Climate Change And Its Impact On Cryosphere In The Central Himalayan Region

The Himalayas has the largest area of glacier coverage outside of the two poles and is known as the“Third Pole”in the world.15,000 glaciers produce inimitable water storage to give the genesis of numerous river systems like the Indus,the Brahmaputra and the Ganga,which supports 15%of the total population in India.In the past few decades,climate change has caused extensive melting and decline of glaciers in the Himalayas.In India,rapid population growth and people's changes to natural ecosystems have also become the main factors that accelerate climate change and environmental degradation.This change is particularly significant in mountain ecosystems.Due to its unique vertical height,high mountain regions are ideal areas for assessing climate change.Most of the central Himalayas are covered by undulating,rugged terrain and glaciers.Many major rivers originate in this area,such as the Ganga,Alaknanda,Yamuna,Bhilangana,etc.The basins of these rivers are the main source of fresh water in the downstream areas.In recent years,all major glaciers have shown a tendency to melt.The melting of glaciers in high-altitude mountainous areas will accelerate the occurrence of extreme events such as collapses,avalanches,landslides,glacier fragmentation,and floods caused by glacier eruptions.Glacier melting has also led to the formation and expansion of glacial lakes.If any kind of structural displacement occurs in these lakes,the water stored in the entire glacial lake will form a large-scale flood,leading to glacier lakes outburst floods(GLOFs),Known as"Jokulhlaups"(local term)in India,this is very common in the Himalayas,often causing a lot of physical damage,loss of life,property,and infrastructure,and its potential risks are greater.Climate change has led to shrinking glaciers,reducing snow cover,the emergence of new glacial lakes,or the expansion of glacial lakes,increasing the risk of flooding and related geological disasters.Although there have been some researches on climate change,snow cover dynamics,glacial lake formation,glacier fragmentation,and related geological disasters,previous studies have mainly focused on single issues,and lacked more extensive and systematic discussions on existing issues.Therefore,this study uses the Indian state of Uttarakhand in the central Himalayas as the research area,which is a sensitive area of climate change,but there is still a lack of research on the relationship between climate change and humans.This study uses long-time series satellite image data,advanced numerical models and high-precision ground data to research climate dynamics and their possible impacts,such as snow cover changes,glacier retreat and fragmentation,glacial lake formation,lake eruption floods Danger,further explored the response of glacier dynamics to climate change and human activities,which has important scientific value and practical significance.The present study includes the following research questions to identify the impacts of climate change on the Himalayan cryosphere 1)What are the major trends of climate change?2)How the snow cover and glacier lakes were influenced by the climatic uncertainties?3)What are the change-induced geo-environmental problems?This study further includes four objectives 1)To map spatial distribution and trends of monthly,annual,and seasonal SCA,rainfall and temperature using observed and satellite data products 2)To establish the relationship between snow cover,temperature,rainfall,and river discharge 3)To identify the Spatio-temporal extent of glacier lakes and outburst flood 4)To explore the relationship between climate change and associated geo-hazards and suggest suitable measures for minimizing the possible impacts.To achieve these objectives,primary data were collected through intensive field surveys(GPS surveys)and secondary data from several concerned agencies.Seven village-level questionnaires surveys have been conducted for gathering human perceptions regarding climate change,lake outburst flood and landslide hazards also anticipate during any natural calamities of 120respondents,and two surveys were done at upper reaches of the valley(Glacier visits).In addition,GDEM data was utilized to investigate the terrain and its influence on the snow cover dynamics.Station-based observed data of rainfall and temperature were taken from India Meteorological Department and CHIRPS,PERSIANN-CDR and MODIS LST gridded datasets were also used for using GEE web-based platform.Several descriptive and non-parametric statistics,spectral reflectance modeling,the GEE algorithms,GLOFs modeling and HEC-RAS were used to conduct the entire research.Key findings of this study:1.Elevation-dependent investigation of Uttarakhand Himalaya using MODIS Terra SCA and LST indicated an increasing temperature trend(0.7°C/decade)at upper elevations,while slightly cooler condition(-0.01°C/decade)was found at a lower elevation with an increase in snow cover(6 sq.km/decade,r~2=0.79)during the pre-monsoon season.Moreover,the micro-level investigation in the Bhilangana valley indicated a similar increasing trend of mean annual temperature using observed data sets(0.6°C/decade).2.Rainfall analysis using station data in the Bhilangana basin highlights declining trends within the last 46 years(-12.2mm/decade)along with an increasing temperature trend(0.6°C/decade).However,the macro-level study on the Uttarakhand Himalayan region revealed an increasing trend(averaging,25mm/decade)in recent years with an increased frequency of extreme rainfall events,which is further supported by the micro-level field investigation and extreme weather conditions after the dry period of 2008.Elevation-dependent investigation of Uttarakhand Himalaya exhibits maximum precipitation at lower-elevated regions(45mm/decade)caused appears to be a marginal increase in annual snow cover across lower elevations(6 sq.km/decade),however,higher-elevated regions witnessed annual reductions in SCA(-75 sq.km/decade)with relatively fewer precipitation(-25mm/decade).3.Snow cover extent using Landsat data in the Bhilangana basin reveals decreased snow cover area(about 110 sq.km/decade)in the last two decades over 3600m elevation.However,macro-level study on the entire Uttarakhand Himalaya at different elevations using MODIS data specifies,enlarged snow cover area at lower elevation zones(<2000m elevation)due to increased precipitation(45mm/decade)(r~2=0.82),and upper elevation areas perceived similar declined trend(-75sq.km/decade)with Landsat data along with an increased temperature(0.07°C/decade).4.The important glaciers of the Bhilangana valley have experienced is almost 2 km. retrograde movement in the last few decades.The study further noticed the formation of tributary glaciers and their prompt fragmentation(100m/decade),which accelerate the formation of new glacier lakes in the last few decades.5.The warming of the climate has formed many new glacial lakes and has expanded the area averaging,(13397 to 269078 sq.m),volume(75406 to 5339006 sq.m)and depth(5.63 to 19.84m)in the last 10-years.A total of 14 glacier lakes were mapped in the micro-level analysis,out of them single lake has been treated as potentially dangerous for future flood hazards with increased peak discharge(13.18 to 230.39 m~3/s)in last 10-years.Additionally,numerous geo-hazards i.e.landslides,riverbank erosion,and glacier fragmentation were also investigated.The study shows more than 120 sq.km area of the study domain witnessed high landslide risk.6.The melting of glaciers and the formation and expansion of glacial lakes caused by global climate change are very common in the central Himalaya.The temperature rise has led to the formation of new glacial lakes and changes in snow-covered areas.Moreover,this area is located in an earthquake-prone area,and many large and small earthquakes will aggravate the outburst of ice lakes and cause a large number of flood events.However,micro to macro-level mitigation strategies can minimize future risk.