Yoshihiro Iijima

• Doctor of Science
• Professor at Tokyo Metropolitan University

Permafrost and ground freezing/thawing processes are physically and eco-climatologically important factors in the terrestrial cryosphere. The model reproducibility of frozen ground affects the certainty and reliability of simulated eco-climate conditions in cold regions as well as on a global scale. This study evaluated the variations and their att...

As a result of climate change, the pan-Arctic region has seen greater temperature increases than other geographical regions on the Earth’s surface. This has led to substantial changes in terrestrial ecosystems and the hydrological cycle, which have affected the distribution of vegetation and the patterns of water flow and accumulation. Various remo...

Thermokarst development is a topographic change in the landscape that is commonly associated with permafrost degradation in ice-rich permafrost regions. The Lena-Aldan interfluvial area in Central Yakutia in eastern Siberia has undergone extensive thermokarst development in the last three decades, particularly in the vicinity of settlements. Despit...

A simple stochastic representation of the spatial variability in thaw depth is proposed. Thaw depth distribution measured in the two larch‐type forests in eastern Siberia, Spasskaya Pad and Elgeeii, showed different spatial, seasonal, and interannual variability, respectively. Year‐to‐year variation in active‐layer thickness was minor in Spasskaya...

Rice lodging causes a loss of yield and leads to lower-quality rice. In Japan, Koshihikari is the most popular rice variety, and it has been widely cultivated for many years despite its susceptibility to lodging. Reducing basal fertilizer is recommended when the available nitrogen in soil (SAN) exceeds the optimum level (80–200 mg N kg⁻¹). However,...

Greenness indices derived from near-surface photography are increasingly being used for the continuous and automated monitoring of vegetation within various ecosystems. In the present study, we examined the characteristics and applicability of the green chromatic coordinate (GCC) index for monitoring vegetation parameters in semi-arid grasslands. F...

This paper presents the results of 30 years of permafrost thermal monitoring in the Tiksi area in the eastern Russian Arctic. At a stone ridge site, the mean annual temperatures in the upper 30 m of the ground have increased by 1–2.4 °C compared to the first years of observations, with trends of °C/yr. At the same time, its change was uneven. In th...

Rapid Arctic warming has altered the regional hydrological cycle through reduction in Arctic sea ice. Observational and modeling efforts provided evidence that the enhanced evaporation from the Arctic Ocean could increase snowfall over high latitude terrestrial zones. However, questions remain regarding the amount of equatorward moisture transport...

Forest fires significantly impact permafrost degradation in the subarctic regions. However, interannual and seasonal variations in surface deformation due to permafrost thawing in burned areas were poorly understood. Measuring the ground surface displacement in fire scars helps us understand the freeze‐thaw dynamics of near‐surface ground and predi...

Thermokarst is a typical process that indicates widespread permafrost degradation in yedoma landscapes. The Lena-Aldan interfluvial area in Central Yakutia in eastern Siberia is now facing extensive landscape changes with surface subsidence due to thermokarst development during the past few decades. To clarify the spatial extent and rate of subside...

The purpose of this article was to compile four separate digital thematic maps of temperature and ice content of permafrost, the active layer thickness, and cryogenic processes in Yakutia as a basis for assessing changes to modern climate changes and anthropogenic disturbances. In this work, materials on permafrost were used, serving as the basis f...

This paper focuses on the uncertainty of summer precipitation estimations produced by Global Satellite Mapping of Precipitation (GSMaP) over Mongolia, a region that has complex terrain and sparse weather observation networks. We first compared average summer precipitation over Mongolian territory as reported by several precipitation products. Altho...

This book is an attempt to understand the impact of Climate Change on the Arctic human societies from the indigenous perspectives, by focusing on the peoples living in the Republic of Sakha (Yakutia) of the Russian Federation. Historically, and also today, the livelihood of the Sakha people is closely related to permafrost. Scientific evidence show...

Obtaining a better understanding of groundwater dynamics in permafrost zones is a critical issue in permafrost hydrology. This includes assessing the impacts of climate change on permafrost thaw and ground ice-melt. Both permafrost thaw and ground ice-melt can be related to groundwater discharges (i.e. spring discharges), and spring water is an imp...

