The current explosion in machine learning for climate has led to skilled, computationally cheap emulators for the atmosphere. However, the research for ocean emulators remains nascent despite the large potential for accelerating coupled climate simulations and improving ocean forecasts on all timescales. There are several fundamental questions to address that can facilitate the creation of ocean emulators. Here we focus on two questions: 1) the role of the atmosphere in improving the extended skill of the emulator and 2) the representation of variables with distinct timescales (e.g., velocity and temperature) in the design of any emulator. In tackling these questions, we show stable prediction of surface fields for over 8 years, training and testing on data from a high-resolution coupled climate model, using results from four regions of the globe. Our work lays out a set of physically motivated guidelines for building ocean climate emulators.
HClimRep-Ocean: A Global Ocean Emulator on an Unstructured Mesh
Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research（阿尔弗雷德·魏格纳亥姆霍兹极地与海洋研究中心）；Forschungszentrum Jülich GmbH（于利希研究中心）；Karlsruhe Institute of Technology（卡尔斯鲁厄理工学院）；European Center for Medium-Range Weather Forecasts（欧洲中期天气预报中心）；University of Cologne（科隆大学）；University of Bremen（不来梅大学）
Modeling globally averaged information on climate forcing from the land surface temperature data, the sea surface temperatures (SST) and the empirically determined relationship between the changes in SST and the turbulent diffusion of heat into the upper ocean demonstrates a consistent link. The modeling is accurate throughout the 20th century despite the different phases of the Interdecadal Pacific Oscillation (IPO) or the strong divergence between land and ocean surface warming. It only fails during the last 15 years when SST drops well below the trend. The finding reinforces the view that s…
University of California, Irvine（加州大学欧文分校）；Columbia University（哥伦比亚大学）；Ludwig-Maximilian-University（路德维希-马克西米利安大学）
Artificial neural-networks have the potential to emulate cloud processes with higher accuracy than the semi-empirical emulators currently used in climate models. However, neural-network models do not intrinsically conserve energy and mass, which is an obstacle to using them for long-term climate predictions. Here, we propose two methods to enforce linear conservation laws in neural-network emulators of physical models: Constraining (1) the loss function or (2) the architecture of the network itself. Applied to the emulation of explicitly-resolved cloud processes in a prototype multi-scale clim…
A set of idealized experiments are performed to analyze the competing effects of declining atmospheric CO2 concentrations, the opening of an ocean gateway, and varying orbital parameters. These forcing mechanisms, which influence the global mean climate state, may have played a role for triggering climate transitions of the past (for example during the Eocene-Oligocene climate transition and the build-up of the Antarctic Ice Sheet). Sensitivity simulations with a coupled atmosphere-ocean general circulation model are conducted to test these three forcings and their roles for the global climate…
In this report we set forth a simulation method for long-term simulations of NorESM, the Norwegian Earth System Model. In this the sediment is repeatedly decoupled and coupled to the ocean model (BLOM/iHAMOCC), a process called burst coupling. Through this, the ocean (seawater and sediment) is brought into an approximate steady state. We show that just the model has to run at least 50000 yr to get in an approximate steady state. With burst coupling this can be done in a computationally reasonable time (wall time in the order of one week). The method can be used to generate the sediment over hu…
Samudra 2: Scaling Ocean Emulators across Resolutions
Courant Institute School of Mathematics, Computing, and Data Science, New York University（Courant学院数学、计算与数据科学系，纽约大学）；Open Athena AI Foundation, Inc.（开放Athena人工智能基金会）；Program in Atmospheric and Oceanic Sciences, Princeton University（大气与海洋科学项目，普林斯顿大学）
