No abstract

Sustained ocean observations are crucial to understand both natural processes occurring in the ocean and human influence on the marine ecosystems. The information they provide increases our understanding and is therefore beneficial to the society as a whole because it contributes to a more efficient use and protection of the marine environment, upon which human livelihood depends. In addition the oceans, which occupy 73% of the planet surface and host 93% of the biosphere, play a massive role in controlling the climate. Eulerian or fixed-point observatories are an essential component of the global ocean observing system as they provide several unique features that cannot be found in other systems and are therefore complementary to them. In addition they provide a unique opportunity for multidisciplinary and interdisciplinary work, combining physical, chemical and biological observations on several time scales. The fixed-point open ocean observatory network (FixO3) integrates the 23 European open ocean fixed-point observatories in the Atlantic Ocean and in the Mediterranean Sea. The program also seeks to improve access to key installations and the knowledge they provide for the wider community, from scientists, to businesses, to civil society. This paper summarises the rationale behind open ocean observatories monitoring the essential ocean variables. It also provides an estimate of the costs to operate a typical fixed-point observatory such as those included in the FixO3 network. Finally an assessment of the type of data and services provided by ocean observations and their value to society is also given.

Abstract. Earth system and climate modelling involves the simulation of processes on a wide range of scales and within and across various compartments of the Earth system. In practice, component models are often developed independently by different research groups, adapted by others to their special interests and then combined using a dedicated coupling software. This procedure not only leads to a strongly growing number of available versions of model components and coupled setups but also to model- and high-performance computing (HPC)-system-dependent ways of obtaining, configuring, building and operating them. Therefore, implementing these Earth system models (ESMs) can be challenging and extremely time consuming, especially for less experienced modellers or scientists aiming to use different ESMs as in the case of intercomparison projects. To assist researchers and modellers by reducing avoidable complexity, we developed the ESM-Tools software, which provides a standard way for downloading, configuring, compiling, running and monitoring different models on a variety of HPC systems. It should be noted that ESM-Tools is not a coupling software itself but a workflow and infrastructure management tool to provide access to increase usability of already existing components and coupled setups. As coupled ESMs are technically the more challenging tasks, we will focus on coupled setups, always implying that stand-alone models can benefit in the same way. With ESM-Tools, the user is only required to provide a short script consisting of only the experiment-specific definitions, while the software executes all the phases of a simulation in the correct order. The software, which is well documented and easy to install and use, currently supports four ocean models, three atmosphere models, two biogeochemistry models, an ice sheet model, an isostatic adjustment model, a hydrology model and a land-surface model. Compared to previous versions, ESM-Tools has lately been entirely recoded in a high-level programming language (Python) and provides researchers with an even more user-friendly interface for Earth system modelling. ESM-Tools was developed within the framework of the Advanced Earth System Model Capacity project, supported by the Helmholtz Association.

<p>Earth system and climate modelling involves the simulation of processes on a large range of scales, and within very different components of the earth system. In practice, component models from different institutes are mostly developed independently, and then combined using a dedicated coupling software.</p><p>This procedure not only leads to a wildly growing number of available versions of model components as well as coupled setups, but also to a specific way of obtaining and operating many of these. This can be a challenging problem (and potentially a huge waste of time) especially for unexperienced researchers, or scientists aiming to change to a different model system, e.g. for intercomparisons.</p><p>In order to define a standard way of downloading, configuring, compiling and running modular ESMs on a variety of HPC systems, AWI and partner institutions develop and maintain the OpenSource ESM-Tools software (https://www.esm-tools.net). Our aim is to provide standard solutions to typical problems occurring within the workflow of model simulations such as calendar operations, data postprocessing and monitoring, sanity checks, sorting and archiving of output, and script-based coupling (e.g. ice sheet models, isostatic adjustment models). The user only provides a short (30-40 lines) runscript of absolutely necessary experiment specific definitions, while the ESM-Tools execute the phases of a simulation in the correct order. A user-friendly API ensures that more experienced users have full control over each of these phases, and can easily add functionality. A GUI has been developed to provide a more intuitive approach to the modular system, and also to add a graphical overview over the available models and combinations.</p><p>Since revision 2 (released on March 19<sup>th</sup> 2019), the ESM-Tools were entirely re-written, separating the implementation of actions (written in Python 3) from any information that we have, either on models, coupled setups, software tools, HPC systems etc. into nicely structured yaml configuration files. This has been done to reduce maintenance problems, and also to ensure that also unexperienced scientist can easily edit configurations, or even add new models or software without any programming experience. Since revision 3 the ESM-Tools support four ocean models (FESOM1, FESOM2, NEMO, MPIOM), three atmosphere models (ECHAM6, OpenIFS, ICON), two BGC models (HAMOCC, REcoM), an ice sheet (PISM) and an isostatic adjustment model (VILMA) as well as standard settings for five HPC systems. For the future we plan to add interfaces to regional models and soil/hydrology models.</p><p>The Tools currently have more than 70 registered users from 5 institutions, and more than 40 authors of contributions to either model configurations or functionality.</p>