Surface water monitoring with fine spatiotemporal resolution in the subarctic is important for understanding the impact of climate change upon hydrological cycles in the region. This study provides dynamic water mapping with daily frequency and a moderate (500 m) resolution over a heterogeneous thermokarst landscape in eastern Siberia. A combinatio...

Permafrost plays a hugely significant role in sustaining the global climate for many reasons. As it thaws, gases (usually methane and carbon dioxide) that have lain trapped underneath the ice for millennia are released. These gases then enter the atmosphere and accelerate global warming which leads to more permafrost degradation and it eventually b...

River runoff from the four largest Siberian river basins (the Ob, Yenisei, Lena, andKolyma) considerably contributes to freshwater flux into the Arctic Ocean from the Eur-asian continent. However, the effects of variation in snow cover fraction on the eco-hydrological variations in these basins are not well understood. In this study, weanalysed the...

In recent years, extreme cold air outbreak events (COEs) in winter have tended to occur more frequently over the mid‐latitudes of Eurasia, including Mongolia, despite marked warming across the continent. In the 2000s, an increase in COEs contributed to huge losses of livestock throughout Mongolia, causing socioeconomic stagnation. This study diagno...

Grazing is a key factor in grassland disturbance that affects plant biomass, soil properties, and carbon exchange in grasslands. The objective of this study was to quantitatively evaluate the effects of grazing on grassland ecosystems in Mongolia. To this end, we developed a new method for determining the actual and quantitative livestock effects....

This book is an attempt to understand the impact of global warming on human societies in the Arctic/North in terms of the local peoples and cultures, or from the indigenous perspectives, by focusing on the peoples living in the Republic of Sakha (Yakutia) of the Russian Federation. Different lifestyles exist in the modern Arctic: the indigenous peo...

Eastern Siberia is located at the centre of a continuous permafrost zone. The most prominent feature of this zone is its vast cover by deciduous coniferous boreal (taiga) forest. Underlying the boreal ecosystem is an extensive and massive ice layer within the permafrost (Yedoma), which was crucial for the development of large ground subsidence duri...

Differentiating thermokarst basin sediments with respect to the involved processes and environmental conditions is an important tool to understand permafrost landscape dynamics and scenarios and future trajectories in a warming Arctic and Subarctic. Thermokarst basin deposits have complex sedimentary structures due to the variability of Yedoma sour...

This study investigated the CO2 exchange over a 10-year period (2005–2014) inside and above a larch-dominant forest in the central Lena river basin, eastern Siberia. A wet-soil condition, such as that found in the active layer (seasonally thawed soil layer of upper permafrost), containing unusually high soil water close to saturation and partial su...

This book discusses the water and carbon cycle system in the permafrost region of eastern Siberia, providing vital insights into how climate change has affected the permafrost environment in recent decades. It analyzes the relationships between precipitation and evapotranspiration, gross primary production and runoff in the permafrost regions, whic...

Large negative temperature anomalies due to cold air advection have been observed over the Eurasian continent in recent years. During the 2009/2010 winter, a large amount of snow accumulated across Central Asia and China, which along with a strong cold air outbreak, resulted in extremely high livestock mortality in Mongolia. The present study exami...

Eastern Siberia is characterized by widespread permafrost thawing and subsequent thermokarst development. Estimation of the impacts of the predicted rise in precipitation and air temperatures under climate change requires quantitative knowledge about the spatial distribution of thermokarst development. In the last few years, unmanned aerial systems...

Mosses strongly affect water and heat fluxes due their high water holding capacity and the provision of insulation. A land surface model (the coupled hydrological and biogeochemical process model, CHANGE) was used to quantitatively assess the influence of moss cover on soil temperature (TSOIL), active layer thickness (ALT), and ecosystem carbon bal...

The Arctic freshwater budget is critical for understanding the climate in the northern regions. However, the hydrology of the Arctic circumpolar tundra region (ACTR) and the largest pan-Arctic rivers are still not well understood. In this paper, we analyze the spatiotemporal variations in the terrestrial water storage (TWS) of the ACTR and three of...