We use numerical climate simulations, paleoclimate data, and modern observations to study the effect of growing ice melt from Antarctica and Greenland. Meltwater tends to stabilize the ocean column, inducing amplifying feedbacks that increase subsurface ocean warming and ice shelf melting. Cold meltwater and induced dynamical effects cause ocean surface cooling in the Southern Ocean and North Atlantic, thus increasing Earth's energy imbalance and heat flux into most of the global ocean's surface. Southern Ocean surface cooling, while lower latitudes are warming, increases precipitation on the …
Department of Aeronautics and Astronautics, Massachusetts Institute of Technology（航空与航天系，麻省理工学院）；Center for Sustainability Science and Strategy, Massachusetts Institute of Technology（可持续科学与战略中心，麻省理工学院）；Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology（地球、大气与行星科学系，麻省理工学院）；Brahmal Vasudevan Institute for Sustainable Aviation, Department of Aeronautics, Imperial College London（可持续航空研究所，帝国理工学院伦敦校区）；Institute for Data, Systems, and Society, Massachusetts Institute of Technology（数据、系统与社会研究所，麻省理工学院）
Atmosphere and ocean are coupled via air-sea interactions. The atmospheric conditions fuel the ocean circulation and its variability, but the extent to which ocean processes can affect the atmosphere at decadal time scales remains unclear. In particular, such low-frequency variability is difficult to extract from the short observational record, meaning that climate models are the primary tools deployed to resolve this question. Here, we assess how the ocean's intrinsic variability leads to patterns of upper-ocean heat content that vary at decadal time scales. These patterns have the potential …
MERCURY: A fast and versatile multi-resolution based global emulator of compound climate hazards
University of Oxford（牛津大学）；Montreal Polytechnique（蒙特利尔理工学院）；Columbia Climate School（哥伦比亚气候学院）；International Institute for Applied Systems Analysis（国际应用系统分析研究所）；Universität Leipzig（莱比锡大学）；IRI THESys；Humboldt-Universität zu Berlin（柏林洪堡大学）；Institute Pierre-Simone-Laplace（皮埃尔-西蒙·拉普拉斯研究所）
Atmospheric transient eddies and low-frequency flow contribution to the ocean surface wave climate in the North Atlantic during boreal winter is investigated (1980 - 2016). We conduct a set of numerical simulations with a state-of-the-art spectral wave model Wavewatch III forced by decomposed wind fields derived from the ERA-Interim reanalysis (0.7° horizontal resolution). Synoptic-scale processes (2-10 day bandpassed winds) are found to have the largest impact on the formation of wind waves in the western mid-latitude North Atlantic along the North American and western Greenland coasts. The e…
Cloud microphysical parameterizations in atmospheric models describe the formation and evolution of clouds and precipitation, a central weather and climate process. Cloud-associated latent heating is a primary driver of large and small-scale circulations throughout the global atmosphere, and clouds have important interactions with atmospheric radiation. Clouds are ubiquitous, diverse, and can change rapidly. In this work, we build the first emulator of an entire cloud microphysical parameterization, including fast phase changes. The emulator performs well in offline and online (i.e. when coupl…
The influence of atmospheric composition on the climates of present-day and early Earth has been studied extensively, but the role of ocean composition has received less attention. We use the ROCKE-3D ocean-atmosphere general circulation model to investigate the response of Earth's present-day and Archean climate system to low vs. high ocean salinity. We find that saltier oceans yield warmer climates in large part due to changes in ocean dynamics. Increasing ocean salinity from 20 g/kg to 50 g/kg results in a 71% reduction in sea ice cover in our present-day Earth scenario. This same salinity …
Sensitivity of the ECMWF seasonal forecast model to CO2 and anthropogenic aerosol forcings: Experimental design and impact on climate trends
ECMWF（欧洲中期天气预报中心）；Department of Meteorology and Geophysics, University of Vienna（维也纳大学气象与地球物理系）；NCAS, University of Oxford, Atmospheric, Oceanic and Planetary Physics（牛津大学大气、海洋和行星物理国家环境科学研究中心）
Drought poses a significant threat to the delicate economies in subsaharan Africa. This study investigates the influence of large scale ocean oscillation on drought in West Africa. Standardized Precipitation Index for the region was computed using monthly precipitation data from the Climate Research Unit during the period 1961 -1990. The impact of three ocean oscillation indices - Southern Ocean Index (SOI), Pacific Decadal Oscillation (PDO) and North Atlantic Oscillation (NAO) on drought over West Africa was investigated using linear correlation, co-integration test, mutual information and no…
