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Remote Sensing of Climatic and Environmental Changes over the Antarctic, Arctic, and the Qinghai-Tibet Plateau

A special issue of Remote Sensing (ISSN 2072-4292). This special issue belongs to the section "Environmental Remote Sensing".

Deadline for manuscript submissions: closed (31 March 2020) | Viewed by 62757

Special Issue Editors

Prof. Tao Che

E-Mail Website
Guest Editor
Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 73000, China
Interests: snow cover; remote sensing; data assimilation; hydrology in cold region
Prof. Dr. Xinwu Li

E-Mail Website
Guest Editor
Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing 100094, China
Interests: glacier; vegetation; remote sensing; environmental change
Prof. Laurent Ferro-Famil

E-Mail Website
Guest Editor
Institute of Electronics and Telecommunications of Rennes, University of Rennes 1, 263, Av. Leclerc Campus Beaulieu, Bât 11D, 35042 Rennes, FranceCESBIO, 18 Av Belin, BPI 2801, 31401 Toulouse, France
Interests: EM and radar imaging; SAR tomography; signal processing; snow remote sensing; inverse problems
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The Antarctic, Arctic, and the Qinghai-Tibet Plateau (QTP, the so-called Third Pole) have been undergoing unprecedented changes in climate and environment. Extensive research has been conducted either on single processes (such as the cryosphere, climate, hydrology, biogeoscience and ecosystems), or individual regions. Integrated studies are essential and expected to advance our understanding on the potential linkage and interaction among the Three Poles. Remote sensing is capable to provide long-term observational data in large scale, which has great potential to investigate the Three Poles as an entirety.
This Special Issue is seeking integrated research on climatic and environmental changes over the Three Poles, especially coupled processes and the teleconnection, synchronization, and asynchronization among regions, as well as the changes induced over other regions in the earth system. Examples include but are not limited to the contradictive sea ice changes found in the Arctic and Antarctic; sea level rising due to the retreat of the Antarctic sheet, Greenland sheet and the glaciers; snow and ice albedo feedbacks; the freeze/thaw of permafrost and melting of snow and ice; and the spatio-temporal changes of vegetation in the Three Poles.
The Special Issue will also facilitate cross-cutting research on data-model integration, interactions of multiple-spheres of the earth system, and the environmental changes in other regions induced by changes in the Three Poles. New methods/technologies, reviews and future perspectives are also encouraged for submission.

Prof. Tao Che
Prof. Xinwu Li
Prof. Laurent Ferro-Famil
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Remote Sensing is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Remote sensing
  • Arctic
  • Antarctic
  • Tibet Plateau
  • Cryosphere
  • Ecosystem
  • Environment
  • Climate change

Published Papers (18 papers)

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26 pages, 14774 KiB  
Article
Assessing Snow Phenology over the Large Part of Eurasia Using Satellite Observations from 2000 to 2016
by Yanhua Sun, Tingjun Zhang, Yijing Liu, Wenyu Zhao and Xiaodong Huang
Remote Sens. 2020, 12(12), 2060; https://doi.org/10.3390/rs12122060 - 26 Jun 2020
Cited by 14 | Viewed by 3101
Abstract
Snow plays an important role in meteorological, hydrological and ecological processes, and snow phenology variation is critical for improved understanding of climate feedback on snow cover. The main purpose of the study is to explore spatial-temporal changes and variabilities of the extent, timing [...] Read more.
Snow plays an important role in meteorological, hydrological and ecological processes, and snow phenology variation is critical for improved understanding of climate feedback on snow cover. The main purpose of the study is to explore spatial-temporal changes and variabilities of the extent, timing and duration, as well as phenology of seasonal snow cover across the large part of Eurasia from 2000 through 2016 using a Moderate Resolution Imaging Spectroradiometer (MODIS) cloud-free snow product produced in this study. The results indicate that there are no significant positive or negative interannual trends of snow cover extent (SCE) from 2000 to 2016, but there are large seasonal differences. SCE shows a significant negative trend in spring (p = 0.01) and a positive trend in winter. The stable snow cover areas accounting for 78.8% of the large part of Eurasia, are mainly located north of latitude 45° N and in the mountainous areas. In this stable area, the number of snow-covered days is significantly increasing (p < 0.05) in 6.4% of the region and decreasing in 9.1% of the region, with the decreasing areas being mainly located in high altitude mountain areas and the increasing area occurring mainly in the ephemeral snow cover areas of northeastern and southern China. In central Siberia, Pamir and the Tibetan Plateau, the snow onset date tends to be delayed while the end date is becoming earlier from 2000 to 2016. While in the relatively low altitude plain areas, such as the West Siberian Plain and the Eastern European Plain region, the snow onset date is tending to advance, the end date tends to be delayed, but the increase is not significant. Full article
(This article belongs to the Special Issue Remote Sensing of Climatic and Environmental Changes over the Antarctic, Arctic, and the Qinghai-Tibet Plateau)
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29 pages, 21007 KiB  
Article
Basal Channel Extraction and Variation Analysis of Nioghalvfjerdsfjorden Ice Shelf in Greenland
by Zemin Wang, Xiangyu Song, Baojun Zhang, Tingting Liu and Hong Geng
Remote Sens. 2020, 12(9), 1474; https://doi.org/10.3390/rs12091474 - 6 May 2020
Cited by 8 | Viewed by 3029
Abstract
The ice shelf controls the ice flow and affects the rates of sea level rise. Its stability is affected by the basal channel to some extent. However, despite its importance, high spatiotemporal variation in the length of the basal channels and influencing factors [...] Read more.