An Arctic terrestrial model intercomparison project (GTMIP), designed for enhanced collaborations between modeling and field scientists, and for assessment of uncertainty and variations in current terrestrial models to improve, was carried out with 21 domestic and international participants, ranging from physical to biogeochemical to hybrid models....

The Arctic freshwater budget is critical for understanding the climate in the northern regions. However, the hydrology of the Arctic circumpolar tundra region (ACTR) and the largest pan-Arctic rivers are still not well understood. In the present paper, we analyze the spatiotemporal variations in terrestrial water storage (TWS) of the ACTR, includin...

Carbon dioxide (CO2) fluxes by different methods vary largely at global, regional and local scales. The net CO2 fluxes by three bottom-up methods (tower observation (TWR), biogeochemical models (GTM), and a data-driven model (SVR)), and an ensemble of atmospheric inversions (top-down method, INV) are compared in Yakutsk, Siberia for 2004-2013. The...

Keywords: temperature, active and seasonally frozen ground, site-specific factors Factors that contribute on permafrost degradation are anthropogenic disturbances, including overgrazing, forest clear-cutting and forest fires. The forests are distributed in a mosaic pattern and overlap considerably the permafrost regions in central Mongolia; river d...

Keywords: the Altai and Khentii mountains; permafrost monitoring; Mongolia In Mongolia, permafrost predominantly occurs in the Altai, Khuvsgul, Khangai, and Khentii Mountains and their surrounding areas where the southern boundary of the Siberian permafrost is roughly located. During the last several years numerous permafrost monitoring sites were...

In a context of scientific and public debates on permafrost degradation under global climate change, this article provides an integrated review and analysis of environmental and socio-economic trends in a subarctic region. It focuses on Sakha (Yakut) animal husbandry as an example of indigenous land use. Within Sakha-Yakutia’s boreal forests, anima...

The Central Yakutian permafrost landscape is rapidly being modified by land use and global warming, but small-scale thermokarst process variability and hydrological conditions are poorly understood. We analyze lake-area changes and thaw subsidence of young thermokarst lakes on ice-complex deposits (yedoma lakes) in comparison to residual lakes in a...

Active-layer thickness (ALT) is one of the most robust measures used to assess the impact of climate change on terrestrial permafrost. Testing of a handheld dynamic cone penetrometer showed that it was capable of measuring ALT with the same level of accuracy as conventional methods in boreal and tundra sites in eastern Siberia. The penetrometer als...

Ice-wedges are common permafrost features formed over hundreds to thousands of years of repeated frost cracking and ice vein growth. We used field and remote sensing observations to assess changes in areas dominated by ice-wedges, and we simulated the effects of those changes on snow accumulation and runoff. We show that top melting of ice-wedges a...

Ice wedges are common features of the subsurface in permafrost regions. They develop by repeated frost cracking and ice vein growth over hundreds to thousands of years. Ice-wedge formation causes the archetypal polygonal patterns seen in tundra across the Arctic landscape. Here we use field and remote sensing observations to document polygon succes...

In the last decade, increases in both soil temperature and active layer thickness have been observed in the central Lena River basin, an area located in the centre of continuous permafrost in the Eurasian continent. Increased soil temperatures have been accompanied by corresponding increases in soil moisture within the active layer at many sites th...

Here, the authors describe the construction of a forcing data set for land surface models (including both physical and biogeochemical models; LSMs) with eight meteorological variables for the 35-year period from 1979 to 2013. The data set is intended for use in a model intercomparison study, called GTMIP, which is a part of the Japanese-funded Arct...

Here, the authors describe the construction of a forcing data set for land surface models (including both physical and biogeochemical models; LSMs) with eight meteorological variables for the 35-year period from 1979 to 2013. The data set is intended for use in a model intercomparison study, called GTMIP, which is a part of the Japanese-funded Arct...