We developed an emulator for Integrated Assessment Models (emIAM) based on a marginal abatement cost (MAC) curve approach. Using the output of IAMs in the ENGAGE Scenario Explorer and the GET model, we derived a large set of MAC curves: ten IAMs; global and eleven regions; three gases CO2, CH4, and N2O; eight portfolios of available mitigation technologies; and two emission sources. We tested the performance of emIAM by coupling it with a simple climate model ACC2. We found that the optimizing climate-economy model emIAM-ACC2 adequately reproduced a majority of original IAM emission outcomes u…
LUCIE-3D: A three-dimensional climate emulator for forced responses
Pennsylvania State University（宾夕法尼亚州立大学）；Allen Insitute of Artificial Intelligence（人工智能 Allen 机构）；Argonne National Laboratory（阿贡国家实验室）；University of California, Santa Cruz（加州大学圣克鲁兹分校）
Freshwater forcing from a retreating Antarctic Ice Sheet could have a wide range of impacts on future global climate. Here, we report on multi-century (present-2250) climate simulations performed using a fully coupled numerical model integrated under future greenhouse gas emissions scenarios IPCC RCP4.5 and 8.5, with meltwater discharge provided by a dynamic-thermodynamic ice sheet model. Accounting for Antarctica's meltwater contribution raises sub-surface ocean temperatures by 1 C at the ice margin, beyond rates currently projected. In contrast, 2-10 C cooler surface air and ocean temperatur…
Impact of Data-Driven Eddy Parameterization on Climate State in an Idealized Coupled CESM Model
Courant Institute School of Mathematics, Computing, and Data Science, New York University（纽约大学柯朗数学科学研究所）；Atmospheric and Oceanic Sciences Program, Princeton University（普林斯顿大学大气与海洋科学项目）
The Biogeochemical-Argo (BGC-Argo) program is building a network of globally distributed, sensor-equipped robotic profiling floats, improving our understanding of the climate system and how it is changing. These floats, however, are limited in the number of variables measured. In this study, we train neural networks to predict silicate and phosphate values in the Southern Ocean from temperature, pressure, salinity, oxygen, nitrate, and location and apply these models to earth system model (ESM) and BGC-Argo data to expand the utility of this ocean observation network. We trained our neural net…
The climate impact of ocean gateway openings during the Eocene-Oligocene transition is still under debate. Previous model studies employed grid resolutions at which the impact of mesoscale eddies has to be parameterized. We present results of a state-of-the-art eddy-resolving global ocean model with a closed Drake Passage, and compare with results of the same model at non-eddying resolution. An analysis of the pathways of heat by decomposing the meridional heat transport into eddy, horizontal, and overturning circulation components indicates that the model behavior on the large scale is qualit…
Constructing efficient score functions for rare event simulation in high-dimensional ocean-climate models
Institute for Marine and Atmospheric research Utrecht, Department of Physics, Utrecht University（乌得勒支大学海洋与大气研究所物理系）；Utrecht University（乌得勒支大学）；Netherlands eScience Center（荷兰电子科学中心）；IMEC；Centre for Complex Systems Studies, Department of Physics, Utrecht University（乌得勒支大学复杂系统研究中心物理系）
Climate-Adaptive and Cascade-Constrained Machine Learning Prediction for Sea Surface Height under Greenhouse Warming
Tianjin University（天津大学）；The Hong Kong University of Science and Technology（香港科技大学）；Institute of Atmospheric Physics, Chinese Academy of Sciences（中国科学院大气物理研究所）；University of Chinese Academy of Sciences（中国科学院大学）
Various climate states at high obliquity are realized for a range of stellar irradiance using a dynamical atmosphere-ocean-sea ice climate model in an Aquaplanet configuration. Three stable climate states are obtained that differ in the extent of the sea ice cover. For low values of irradiance the model simulates a Cryoplanet that has a perennial global sea ice cover. By increasing stellar irradiance, transitions occur to an Uncapped Cryoplanet with a perennial equatorial sea ice belt, and eventually to an Aquaplanet with no ice. Using an emulator model we find that the Uncapped Cryoplanet is …