The ice shelf controls the ice flow and affects the rates of sea level rise. Its stability is affected by the basal channel to some extent. However, despite its importance, high spatiotemporal variation in the length of the basal channels and influencing factors remain poorly characterized. Here, we present evidence from satellite and airborne remote-sensing for the basal channel beneath the floating Nioghalvfjerdsfjorden (79 North Glacier) ice shelf in Northeast Greenland. We observe the surface depression of the ice shelf using IceBridge, which is an ongoing NASA mission to monitor changes in polar ice. We find that the basal channel corresponds with the depression. Temporal and spatial changes of the basal channels from 2000 to 2018 are obtained annually. The results show that the main influencing factor affecting the basal channel is the sea surface temperature (SST), and the major area of the channel length change is found in the midstream area of the ice shelf. Full article
(This article belongs to the Special Issue Remote Sensing of Climatic and Environmental Changes over the Antarctic, Arctic, and the Qinghai-Tibet Plateau)
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21 pages, 7864 KiB  
Article
Interannual Variations of TOA Albedo over the Arctic, Antarctic and Tibetan Plateau in 2000–2019
by Dong L. Wu, Jae Nyung Lee, Kyu-Myong Kim and Young-Kwon Lim
Remote Sens. 2020, 12(9), 1460; https://doi.org/10.3390/rs12091460 - 5 May 2020
Cited by 5 | Viewed by 2732
Abstract
Recent changes in Earth’s climate system have significantly affected the radiation budget and its year-to-year variations at top of the atmosphere (TOA). Observing high-latitude TOA fluxes is still challenging from space, because spatial inhomogeneity of surface/atmospheric radiative processes and spectral variability can reflect [...] Read more.
Recent changes in Earth’s climate system have significantly affected the radiation budget and its year-to-year variations at top of the atmosphere (TOA). Observing high-latitude TOA fluxes is still challenging from space, because spatial inhomogeneity of surface/atmospheric radiative processes and spectral variability can reflect sunlight very differently. In this study we analyze the 20-year TOA flux and albedo data from CERES and MISR over the Arctic, the Antarctic, and Tibetan Plateau (TP), and found overall great consistency in the TOA albedo trend and interannual variations. The observations reveal a lagged correlation between the Arctic and subarctic albedo fluctuations. The observed year-to-year variations are further used to evaluate the reanalysis data, which exhibit substantial shortcomings in representing the polar TOA flux variability. The observed Arctic flux variations are highly correlated with cloud fraction (CF), except in the regions where CF > 90% or where the surface is covered by ice. An empirical orthogonal function (EOF) analysis shows that the first five EOFs can account for ~50% of the Arctic TOA variance, whereas the correlation with climate indices suggests that Sea Ice Extent (SIE), North Atlantic Oscillation (NAO) and 55°N–65°N cloudiness are the most influential processes in driving the TOA flux variabilities. Full article
(This article belongs to the Special Issue Remote Sensing of Climatic and Environmental Changes over the Antarctic, Arctic, and the Qinghai-Tibet Plateau)
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14 pages, 2180 KiB  
Article
Direct and Lagged Effects of Spring Phenology on Net Primary Productivity in the Alpine Grasslands on the Tibetan Plateau
by Zhoutao Zheng, Wenquan Zhu and Yangjian Zhang
Remote Sens. 2020, 12(7), 1223; https://doi.org/10.3390/rs12071223 - 10 Apr 2020
Cited by 23 | Viewed by 3633
Abstract
As a key biotic factor, phenology exerts fundamental influences on ecosystem carbon sequestration. However, whether spring phenology affects the subsequent seasonal ecosystem productivity and the underlying resource limitation mechanism remains unclear for the alpine grasslands of the Tibetan Plateau (TP). In this study, [...] Read more.