Central Yakutian permafrost landscapes are subject to rapid modifications as a result of intensive land use, extreme weather, and the current global warming. With regard to the predicted increase in precipitation and temperature due to climate change, understanding the spatio-temporal variability of thermokarst processes is required. Regionally, we...

Top melting of ice-wedges and subsequent ground subsidence is now a widespread phenomenon across the Arctic domain. We show field and remote sensing observations that document extensive ice-wedge degradation, which initially has resulted in increased wetness contrast across the landscape (i.e. both a drying and a wetting), a shift in pond type and...

International Arctic Systems for Observing the Atmosphere (IASOA) activities and partnerships were initiated as a part of the 2007-09 International Polar Year (IPY) and are expected to continue for many decades as a legacy program. The IASOA focus is on coordinating intensive measurements of the Arctic atmosphere collected in the United States, Can...

As part of the terrestrial branch of the Japan-funded Arctic Climate Change Research Project (GRENE-TEA), which aims to clarify the role and function of the terrestrial Arctic in the climate system and assess the influence of its changes on a global scale, this model intercomparison project (GTMIP) is designed to (1) enhance communication and under...

Here, the authors describe the construction of a forcing dataset for Land Surface Models (including both physical and biogeochemical models; LSMs) with eight meteorological variables for the 35 year period from 1979 to 2013. The dataset is intended for use in a model intercomparison (MIP) study, called GTMIP, which is a part of the Japanese-funded...

In the last two decades the major focus of study in forest water and carbon balances in eastern Siberia has been on the effect of rain during the growing season. Little attention has been paid to the contribution of snowmelt water. The results of the present study indicate that weather conditions during the snowmelt period as well as the soil moist...

Permafrost underlying forested north-facing slopes and seasonally frozen ground underlying mountain steppes on south-facing slopes co-exist within a small mountain basin that represents the most general landscape type in northern central Mongolia. A 5-year time series of hydro-meteorological parameters on these slopes is presented in order to ident...

In the last two decades, anthropogenic climatic change has resulted in increased cryogenic activity in northeastern Eurasia, with adverse consequences for landscapes and socio-economic systems in the permafrost zone. The main purpose of this study was to assess the recent phases of warming, starting with Arctic warming. We performed a spatiotempora...

Water vapour and carbon dioxide fluxes, as well as environmental factors, were measured in an Eastern Siberian larch forest for 14 years from 1998 to 2011 to understand the water and carbon balances and the effects of environmental variables on these balances in this region. The overstory vegetation in this forest has been damaged by the unusual wa...

Permafrost degradation and changes in water balance in a thermokarst lake in the middle part of the Lena River basin in eastern Siberia were investigated. We analysed the role of permafrost thawing in the water balance of a growing thermokarst lake. Long-term observations during the last two decades (1992–2008) at our thermokarst monitoring site, Y...

Continuous observation over the last decade has revealed evidence of abrupt land surface moistening as well as rapid soil warming within the active layer and upper part of permafrost within the central Lena River basin in eastern Siberia. The present study examined the relationship between permafrost degradation and ecohydrological change in this r...

Isotopic composition of atmospheric water vapour (δ18OV) was observed at a larch forest near Yakutsk in eastern Siberia during the late summer periods of 2006, 2007 and 2008. The δ18OV [and deuterium excess (d-excess)] values observed in 2006 and 2008 positively (and negatively) correlated with mixing ratio of atmospheric water vapour, whereas, in...

The results of 16 years of seasonal thaw depth observations in permafrost landscapes near Yakutsk have been presented. For the first time in Central Yakutia, the observations at two sites have been carried out following the CALM program protocol on a dense grid of frost/thaw tubes. Measurements have provided new data on the effects of landscape con...

Artificial warming experiments on alpine, subalpine, boreal, and subboreal ecosystems are reviewed to understand the impacts of global warming on the ecosystems of these regions. Among various warming methods, passive warming methods, especially open top chambers （OTC） , have mainly been used in these outland regions due to limited electricity supp...

Deciduous forest covers vast areas of permafrost under severe dry climate in eastern Siberia. Understanding the water cycle in this forest ecosystem is quite important for climate projection. In this study, diurnal variations in isotopic compositions of atmospheric water vapour were observed in eastern Siberia with isotope analyses of precipitation...

