A report from JCAR to inform the ICARP IV Process
Topic Area 2: Observing, Reconstructing, and Predicting Future Climate
Dynamics and Ecosystem Responses
27 February 2024
Prepared by Shigeto Nishino1), Teruo Aoki2), Yuri Fukai1), Tsubasa Kodaira3), Masahiro Minowa4),
Daiki Nomura5),6),7), Kazutoshi Sato2), Tetsuo Sueyoshi1), Nozomu Takeuchi8), Yutaka Tobo2), andMasakazu Yoshimori9)
1) Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan
2) National Institute of Polar Research, Tachikawa, Japan
3) Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Japan
4) Institute of Low Temperature Science, Hokkaido University, Sapporo, Japan
5) Field Science Center for Northern Biosphere, Hokkaido University, Hakodate, Japan
6) Faculty/Graduate School of Fisheries Sciences, Hokkaido University, Hakodate, Japan
7) Arctic Research Center, Hokkaido University, Sapporp, Japan
8) Graduate School of Science, Chiba University, Chiba, Japan
9) Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Japan

Japan Consortium for Arctic Environmental Research (JCAR) published “Long-term Plan for Arctic
Environmental Research (JCAR, 2024a)” with its Executive Summary (JCAR, 2024b) that includes
research priorities from the viewpoints of Japanese Arctic research communities. Herein, we discuss
topics related to the observation, reconstruction, and prediction of future climate dynamics andecosystem responses based on the Executive Summary (JCAR, 2024b), towards which the Japanese
research communities can implement priority studies in the next decade.
The main areas of research in the atmospheric sciences include understanding of processes
connecting different time scales from weather to climate, interactions among the elements of the Arcticand those from outside the Arctic, and coupling between the troposphere and stratosphere and can bestudied through integrating observations, modeling, and data assimilation. The climate system has ahierarchical structure comprising complex, interconnected processes at various spatiotemporal scales.
Thus, a climate prediction is required to incorporate all relevant processes. Otherwise, numericalmodels for climate predictions must be strategically selected for various applications. For short-term
future forecasts, the initialization technique is vital and requires the establishment of an appropriate

1assimilation method. For long-term future projections, reproducing current climate states is also
important. Because air–ice–sea coupled systems must be satisfactorily represented in models, the seaice thickness should be continuously monitored to assimilate as a crucial dataset. As the climate varies
internally and in response to external forcing, studies on the mechanisms of internal climate variability,
forced response, and modulation of internal variability with changes in the mean climate state with afocus on Arctic regions are needed for predicting the future climate dynamics better.
Many aspects of the climate interaction between the Arctic and extra-Arctic (e.g., sub-Arctic andmid-latitude) regions remain unknown. Scientifically understanding such teleconnections is one of theessential factors for understanding current climate variability and predicting its future; additionally,
this is further important in investigating the cause of extreme events in and out of the Arctic regionand obtaining their future perspective. Research priorities on climate teleconnection are to understandits mechanism between the Arctic and extra-Arctic regions, sustaining mechanisms for modes ofnatural climate variability and their modulations under global warming, and identifying the link
between specific extreme events and global-scale climate teleconnections.
Furthermore, clouds and their physical processes, greenhouse gases, and aerosols are importantresearch topics. Recently, Japan launched a second-generation global imager (SGLI), which enables
the observation of atmospheric parameters related to clouds and aerosols as well as geophysicalparameters on the ground surface (snow and ice, vegetation, and ocean areas). Moreover, to promote
the future Arctic research, it is highly desirable to introduce dedicated aircraft for earth observations
and establish a system to operate aircrafts. In the past few years, most research on the middle andupper atmosphere and geospace has been led by Japanese researchers as part of an international joint
research project, along with starting new satellite observations ("Arase": Exploration of energization
and Radiation in Geospace) and large radar observations (EISCAT_3D radar). It is important toestablish a global radar network that includes Japan’s large atmospheric radar plus the EISCAT_3D
radar, which will provide an extremely strong research base for global atmospheric environment
research.
As for ocean sciences, Arctic Atlantification and Pacification are emerging topics that characterize
Arctic environmental and ecosystem changes not only in the Atlantic and Pacific gateway regions but
also in the central Arctic Ocean. International collaborations are necessary to conduct large-scaleocean observations that connect the Atlantic and Pacific gateways with central Arctic, such as theSynoptic Arctic Survey (SAS), and to obtain baseline data on a decadal timescale. Interannual
monitoring of marine environmental and ecosystem changes in priority areas, such as biologicalhotspots interspersed throughout the pan-Arctic, also require internationally coordinated observations