As a key biotic factor, phenology exerts fundamental influences on ecosystem carbon sequestration. However, whether spring phenology affects the subsequent seasonal ecosystem productivity and the underlying resource limitation mechanism remains unclear for the alpine grasslands of the Tibetan Plateau (TP). In this study, we investigated the direct and lagged seasonal responses of net primary productivity (NPP) to the beginning of growing season (BGS) along a precipitation gradient by integrating field observations, remote sensing monitoring and ecosystem model simulations. The results revealed distinct response patterns of seasonal NPP to BGS. Specifically, the BGS showed a significant and negative correlation with spring NPP (R = −0.73, p < 0.01), as evidenced by the direct boosting effects of earlier BGS on spring NPP. Moreover, spring NPP was more responsive to BGS in areas with more annual precipitation. The boosting effects of earlier BGS on NPP tended to weaken in summer compared with that in spring. Sequentially, BGS exhibited stronger positive correlation with autumn NPP in areas with less annual precipitation, which suggested the enhanced lagged suppressing effects of earlier spring phenology on ecosystem carbon assimilation during the later growing season under aggravated water stress. Overall, the strengthened NPP in spring was offset by its decrement in autumn, resulting in no obvious relationship between BGS and annual NPP (R = −0.34, p > 0.05) for the entire grasslands on the TP. The findings of this study imply that the lagged effects of phenology on the ecosystem productivity during the subsequent seasons should not be neglected in the future studies. Full article
(This article belongs to the Special Issue Remote Sensing of Climatic and Environmental Changes over the Antarctic, Arctic, and the Qinghai-Tibet Plateau)
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18 pages, 11466 KiB  
Article
Spatiotemporal Variability of Land Surface Albedo over the Tibet Plateau from 2001 to 2019
by Xingwen Lin, Jianguang Wen, Qinhuo Liu, Dongqin You, Shengbiao Wu, Dalei Hao, Qing Xiao, Zhaoyang Zhang and Zhenzhen Zhang
Remote Sens. 2020, 12(7), 1188; https://doi.org/10.3390/rs12071188 - 7 Apr 2020
Cited by 21 | Viewed by 4879
Abstract
As an essential climate variable (ECV), land surface albedo plays an important role in the Earth surface radiation budget and regional or global climate change. The Tibetan Plateau (TP) is a sensitive environment to climate change, and understanding its albedo seasonal and inter-annual [...] Read more.
As an essential climate variable (ECV), land surface albedo plays an important role in the Earth surface radiation budget and regional or global climate change. The Tibetan Plateau (TP) is a sensitive environment to climate change, and understanding its albedo seasonal and inter-annual variations is thus important to help capture the climate change rules. In this paper, we analyzed the large-scale spatial patterns, temporal trends, and seasonal variability of land surface albedo overall the TP, based on the moderate resolution imaging spectroradiometer (MODIS) MCD43 albedo products from 2001 to 2019. Specifically, we assessed the correlations between the albedo anomaly and the anomalies of normalized difference vegetation index (NDVI), the fraction of snow cover (snow cover), and land surface temperature (LST). The results show that there are larger albedo variations distributed in the mountainous terrain of the TP. Approximately 10.06% of the land surface is identified to have been influenced by the significant albedo variation from the year 2001 to 2019. The yearly averaged albedo was decreased significantly at a rate of 0.0007 (Sen’s slope) over the TP. Additionally, the yearly average snow cover was decreased at a rate of 0.0756. However, the yearly average NDVI and LST were increased with slopes of 0.0004 and 0.0253 over the TP, respectively. The relative radiative forcing (RRF) caused by the land cover change (LCC) is larger than that caused by gradual albedo variation in steady land cover types. Overall, the RRF due to gradual albedo variation varied from 0.0005 to 0.0170 W/m2, and the RRF due to LCC variation varied from 0.0037 to 0.0243 W/m2 during the years 2001 to 2019. The positive RRF caused by gradual albedo variation or the LCC can strengthen the warming effects in the TP. The impact of the gradual albedo variations occurring in the steady land cover types was very low between 2001 and 2019 because the time series was short, and it therefore cannot be neglected when examining radiative forcing for a long time series regarding climate change. Full article
(This article belongs to the Special Issue Remote Sensing of Climatic and Environmental Changes over the Antarctic, Arctic, and the Qinghai-Tibet Plateau)
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18 pages, 3591 KiB  
Article
Radar-Derived Internal Structure and Basal Roughness Characterization along a Traverse from Zhongshan Station to Dome A, East Antarctica
by Kun Luo, Sixin Liu, Jingxue Guo, Tiantian Wang, Lin Li, Xiangbin Cui, Bo Sun and Xueyuan Tang
Remote Sens. 2020, 12(7), 1079; https://doi.org/10.3390/rs12071079 - 27 Mar 2020
Cited by 9 | Viewed by 2707
Abstract
The internal layers of ice sheets from ice-penetrating radar (IPR) investigation preserve critical information about the ice-flow field and englacial conditions. This paper presents a new detailed analysis of spatial distribution characteristics of internal layers and subglacial topography of the East Antarctic ice [...] Read more.