Wet climate with largely increased in precipitation during summer and snow accumulation during winter had continued 4 years since 2004 winter in eastern Siberia. Soil moisture in the active layer had been significantly increased corresponding with thawing of permafrost near the surface during following years. The perennially water-logged active lay...

This study not only examined the spatiotemporal variations of active-layer thickness (ALT) in permafrost regions during 1948-2006 over the terrestrial Arctic regions experiencing climate changes, but also identified the associated drivers based on observational data and a simulation conducted by a land surface model (CHANGE). The focus on the ALT e...

This study not only examined the spatiotemporal variations of permafrost active layer thickness (ALT) during 1948–2006 over the terrestrial Arctic regions experiencing climate changes, but also identified the associated drivers based on observational data and a simulation conducted by a land surface model (CHANGE). The focus on the ALT extends prev...

In the mountainous regions of northern Mongolia, there are peculiar different patches of the landscape "ecotone" with north-facing forest slope and south-facing grassland slope. The slopes are distinguished as marked contrast of permafrost distribution as well. The present study revealed ecohydrological processes in terms of evapotranspiration and...

Complete description of the model CHANGETo assess the model performance for water, energy and CO2 fluxesInformative responses of larch forest to climate change

The application of automated temperature recorders (temperature data loggers) in thermal monitoring of upper permafrost is examined. Based on the results of 10 years of use of temperature data loggers in Yakutia, the recommendations are provided on the choice and preparation of data loggers for monitoring studies, and a description is given for sel...

Recently, our continuous observations during the last decade revealed considerable evidence of abrupt land surface moistening and synchronized rapid soil warming within active layer and upper part of permafrost in the central Lena River basin in eastern Siberia. The present study focuses firstly on the linkage between atmospheric and land surface v...

The terrestrial Arctic regions have been experienced a set of various changes due to climatic changes and human activities. The significant changes include increased river discharge, permafrost reduction, early snowmelt, etc. Among them, the early snowmelt caused by the increased temperature is sequentially linked to vegetation phenology and hydrol...

Marked increases in active-layer and upper permafrost temperatures occurred in the central Lena River basin in association with abrupt increases in active-layer soil moisture following the summer of 2005. The positive trend in soil temperature-moisture relations was observed at monitoring sites in the Yakutsk area, regardless of vegetation and soil...

The hydrological conditions have been changing quite much in the Northern Eurasia due as a part of so called ``global warming'', and abrupt change of Arctic Ocean and atmospheric response according to this change. And these changes are related to the hydrological conditions of the large Arctic draining rivers and affecting them. The large scale con...

Wide-ranging environmental changes have been documented for the Arctic over the last few decades. The documents suggest that the Arctic is experiencing changes never seen in historic times. The physical, biological, and chemical components of the Arctic system are interrelated through a network of linkage, feedbacks, and multi-dependent interaction...

We examined the hydroclimatic conditions during the last decade on Chichi-jima in the Ogasawara (Bonin) Islands using climatic data (1998-2007) recorded at the Chichi-jima observatory. Climatological wetness indexes (precipitation/ potential evaporation) were approximately 1.0 from 1998 to 2001, indicating closely balanced dry and wet conditions, w...

Water vapor, energy fluxes, and environmental conditions were measured in an eastern Siberian larch forest for 7 water years, from 1998 to 2006, to understand the water-balance characteristics and interannual variation (IAV). The latent heat flux accounted for 38-67% of the sum of turbulent heat fluxes in June, July, and August, a relatively modera...

A land surface model was developed to evaluate the dynamics of water, energy, and CO2 fluxes in the soil- vegetation-atmosphere system of the Arctic regions. The model includes three submodels: vegetation, snow cover, and soil. The energy budgets are solved for the radiative and energy fluxes both at the canopy layer and the soil surface. The snow...

In drylands, water deficit is the primary factor limiting plant growth. In the present study, surface energy balance and plant growth (above-ground and below-ground biomass) were measured continuously during the 2002 growing season in semiarid grassland in the northern part of Kazakhstan, Central Asia. Although there was above normal total rainfall...

