

2021 ◽  
Author(s):  
Fanglou Liao ◽  
Xiao Hua Wang ◽  
Zhiqiang Liu
Keyword(s):  
Heat Transport ◽  
General Circulation ◽  
Large Scale ◽  
Potential Temperature ◽  
Heat Content ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Ocean Heat Content ◽  
Global Ocean ◽  
Spatial Distributions

Abstract. The ocean heat content (OHC) estimates from high-resolution hindcast simulations from the Ocean General Circulation Model for the Earth Simulator Version 1 (OFES1) and Version 2 (OFES2), and a global objective analysis of subsurface temperature observations (EN4.2.1) were compared. There was an OHC increase in most of the global ocean over a 57-year period, mainly a result of vertical displacements of neutral density surfaces. However, we found substantial differences in the temporal and meridional distributions of the OHC between the two OFES hindcasts. The spatial distributions of potential-temperature change also differed significantly, especially in the Atlantic Ocean. The spatial distributions of the time-averaged surface heat flux and heat transport from the OFES1 and OFES2 were highly correlated, but differences could be seen. However, these differences, more specifically in the heat transport, were only partially responsible for the OHC differences. The marked OHC differences may arise from the different vertical mixing schemes and may impact the large-scale pressure field, and thus the geostrophic current. The work here should be a useful reference for future OFES users.

scholarly journals Evaluation of PMIP2 and PMIP3 simulations of mid-Holocene climate in the Indo-Pacific, Australasian and Southern Ocean regions

2017 ◽  
Vol 13 (11) ◽  
pp. 1661-1684 ◽  
Author(s):  
Duncan Ackerley ◽  
Jessica Reeves ◽  
Cameron Barr ◽  
Helen Bostock ◽  
Kathryn Fitzsimmons ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
General Circulation ◽  
Ice Core ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Warm Pool ◽  
Primary Objective ◽  
Convective Precipitation ◽  
Proxy Records ◽  
Proxy Reconstructions

Abstract. This study uses the simplified patterns of temperature and effective precipitation approach from the Australian component of the international palaeoclimate synthesis effort (INTegration of Ice core, MArine and TErrestrial records – OZ-INTIMATE) to compare atmosphere–ocean general circulation model (AOGCM) simulations and proxy reconstructions. The approach is used in order to identify important properties (e.g. circulation and precipitation) of past climatic states from the models and proxies, which is a primary objective of the Southern Hemisphere Assessment of PalaeoEnvironment (SHAPE) initiative. The AOGCM data are taken from the Paleoclimate Modelling Intercomparison Project (PMIP) mid-Holocene (ca. 6000 years before present, 6 ka) and pre-industrial control (ca. 1750 CE, 0 ka) experiments. The synthesis presented here shows that the models and proxies agree on the differences in climate state for 6 ka relative to 0 ka, when they are insolation driven. The largest uncertainty between the models and the proxies occurs over the Indo-Pacific Warm Pool (IPWP). The analysis shows that the lower temperatures in the Pacific at around 6 ka in the models may be the result of an enhancement of an existing systematic error. It is therefore difficult to decipher which one of the proxies and/or the models is correct. This study also shows that a reduction in the Equator-to-pole temperature difference in the Southern Hemisphere causes the mid-latitude westerly wind strength to reduce in the models; however, the simulated rainfall actually increases over the southern temperate zone of Australia as a result of higher convective precipitation. Such a mechanism (increased convection) may be useful for resolving disparities between different regional proxy records and model simulations. Finally, after assessing the available datasets (model and proxy), opportunities for better model–proxy integrated research are discussed.

scholarly journals The GPU version of LICOM3 under HIP framework and its large-scale application

2020 ◽  
Author(s):  
Pengfei Wang ◽  
Jinrong Jiang ◽  
Pengfei Lin ◽  
Mengrong Ding ◽  
Junlin Wei ◽  
...  
Keyword(s):  
Graphics Processing Units ◽  
General Circulation ◽  
High Performance ◽  
Large Scale ◽  
Data Transfer ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Ocean Model ◽  
Global Ocean ◽  
Almost All

Abstract. A high-resolution (1/20°) global ocean general circulation model with Graphics processing units (GPUs) code implementations is developed based on the LASG/IAP Climate system Ocean Model version 3 (LICOM3) under Heterogeneous-compute Interface for Portability (HIP) framework. The dynamic core and physics package of LICOM3 are both ported to the GPU, and 3-dimensional parallelization is applied. The HIP version of the LICOM3 (LICOM3-HIP) is 42 times faster than what the same number of CPU cores dose, when 384 AMD GPUs and CPU cores are used. The LICOM3-HIP has excellent scalability; it can still obtain speedup of more than four on 9216 GPUs comparing to 384 GPUs. In this phase, we successfully performed a test of 1/20° LICOM3-HIP using 6550 nodes and 26200 GPUs, and at the grand scale, the model’s time to solution can still obtain an increasing, about 2.72 simulated years per day (SYPD). The high performance was due to putting almost all of computation processes inside GPUs, and thus greatly reduces the time cost of data transfer between CPUs and GPUs. At the same time, a 14-year spin-up integration following the phase 2 of Ocean Model Intercomparison Project (OMIP-2) protocol of surface forcing has been conducted, and the preliminary results have been evaluated. We found that the model results have little differences from the CPU version. Further comparison with observations and lower-resolution LICOM3 results suggests that the 1/20° LICOM3-HIP can not only reproduce the observations, but also produce much smaller scale activities, such as submesoscale eddies and frontal scales structures.

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