The internal layers of ice sheets from ice-penetrating radar (IPR) investigation preserve critical information about the ice-flow field and englacial conditions. This paper presents a new detailed analysis of spatial distribution characteristics of internal layers and subglacial topography of the East Antarctic ice sheet (EAIS) from Zhongshan Station to Dome A. The radar data of 1244 km along a traverse between Zhongshan Station and Dome A of EAIS were collected during the 29th Chinese National Antarctic Research Expedition (CHINARE 29, 2012/2013). In this study, the Internal Layering Continuity Index (ILCI) and basal roughness were taken as indicators to provide an opportunity to evaluate the past internal environment and dynamics of the ice sheet. Except for the upstream of Lambert Glacier, the fold patterns of internal layers are basically similar to that of the bed topography. The relatively flat basal topography and the decrease of ILCI with increasing depth provide evidence for identifying previous rapid ice flow areas that are unavailable to satellites, especially in the upstream of Lambert Glacier. Continuous internal layers of Dome A, recording the spatial change of past ice accumulation and ice-flow history over 160 ka, almost extend to the bed, with high ILCI and high basal roughness of the corresponding bed topography. There are three kinds of basal roughness patterns along the traverse, that is, “low ξt low η”, “low ξt high η”, and “high ξt high η”, where ξt represents the amplitude of the undulations, and quantifies the vertical variation of the bedrock, and η measures the frequency variation of fluctuations and the horizontal irregularity of the profile. The characteristics of internal layers and basal topography of the traverse between Zhongshan Station and Dome A provide new information for understanding the ancient ice-flow activity and the historical evolution of EAIS. Full article
(This article belongs to the Special Issue Remote Sensing of Climatic and Environmental Changes over the Antarctic, Arctic, and the Qinghai-Tibet Plateau)
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21 pages, 8212 KiB  
Article
Trends in the Stability of Antarctic Coastal Polynyas and the Role of Topographic Forcing Factors
by Liyuan Jiang, Yong Ma, Fu Chen, Jianbo Liu, Wutao Yao, Yubao Qiu and Shuyan Zhang
Remote Sens. 2020, 12(6), 1043; https://doi.org/10.3390/rs12061043 - 24 Mar 2020
Cited by 4 | Viewed by 3221
Abstract
Polynyas are an important factor in the Antarctic and Arctic climate, and their changes are related to the ecosystems in the polar regions. The phenomenon of polynyas is influenced by the combination of inherent persistence and dynamic factors. The dynamics of polynyas are [...] Read more.
Polynyas are an important factor in the Antarctic and Arctic climate, and their changes are related to the ecosystems in the polar regions. The phenomenon of polynyas is influenced by the combination of inherent persistence and dynamic factors. The dynamics of polynyas are greatly affected by temporal dynamical factors, and it is difficult to objectively reflect the internal characteristics of their formation. Separating the two factors effectively is necessary in order to explore their essence. The Special Sensor Microwave/Imager (SSM/I) passive microwave sensor has been making observations of Antarctica for more than 20 years, but it is difficult for existing current sea ice concentration (SIC) products to objectively reflect how the inherent persistence factors affect the formation of polynyas. In this paper, we proposed a long-term multiple spatial smoothing method to remove the influence of dynamic factors and obtain stable annual SIC products. A halo located on the border of areas of low and high ice concentration around the Antarctic coast, which has a strong similarity with the local seabed in outline, was found using the spatially smoothed SIC products and seabed. The relationship of the polynya location to the wind and topography is a long-understood relationship; here, we quantify that where there is an abrupt slope and wind transitions, new polynyas are best generated. A combination of image expansion and threshold segmentation was used to extract the extent of sea ice and coastal polynyas. The adjusted record of changes in the extent of coastal polynyas and sea ice in the Southern Ocean indicate that there is a negative correlation between them. Full article
(This article belongs to the Special Issue Remote Sensing of Climatic and Environmental Changes over the Antarctic, Arctic, and the Qinghai-Tibet Plateau)
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19 pages, 6851 KiB  
Article
Estimation of Shortwave Solar Radiation on Clear-Sky Days for a Valley Glacier with Sentinel-2 Time Series
by Yanli Zhang, Xiang Qin, Xin Li, Jun Zhao and Yushuo Liu
Remote Sens. 2020, 12(6), 927; https://doi.org/10.3390/rs12060927 - 13 Mar 2020
Cited by 12 | Viewed by 3906
Abstract
Downward surface shortwave radiation (DSSR) is the main energy source for most glacial melting, and Moderate Resolution Imaging Spectroradiometer (MODIS) and Landsat Thematic Mapper (TM) data have been used extensively in the inversion of input parameters for estimating DSSR. However, for valley glaciers [...] Read more.
