A report from JCAR to inform the ICARP IV Process
Topic Area 1: The Role of the Arctic in the Global System
25 February 2024

Prepared by Masakazu Yoshimori1) and Daiki Nomura2), 3), 4)
1) Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Japan
Contact: masakazu@aori.u-tokyo.ac.jp
2) Field Science Center for Northern Biosphere, Hokkaido University, Hakodate, Japan
3) Faculty/Graduate School of Fisheries Sciences, Hokkaido University, Japan
4) Arctic Research Center, Hokkaido University, Japan
Japan Consortium for Arctic Environmental Research (JCAR) published “Long-term Plan for Arctic
Environmental Research (JCAR, 2024)” with its Executive Summary (JCAR, 2024) that includes
research priorities from the viewpoints of Japanese Arctic research communities. Here, from theExecutive Summary (JCAR, 2024), we have extracted, edited, and added elements that the Japanese
research community could contribute significantly to the implementation of priority studies for thenext decade related to “Topic Area 1: The Role of the Arctic in the Global System” of ICARP IV. We
note that some comments from JCAR members were reflected in the document.
•Global energy budget with some emphasis on the impact of terrestrial changesWhile the Arctic covers only a small portion of the Earth’s surface, it constitutes an important elementof the global environmental system that is highly interactive with the regions outside the Arctic.
Changes in surface albedo associated with snow, ice, and vegetation cover disturb the Earth’s energy
budget. To understand and accurately predict such changes, it is necessary to establish a continuous
and improved polar observation system whose target includes terrestrial ecosystems and permafrost.
The in-situ observations are vital for the effective use of satellite remote sensing data which enables
us to capture the Arctic-wide changes of the Earth’s surface.
Changing fluxes (emissions and sinks) of CO2 and CH4 at the surface need to be evaluated in bothobservational and modeling studies, making use of isotopic ratios of these compounds. Emissions of
CO2 and CH4 from organic matter in the permafrost can also disturb the global energy budget. As theprocesses in the natural ecosystem and permafrost occur on various temporal and spatial scales, it isnecessary to elucidate the mechanism using land surface and ecosystem models that are appropriate
for the target of interest. Clouds and aerosols are other important players in determining the Earth’s

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energy budget, but our knowledge is severely limited. To fill in the knowledge gaps, laboratory
experiments and observations to understand the microphysical processes of mixed-phase clouds are
particularly recommended. Studies on behaviors and radiation effects of clouds formed under various
conditions need to be conducted in terms of atmosphere-ocean and cloud-aerosol interactions.
Contributions of aerosols of anthropogenic and natural origin that act as cloud condensation nuclei(CCN) and ice nucleating particles (INP) also need to be studied. The role of wildfires over theNorthern Hemisphere on CO2 emission and the effect on clouds over the Arctic region would be
emerging scientific issues.
•Sea level change

The impact of sea level rise is global, and it brings large consequences to human society even thoughsome of its origins are in the Arctic. Glaciers have been contributing to the ongoing sea level rise, andthe contributions of ice sheets are increasingly important. To quantify and understand the mechanismof the mass loss of the Greenland ice sheet and glaciers in the Arctic, long-standing field observations,satellite remote sensing, and numerical modeling are essential. One important element that needs tobe achieved is the quantification of organic and inorganic impurities in snow and ice, and theevaluation of their impact on surface albedo and melting across Arctic glaciers. Ice sheets interact not
only with the atmosphere and ocean but also with the solid Earth. Thus, another important element is
the satellite-based analysis of regional crustal deformation, the development of an absolute gravimeter
network, and the development of high-resolution numerical models to reconstruct these observables.
Ice sheets are known to have long memories and to exhibit nonlinear dynamical behaviors associatedwith the so-called “tipping point”. To obtain a comprehensive understanding of the long-term
behaviors of the Greenland ice sheet, paleoclimatic studies based on both reconstruction and numericalmodeling of ice sheets, which are not necessarily limited to Greenland, would be very useful.
•Atmospheric linkage between the Arctic and mid-latitude

The Arctic is not an isolated system. It exchanges energy, moisture, and materials with mid-latitudes.
There is an intense debate over how much of the observed winter cooling in the recent decades at themid-latitude continent is attributable to the loss of sea ice in the Barents and Kara seas. Although thedebate is far from settled, it points out the potentially very important influence of Arctic climate change
on regions outside the Arctic. Such remote influence may be framed as the classical atmospheric“teleconnection”, but the involvement of the Arctic in the teleconnection theory is poorly established.
In that, the coupling between the troposphere and the stratosphere may also be important. Link
between extreme events and global-scale teleconnections requires a special attention. The interaction
between the Arctic and mid-latitude may also be understood in terms of modes of atmosphere-oceanvariability. Sustaining mechanism for modes of natural climate variability and their modulation under2

global warming has a high priority of research. To predict extreme events skillfully, the strategy ofsustaining the Arctic observing network and developing the modeling framework should be discussed.
It is worth stressing that it is important not only to strengthen the international Arctic researchcollaboration framework but also to strengthen the international research collaboration with the midlatitude or global research activity.
•Sea ice

Sea ice is a unique property of the polar regions (apart from some exceptional seas), but its change isat the heart of various global environmental changes as seen in the above discussions. The change in
sea ice is not only driven by the local energy balance at the top of the atmosphere but also influencedby atmospheric and oceanic heat transport to the Arctic. Extreme events may also be important as thetransport mechanism and the link between weather events and climate change requires specialattention. Sea ice prevents exchanges in energy, momentum, and materials between the atmosphereand the ocean. As to the momentum exchange, the interaction between sea ice and ocean surface waves
needs to be elaborated. The initialization of climate models to the current conditions plays a criticalrole in the relatively near-term future projection. Therefore, the establishment of an appropriateassimilation technique is important. For the long-term future projection, the poor reproducibility of
the current sea ice condition by climate models yields severe limitations to our prediction skills. In
either time scale, a reliable dataset of sea ice thickness is essential. In addition, process understandingof sea ice changes and its incorporation into the climate model representation is a high priority ofresearch. The fate of sea ice has a profound impact on the global environment which is a part of Arctic
warming amplification processes, and the integrative understanding of the mechanism for Arctic
amplification from a process-oriented viewpoint (e.g., laboratory experiment, in-situ observations, andnumerical modeling) to a macroscopic viewpoint (e.g., remote sensing, paleoclimate, numericalmodeling, and data assimilation) needs to be established.
Submitted together with:
JCAR (2024): Executive Summary of Long-term Plan for Arctic Environmental Research.
References:
Japan Consortium for Arctic Environmental Research (2024). Executive Summary of Long-term Planfor Arctic Environmental Research. https://www.jcar.org/e/longterm/
Japan Consortium for Arctic Environmental Research (2024). Long-term Plan for Arctic
Environmental Research. In press. [in Japanese]3