Since 2002, long-term field research of joint Japan-Mongolian IORGC projects have been concentrated and conducted in Nalaikh and in Terelj near Ulaanbaatar, Mongolia. There are two sites in Terelj (Terelj GL, Terelj FA) and one site in Nalaikh. At these sites we have been measuring the meteorological and permafrost parameters. This paper presents t...

In the present study, we examine the climatological features and interannual variations in snow disappearance within the Lena River Basin, Eastern Siberia, during a recent 15-year period (1986–2000), and the relationship of snow disappearance to atmospheric conditions. According to the climatology of the day of the year on which snow disappears, th...

We examined the long-term change in the hydroclimatic environment during the 20th century on Chichi-jima in the Ogasawara Islands using monthly climatic data observed at the Chichi-jima Observatory over 78 years: 1907-1943, 1951-1959, and 1969-2000. The mean annual temperature for 1907-1943 was about 0.4-0.6°C lower than that for 1951-1959 and 1969...

The present study investigated atmospheric conditions producing summer-time nocturnal cooling in high mountain areas of central Japan. The focus was on the cold-air pool observed in a small hollow in the Yatsugatake range during 1997. Differences in cooling mechanisms between the high mountains and lower plains/basins were examined in terms of atmo...

Although the climatic environment has not been quantified, it is commonly believed that subtropical dry scrub is distributed in the dryer areas of Chichijima Island in the Ogasawara (Bonin) Islands, the northwestern Pacific. To clarify the hydroclimatic conditions of subtropical dry scrub, year-round atmospheric and soil moisture observations were...

Seasonal differences in the longwave radiation balance, diurnal cycles of humidity and cloudiness, and ambient winds during the warm season were evaluated to determine their effect on the nocturnal cooling processes of a high mountain hollow in central Japan. This hollow is located at an elevation of 2230 m at the bottom, having a depth of 50-200 m...

An observational study has been conducted into the seasonal characteristics of the cold-air pool formation in a hollow in the subalpine area of the Yatsugatake Range during the warm seasons from 1995 through to 1997. The uniqueness of the present study is a detection of seasonal differences in the formation processes based on a 3-year observation....

The present study focuses on the warm season temperature conditions in a small hollow of Mt. Inako-dake, Yatsugatake Range, central Japan, where an interesting vertical structure of vegetation is observed. Here, alpine plants (Pinus pumila community) are located at the bottom (ca. 2, 300m a.s.l.) and a subalpine forest is formed above them (so-call...

To predict the influence of global warming on high-mountain plants, we have started an experiment on Mt. Kisokomagatake (2956 m), the Central Japanese Alps, using the ITEX (International Tundra Experiment) method. Four small greenhouses (OTC: open-top-chamber) were set up in May 1995 to cover two alpine species: Arctous alpinus var. japonica and Di...

We evaluated symbiotic system of forest and permafrost using land-surface hydro-meteorological datasets obtained at northern Mongolia, southern boundary of Eurasian permafrost. Analysis indicated that greatly reduced radiation by forest shading is fundamental agent for permafrost preservation underneath northern forested slopes. Furthermore, organi...

Geographical variations in nocturnal cooling are investigated using statistical analyses of routine observational data in central Japan. Seasonal variations in the relationships between nocturnal cooling intensity and topographic features are investigated in terms of synoptic atmospheric conditions and derived mesoscale circulation. Cluster analysi...

According to past studies based on long-term variations in precipitation and air temperature, climate in Chichi-jima of the Bonin (Ogasawara) Islands was rather wetter during the first half of the 20th century than during the latter half through present. The present study revealed actual hydroclimatic conditions using detailed meteorological compon...

Subtropical dry scrub is widely distributed on Ani-jima (Ani-jima Island) and includes rare endemic plant species of the Ogasawara Islands, northwestern Pacific. In this study, we evaluated the hydroclimatic conditions that affect the establishment of subtropical dry scrub on Ani-jima. We have conducted continuous meteorological observations at Ani...