Downward surface shortwave radiation (DSSR) is the main energy source for most glacial melting, and Moderate Resolution Imaging Spectroradiometer (MODIS) and Landsat Thematic Mapper (TM) data have been used extensively in the inversion of input parameters for estimating DSSR. However, for valley glaciers under complex climatic conditions, the values of MODIS atmospheric products, especially aerosol products, are often invalid, and TM images are always saturated with snow. Furthermore, an estimation model based on optical satellite images must simultaneously consider terrain and atmospheric effects and the transient nature of ice/snow albedo. Based on a high-resolution (12 m) digital elevation model (DEM), the newly launched Sentinel-2 satellites, rather than MODIS and TM, were used to provide input data for our published mountain radiation scheme in a valley glacier. Considering Laohugou Glacier No. 12 as the study area, 62 typical Sentinel-2 scenes were selected and spatiotemporal DSSR variations on the glacier surface were obtained with a 10 m spatial resolution during a mass-balance year from September 2017 to August 2018. Ground-based measurements on 52 clear-sky days were used for validation and the mean bias error (MBE = −16.0 W/m2) and root-mean-square difference (RMSD = 73.6 W/m2) were relatively low. The results confirm that DSSR is affected mainly by the solar zenith angle and atmospheric attenuation in flat areas of valley glaciers, while in areas with complex terrain, the DSSR received by the glacier surface is affected primarily by the terrain and ice/snow albedo, which exhibits very high spatial heterogeneity. Full article
(This article belongs to the Special Issue Remote Sensing of Climatic and Environmental Changes over the Antarctic, Arctic, and the Qinghai-Tibet Plateau)
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21 pages, 8590 KiB  
Article
New Insights in Regional Climate Change: Coupled Land Albedo Change Estimation in Greenland from 1981 to 2017
by Fei Peng, Haoran Zhou, Gong Chen, Qi Li, Yongxing Wu and Heming Liang
Remote Sens. 2020, 12(5), 756; https://doi.org/10.3390/rs12050756 - 25 Feb 2020
Cited by 1 | Viewed by 3614
Abstract
Land albedo is an essential variable in land surface energy balance and climate change. Within regional land, albedo has been altered in Greenland as ice melts and runoff increases in response to global warming against the period of the pre-industrial revolution. The assessment [...] Read more.
Land albedo is an essential variable in land surface energy balance and climate change. Within regional land, albedo has been altered in Greenland as ice melts and runoff increases in response to global warming against the period of the pre-industrial revolution. The assessment of spatiotemporal variation in albedo is a prerequisite for accurate prediction of ice sheet loss and future climate change, as well as crucial prior knowledge for improving current climate models. In our study, we employed the satellite data product from the global land surface satellite (GLASS) project to obtain the spatiotemporal variation of albedo from 1981 to 2017 using the non-parameter-based M-K (Mann-Kendall) method. It was found that the albedo generally showed a decreasing trend in the past 37 years (−0.013 ± 0.001 decade−1, p < 0.01); in particular, the albedo showed a significant increasing trend in the middle part of the study area but a decreasing trend in the coastal area. The interannual and seasonal variations of albedo showed strong spatial-temporal heterogeneity. Additionally, based on natural and anthropogenic factors, in order to further reveal the potential effects of spatiotemporal variation of albedo on the regional climate, we coupled climate model data with observed data documented by satellite and adopted a conceptual experiment for detections and attributions analysis. Our results showed that both the greenhouse gas forcing and aerosol forcing induced by anthropogenic activities in the past 37 decades were likely to be the main contributors (46.1%) to the decrease of albedo in Greenland. Here, we indicated that overall, Greenland might exhibit a local warming effect based on our study. Albedo–ice melting feedback is strongly associated with local temperature changes in Greenland. Therefore, this study provides a potential pathway to understanding climate change on a regional scale based on the coupled dataset. Full article
(This article belongs to the Special Issue Remote Sensing of Climatic and Environmental Changes over the Antarctic, Arctic, and the Qinghai-Tibet Plateau)
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22 pages, 6313 KiB  
Article
Glacier Variations at Xinqingfeng and Malan Ice Caps in the Inner Tibetan Plateau Since 1970
by Zhen Zhang, Shiyin Liu, Zongli Jiang, Donghui Shangguan, Junfeng Wei, Wanqin Guo, Junli Xu, Yong Zhang, Shasha Zhang and Danni Huang
Remote Sens. 2020, 12(3), 421; https://doi.org/10.3390/rs12030421 - 28 Jan 2020
Cited by 9 | Viewed by 3000
Abstract
The inner Tibetan Plateau is a glacierized region where glaciers show heterogeneous change. The Xinqingfeng and Malan ice caps are located in this region, and a transition zone exists with shifting influences between the westerlies and Indian summer monsoon. However, there is a [...] Read more.
