東京大学 · 地球惑星科学
アレクサンドル・コーキョン教授の研究室では、水素・酸素の安定同位体を用いた気候モデルの開発と応用を柱として、地球システムモデルにおける水循環の精密な再現を目指しています。特に、氷核や大気中の同位体比を用いた古気候再構築や、過去の気候変動（例：中ホロセン）のメカニズム解明が主な研究テーマです。同位体トレーサーを統合した大気・海洋・陸面モデルの開発を通じて、気候変動のメカニズム解明と古気候データとの直接比較を推進しています。
Figures are computed from collected data and may differ slightly.
Abstract. We present here the first results, for the preindustrial and mid-Holocene climatological periods, of the newly developed isotope-enhanced version of the fully coupled Earth system model MPI-ESM, called hereafter MPI-ESM-wiso. The water stable isotopes H216O, H218O and HDO have been implemented into all components of the coupled model setup. The mid-Holocene provides the opportunity to evaluate the model response to changes in the seasonal and latitudinal distribution of insolation indu
Abstract We present here results of new isotope‐enabled simulations with an enhanced ECHAM6‐wiso model version nudged to the ERA5 reanalyses, at two different spatial resolutions, for the period 1979–2018. The isotopic content of snow on sea ice is considered, yielding surface water vapor with lower isotope ratios over sea ice covered areas, and the kinetic fractionation factors for oceanic evaporation are assumed as independent of wind speed. Also, the supersaturation equation was slightly re‐t
Context. Abreu et al. (2012, A&A. 548, A88) have recently compared the periodicities in a 14C – 10Be proxy record of solar variability during the Holocene and found a strong similarity with the periodicities predicted on the basis of a model of the time-dependent torque exerted by the planets on the sun’s tachocline. If verified, this effect would represent a dramatic advance not only in the basic understanding of the Sun’s variable activity, but also in the potential influence of this variabili
Abstract. Ice cores are exceptional archives which allow us to reconstruct a wealth of climatic parameters as well as past atmospheric composition over the last 800 kyr in Antarctica. Inferring the variations in past accumulation rate in polar regions is essential both for documenting past climate and for ice core chronology. On the East Antarctic Plateau, the accumulation rate is so small that annual layers cannot be identified and accumulation rate is mainly deduced from the water isotopic com
Abstract Improving the representation of the hydrological cycle in atmospheric general circulation models (AGCMs) is one of the main challenges in modeling the Earth's climate system. One way to evaluate model performance is to simulate the transport of water isotopes. Among those available, tritium is an extremely valuable tracer, because its content in the different reservoirs involved in the water cycle (stratosphere, troposphere, and ocean) varies by order of magnitude. Previous work incorpo
Abstract. Numerical simulations employing prognostic stable water isotopes can not only facilitate our understanding of hydrological processes and climate change but also allow for a direct comparison between isotope signals obtained from models and various archives. In the current work, we describe the performance and explore the potential of a new version of the Earth system model AWI-ESM (Alfred Wegener Institute Earth System Model), labeled AWI-ESM-2.1-wiso, in which we incorporated three is
Abstract. A ten-year record of oxygen and hydrogen isotopic composition of precipitation is here presented: from 2008 to 2017, 1483 daily precipitation samples were collected all-year round on a raised platform at Concordia Station, East Antarctica. Weather data were retrieved from the Italian Antarctic Meteo-Climatological Observatory AWS, while ERA5 was used to estimate total precipitation. The δ-temperature relationships were moderately high for daily data (r2=0.63 and 0.64 for δ18O and δ2H,
We present here the first results, for the preindustrial and mid-Holocene climatological periods, of the newly developed isotope-enhanced version of the fully coupled Earth system model MPI-ESM, called hereafter MPI-ESM-wiso. The water stable isotopes H216O, H218O and HDO have been implemented into all components of the coupled model setup. The mid-Holocene provides the opportunity to evaluate the model response to changes in the seasonal and latitudinal distribution of insolation induced by dif
Abstract. We present here the first results, for the pre-industrial and mid-Holocene climatological periods, of the newly developed isotope-enhanced version of the fully coupled Earth system model MPI-ESM, called hereafter MPI-ESM-wiso. The water stable isotopes H216O, H218O and HDO have been implemented into all components of the coupled model setup: the atmosphere model ECHAM6, the land/soil vegetation model JSBACH, and the ocean/sea ice model MPIOM. The exchanges of the related isotope masses
The Laschamp excursion is a period of reduced geomagnetic field intensity occurring 40.7 ± 1.0 kyr ago. As a consequence, cosmogenic isotope production increased dramatically and its sensitivity to solar activity was enhanced during this period. The latter occurs because a larger fraction of the lower-energy interstellar galactic cosmic-ray particles, normally excluded by the geomagnetic field, is able to reach Earth's atmosphere. This produces a cosmogenic isotope production signal with a signi
Abstract. In order to investigate the impact of spatial resolution on the discrepancy between simulated δ18O and observed δ18O in Greenland ice cores, regional climate simulations are performed with the isotope-enabled regional climate model (RCM) COSMO_iso. For this purpose, isotope-enabled general circulation model (GCM) simulations with the ECHAM5-wiso general circulation model (GCM) under present-day conditions and the MPI-ESM-wiso GCM under mid-Holocene conditions are dynamically downscaled
The polar ice cores, in addition to improving our understanding of the climate, give access to beryllium-10 (10Be) fallout, an isotope of cosmogenic origin created by the interaction of Galactic Cosmic Rays with the upper atmosphere. Its production rate depends on the intensity of the primary cosmic rays, which are modulated by solar activity and the Earth's magnetic field. 10Be therefore provides information on these two parameters. It has allowed, among others, the improvement of ice cores chr
Abstract Modeling tritium content in water presents a meaningful way to evaluate the representation of the water cycle in climate models as it traces fluxes within and between the reservoirs involved in the water cycle (stratosphere, troposphere, and ocean). In this study, we present the implementation of natural tritium in water in the atmospheric general circulation model (AGCM) MIROC5‐iso and its simulation for the period 1979–2018. Owing to recently published tritium production calculations,
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