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using multiple vessels at different times of the year, such as the Pacific-, Atlantic-, and Siberian-Arctic
Distributed Biological Observatories (DBOs). At present, Japan is building a new icebreaker capableof transecting the Arctic ice zones, which will largely contribute to the pan-Arctic international
collaborative studies (SAS and DBOs). Furthermore, the icebreaker is to be equipped with a fishfinding echo sounder with advanced onboard instruments capable of withstanding extreme lowtemperature conditions; thus, it will contribute to scientific surveys related to the central Arctic Ocean
fisheries agreement. To advance Japanese Arctic research in the future, it is necessary to establish asystem that can deploy in situ observations (including on ice), manned observation stations, andunmanned observations (AUVs, drones, etc.) using the icebreaker as a platform and to expand
observations across the Arctic Ocean by including organized collaboration with other countries.
To understand changes in the Arctic land surface, continuing the long-term observations ofterrestrial ecosystems and permafrost in Russia and Alaska by Japanese scientists with international
collaborations is necessary. International programs, such as Terrestrial Multidisciplinary distributed
Observatories for the Study of Arctic Connections (T-MOSAiC), are essential to connect observations
on continents in concentric circles in the longitude direction, and sustainable north-south transects inthe latitude direction are also needed. Further development and improvement of polar observation
systems are required to complement the information from remote sensing data. Further, it is necessary
to promote analysis of wide-area environmental changes through the use of data from multiple
satellites, including those equipped with optical and microwave sensors. Natural ecosystems andpermafrost processes are interconnected to events of various spatiotemporal scales; hence, they need
to be understood using land-surface and ecosystem models constructed at appropriate spatiotemporalscales. In addition, it is necessary to establish a database containing information from land area
research and combine it with social, cultural, and economic analyses. Occurrences of land disasters,such as Eurasian and North American wildfires, should be analyzed in depth by combining in situ andsatellite observations.
Snow and ice are key components of the Arctic environment. The PALSAR series of Japan, aleading L-band synthetic aperture radar, enables the observations of changes in snow and ice usingparameters such as flow rates in glaciers and ice sheets and land subsidence caused by permafrost
thawing. Observations of snow and ice using microwave radiometers began in the 1970s, and theAMSR series developed by Japan has been the leading satellite in the world for sea-ice observations
since 2002. The melting of snowpacks is primarily controlled by air temperature, solar radiation, andsurface albedo. Therefore, quantitative evaluations of surface albedo and its dependence on the snow
grain size and light-absorbing impurity concentration are issues for the future studies. To evaluate theimpact of impurities on melting, quantification of organic and inorganic materials in snow/ice and3their impact on surface albedo are crucial. Particularly in the field of glacial microbes, Japanese
researchers are assuming leading roles in the in situ observations and numerical modeling.
Mass loss in the Greenland ice sheets and Arctic glaciers is a dominant factor in the sea level risein the 21st century. Under the framework of Japanese Arctic research programs (GRENE, ArCS andArCS II), the long-term monitoring of climatic conditions and in situ studies on ice-sheet surface
processes have been performed in northwestern Greenland since 2012. The programs also perform
monitoring of glacier mass balance and studies on glacier–ocean interactions in the same area incollaboration with local communities in the Qaanaaq region as well as with international researchers.
To accurately understand the mass loss in snow and ice in the Arctic and its global and social
consequences, it is important to strengthen the synergy among long-term field observations, satellite
remote sensing, and numerical modeling. The efforts for investigating Greenland ice sheets andglaciers using in situ and satellite observations should be applied to sea-ice studies. Sea ice is one ofthe principal factors that characterize the Arctic climate. Additionally, it is important for the ecosystemand existence of living organisms in the Arctic region and directly impacts human activities, such as
ship navigation and fishery. Therefore, sea-ice prediction studies have gained special interest among
the various aspects of the Arctic climate research. Knowledge of physical processes, such as waves,snow on sea ice, representation of leads and polynyas and fluxes from there is vital for efficient seaice predictions. Feedback between physical and ecosystem processes associated with sea ice could be
essential for earth system modeling.
The improved reconstruction of the Northern Hemisphere ice-sheet evolution and reconstruction of
the past sea-ice distribution is important to understand the Arctic climate system. Because the Arcticregion (land and sea) is rapidly changing, paleoenvironmental analyses with high temporal resolution
focused on the near past are greatly needed. Furthermore, it is necessary to plan sampling in theestuaries of large rivers where high sedimentation rates can be expected. Ice core studies have been
conducted in the last four decades using several ice cores drilled from the Greenland ice sheet andother Arctic glaciers to reconstruct past climate and atmospheric conditions. Future ice core studies
need to propose new processes and mechanisms using new analytical techniques and numericalsimulations of Earth’s environmental systems and/or to contribute to certain geo-engineering studies.
To elucidate polar amplification mechanisms throughout the Earth’s history from the process level toclimate system point of view, continuous supporting of the international activities of model–modeland model–data comparisons is needed.
Japanese researchers can also play a leading role in strategically promoting solid Earth science
research in the Artic in this decade. In addition, since the themes listed below can be expected to make4

a significant contribution from the Japanese research community, the research system for these issues
should be established over the next decade.
- Geology: From the early Earth and early life to the Paleozoic Caledonian orogeny, as well asbasement rock specimens collected from beneath the Greenland ice sheet will be the main focus asJapan’s strengths in geochronology and isotope geochemistry.
- Marine geophysics: Understanding Cretaceous igneous activity, continental breakup, and seafloor
spreading processes is important. Observation programs based on new research vessels in the Arcticand the active use of underwater robot technologies for unmanned exploration and rock sampling areindispensable for understanding the abovementioned topics.
- Geodesy: Monitoring ice-sheet mass balance in global warming urgently requires satellite-based
analysis of regional crustal deformation and development of an absolute gravimeter network and highresolution numerical modeling to reconstruct these observables.
Submitted together with
JCAR (2024b): Executive Summary of Long-term Plan for Arctic Environmental Research.
References:
Japan Consortium for Arctic Environmental Research (2024a). Long-term Plan for Arctic
Environmental Research. [in Japanese]
Japan Consortium for Arctic Environmental Research (2024b). Executive Summary of Long-term
Plan for Arctic Environmental Research. https://www.jcar.org/e/longterm/5