The inner Tibetan Plateau is a glacierized region where glaciers show heterogeneous change. The Xinqingfeng and Malan ice caps are located in this region, and a transition zone exists with shifting influences between the westerlies and Indian summer monsoon. However, there is a lack of detailed information regarding glacier area and mass changes in this region before 2000. In the present study, we describe an integrated view of the glacier area and its mass changes for Mt. Xinqingfeng and Mt. Malan as derived from topographic maps, Landsat, ASTER, SRTM DEM, and TerraSAR-X/TanDEM-X from 1970 to 2012 and from 1970 to 2018, respectively. Our results show that the glaciers experienced a slight shrinkage in area by 0.09 ± 0.03% a−1 from 1970 to 2018 with a median mass loss rate of 0.22 ± 0.17 m w.e. a−1 and 0.29 ± 0.17 m w.e. a−1 between 1999 and 2012 at Mt. Xinqingfeng and Mt. Malan, respectively. The glaciers of Mt. Malan had a total mass loss of 0.19 ± 0.14 m w.e. a−1 during the period 1970–1999. A minimum of seven glaciers at Mt. Xinqingfeng and Mt. Malan showed heterogeneous variations with either surging or advancing during the observation period. Among them, the West Monuomaha Glacier, Monuomaha Glacier, and Zu Glacier were identified as surging glaciers, and the others may also be surging glaciers, although more evidence is required. These glaciers showed a long active period and low velocities. Therefore, we suggested that thermal controls are important for surge initiation and recession. Full article
(This article belongs to the Special Issue Remote Sensing of Climatic and Environmental Changes over the Antarctic, Arctic, and the Qinghai-Tibet Plateau)
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20 pages, 3416 KiB  
Article
A Comprehensive Evaluation of 4-Parameter Diurnal Temperature Cycle Models with In Situ and MODIS LST over Alpine Meadows in the Tibetan Plateau
by Yaping Chang, Yongjian Ding, Qiudong Zhao and Shiqiang Zhang
Remote Sens. 2020, 12(1), 103; https://doi.org/10.3390/rs12010103 - 27 Dec 2019
Cited by 13 | Viewed by 2815
Abstract
Diurnal variation of land surface temperature (LST) is essential for land surface energy and water balance at regional or global scale. Diurnal temperature cycle (DTC) model with least parameters and high accuracy is the key issue in estimating the spatial–temporal variation of DTC. [...] Read more.
Diurnal variation of land surface temperature (LST) is essential for land surface energy and water balance at regional or global scale. Diurnal temperature cycle (DTC) model with least parameters and high accuracy is the key issue in estimating the spatial–temporal variation of DTC. The alpine meadow is the main land cover in the Tibetan Plateau (TP). However, few studies have been reported on the performance of different DTC models over alpine meadows in the TP. Four semi-empirical types of DTC models were used to generate nine 4-parameter (4-para) models by fixing some of free parameters. The performance of the nine 4-para DTC models were evaluated with four in situ and MODIS observations. All models except GOT09-dT-ts (dT means the temperature residual between T0 and T (t→∞); ts means the time when free attenuation begins) had higher correlation with in situ data (R2 > 0.9), while the INA08-ts model performed best with NSE of 0.99 and RMSE of 2.04 K at all sites. The GOT09-ts-τ (τ is the total optical thickness), VAN06-ts-ω1 (ω1 means the half-width of the cosine term in the morning), and GOT01-ts models had better performance, followed by GOT09-dT-τ, GOT01-dT, and VAN06-ts-ω2 (ω2 means the half-width of the cosine term in the afternoon) models. All models had higher accuracy in summer than in other seasons, while poorer performance was produced in winter. The INA08-ts model showed best performance among all seasons. Models with fixing ts could produce higher accuracy results than that with fixing dT. The comparison of INA08-ts model driven by in situ and Moderate Resolution Imaging Spectroradiometer (MODIS) data indicated that the simulation accuracy mainly depended on the accuracy of MODIS LST. The daily maximum temperature generated by the nine models had high accuracy when compared with in situ data. The sensitivity analysis indicated that the INA08-dT and GOT09-dT-ts models were more sensitive to parameter dT, while all models were insensitive to parameter ts, and all models had weak relationship with parameters ω and τ. This study provides a reference for exploring suitable DTC model in the TP. Full article
(This article belongs to the Special Issue Remote Sensing of Climatic and Environmental Changes over the Antarctic, Arctic, and the Qinghai-Tibet Plateau)
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20 pages, 18512 KiB  
Article
Evolving Instability of the Scar Inlet Ice Shelf based on Sequential Landsat Images Spanning 2005–2018
by Gang Qiao, Yanjun Li, Song Guo and Wenkai Ye
Remote Sens. 2020, 12(1), 36; https://doi.org/10.3390/rs12010036 - 20 Dec 2019
Cited by 11 | Viewed by 3428
Abstract
Following the large-scale disintegration of the Larsen B Ice Shelf (LBIS) in 2002, ice flow velocities for its remnants and tributary glaciers began to increase. In this study, we used sequential Landsat images spanning 2005–2018 to produce detailed maps of the ice flow [...] Read more.
Following the large-scale disintegration of the Larsen B Ice Shelf (LBIS) in 2002, ice flow velocities for its remnants and tributary glaciers began to increase. In this study, we used sequential Landsat images spanning 2005–2018 to produce detailed maps of the ice flow velocities and surface features for the Scar Inlet Ice Shelf (SIIS). Our results indicate that the ice flow velocities for the SIIS and its tributary glaciers (Flask and Leppard Glaciers) have substantially increased since 2005. Surface features, such as rifts and crevasses, have also substantially increased in both scope and scale and are particularly evident in the region between the Leppard Glacier and the Jason Peninsula. Several indicators—including the acceleration of ice flows, the rapid growth of major surface rifts, the heavily enhanced surface crevasses, and the dynamic position of the ice front—point to the evolving instability of the SIIS. These same indicators describe the conditions for the LBIS leading up to its 2002 collapse. To date, however, the SIIS remains intact. The formation of fast ice supporting the ice shelf front, combined with moderate mean summer temperatures, may be preventing or delaying its collapse. Full article
(This article belongs to the Special Issue Remote Sensing of Climatic and Environmental Changes over the Antarctic, Arctic, and the Qinghai-Tibet Plateau)
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17 pages, 16668 KiB  
Article
Evolution of Surge-Type Glaciers in the Yangtze River Headwater Using Multi-Source Remote Sensing Data
by Jin Yan, Mingyang Lv, Zhixing Ruan, Shiyong Yan and Guang Liu
Remote Sens. 2019, 11(24), 2991; https://doi.org/10.3390/rs11242991 - 12 Dec 2019
Cited by 7 | Viewed by 2470
Abstract
A surge-type glacier is a special and dangerous type of glacier, which can advance quickly in a short-time with cycles. Glaciers in the Yangtze River headwater are generally acknowledged to be in a stable state. However, not all of those glaciers are stable. [...] Read more.
A surge-type glacier is a special and dangerous type of glacier, which can advance quickly in a short-time with cycles. Glaciers in the Yangtze River headwater are generally acknowledged to be in a stable state. However, not all of those glaciers are stable. In this paper, five glaciers from the Yangtze River headwater glacier were selected as the experimental subjects, and multi-source remote sensing images were used to study and analyze the surge behavior over the past 30 years. Based on the Landsat series data, ERS-2, and ENVISAT radar data, this paper extracts the glacier centerline information, glacial area information, and glacial flow velocity during different time periods from 1988 to 2018, which are used to monitor the active periods of glacier surges. We found three surge-type glaciers in the study area. The glacial characteristics of the three glaciers showed some drastic changes, they can advance quickly nearly 800 m in active periods, their area change can reach 2.0 × 106 m2, and their flow velocity can suddenly increase by dozens of times. Surging periods and the initiated time of the three glaciers are different, which are locked in 1997, 2003, and 1997–1998. All those surges ended within one to two years. We suggest that the surges in this paper are dominated by hydrological conditions. Full article
(This article belongs to the Special Issue Remote Sensing of Climatic and Environmental Changes over the Antarctic, Arctic, and the Qinghai-Tibet Plateau)
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24 pages, 11225 KiB  
Article
Analysis of Long-Term Moon-Based Observation Characteristics for Arctic and Antarctic
by Yue Sui, Huadong Guo, Guang Liu and Yuanzhen Ren
Remote Sens. 2019, 11(23), 2805; https://doi.org/10.3390/rs11232805 - 27 Nov 2019
Cited by 18 | Viewed by 2702
Abstract
The Antarctic and Arctic have always been critical areas of earth science research and are sensitive to global climate change. Global climate change exhibits diversity characteristics on both temporal and spatial scales. Since the Moon-based earth observation platform could provide large-scale, multi-angle, and [...] Read more.
The Antarctic and Arctic have always been critical areas of earth science research and are sensitive to global climate change. Global climate change exhibits diversity characteristics on both temporal and spatial scales. Since the Moon-based earth observation platform could provide large-scale, multi-angle, and long-term measurements complementary to the satellite-based Earth observation data, it is necessary to study the observation characteristics of this new platform. With deepening understanding of Moon-based observations, we have seen its good observation ability in the middle and low latitudes of the Earth’s surface, but for polar regions, we need to further study the observation characteristics of this platform. Based on the above objectives, we used the Moon-based Earth observation geometric model to quantify the geometric relationship between the Sun, Moon, and Earth. Assuming the sensor is at the center of the nearside of the Moon, the coverage characteristics of the earth feature points are counted. The observation intervals, access frequency, and the angle information of each point during 100 years were obtained, and the variation rule was analyzed. The research showed that the lunar platform could carry out ideal observations for the polar regions. For the North and South poles, a continuous observation duration of 14.5 days could be obtained, and as the latitude decreased, the duration time was reduced to less than one day at the latitude of 65° in each hemisphere. The dominant observation time of the North Pole is concentrated from mid-March to mid-September, and for the South Pole, it is the rest of the year, and as the latitude decreases, it extends outward from both sides. The annual coverage time and frequency will change with the relationship between the Moon and the Earth. This study also proves that the Moon-based observation has multi-angle observation advantages for the Arctic and the Antarctic areas, which can help better understand large-scale geoscientific phenomena. The above findings indicate that the Moon-based observation can be applied as a new type of remote sensing technology to the observation field of the Earth’s polar regions. Full article
(This article belongs to the Special Issue Remote Sensing of Climatic and Environmental Changes over the Antarctic, Arctic, and the Qinghai-Tibet Plateau)
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23 pages, 4131 KiB  
Article
Greening Implication Inferred from Vegetation Dynamics Interacted with Climate Change and Human Activities over the Southeast Qinghai–Tibet Plateau
by Hao Li, Liu Liu, Xingcai Liu, Xiuping Li and Zongxue Xu
Remote Sens. 2019, 11(20), 2421; https://doi.org/10.3390/rs11202421 - 18 Oct 2019
Cited by 30 | Viewed by 4010
Abstract
Vegetation dynamics are sensitive to climate change and human activities, as vegetation interacts with the hydrosphere, atmosphere, and biosphere. The Yarlung Zangbo River (YZR) basin, with the vulnerable ecological environment, has experienced a series of natural disasters since the new millennium. Therefore, in [...] Read more.
Vegetation dynamics are sensitive to climate change and human activities, as vegetation interacts with the hydrosphere, atmosphere, and biosphere. The Yarlung Zangbo River (YZR) basin, with the vulnerable ecological environment, has experienced a series of natural disasters since the new millennium. Therefore, in this study, the vegetation dynamic variations and their associated responses to environmental changes in the YZR basin were investigated based on Normalized Difference Vegetation Index (NDVI) and Global Land Data Assimilation System (GLDAS) data from 2000 to 2016. Results showed that (1) the YZR basin showed an obvious vegetation greening process with a significant increase of the growing season NDVI (Zc = 2.31, p < 0.05), which was mainly attributed to the wide greening tendency of the downstream region that accounted for over 50% area of the YZR basin. (2) Regions with significant greening accounted for 25.4% of the basin and were mainly concentrated in the Nyang River and Parlung Tsangpo River sub-basins. On the contrary, the browning regions accounted for <25% of the basin and were mostly distributed in the urbanized cities of the midstream, implying a significant influence of human activities on vegetation greening. (3) The elevation dependency of the vegetation in the YZR basin was significant, showing that the vegetation of the low-altitude regions was better than that of the high-altitude regions. The greening rate exhibited a significantly more complicated relationship with the elevation, which increased with elevated altitude (above 3500 m) and decreased with elevated altitude (below 3500 m). (4) Significantly positive correlations between the growing season NDVI and surface air temperature were detected, which were mainly distributed in the snow-dominated sub-basins, indicating that glaciers and snow melting processes induced by global warming play an important role in vegetation growth. Although basin-wide non-significant negative correlations were found between precipitation and growing season NDVI, positive influences of precipitation on vegetation greening occurred in the arid and semi-arid upstream region. These findings could provide important information for ecological environment protection in the YZR basin and other high mountain regions. Full article
(This article belongs to the Special Issue Remote Sensing of Climatic and Environmental Changes over the Antarctic, Arctic, and the Qinghai-Tibet Plateau)
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19 pages, 3580 KiB  
Article
Automatically Extracted Antarctic Coastline Using Remotely-Sensed Data: An Update
by Yining Yu, Zhilun Zhang, Mohammed Shokr, Fengming Hui, Xiao Cheng, Zhaohui Chi, Petra Heil and Zhuoqi Chen
Remote Sens. 2019, 11(16), 1844; https://doi.org/10.3390/rs11161844 - 8 Aug 2019
Cited by 17 | Viewed by 5447
Abstract
The temporal and spatial variability of the Antarctic coastline is a clear indicator of change in extent and mass balance of ice sheets and shelves. In this study, the Canny edge detector was utilized to automatically extract high-resolution information of the Antarctic coastline [...] Read more.
The temporal and spatial variability of the Antarctic coastline is a clear indicator of change in extent and mass balance of ice sheets and shelves. In this study, the Canny edge detector was utilized to automatically extract high-resolution information of the Antarctic coastline for 2005, 2010, and 2017, based on optical and microwave satellite data. In order to improve the accuracy of the extracted coastlines, we developed the Canny algorithm by automatically calculating the local low and high thresholds via the intensity histogram of each image to derive thresholds to distinguish ice sheet from water. A visual comparison between extracted coastlines and mosaics from remote sensing images shows good agreement. In addition, comparing manually extracted coastline, based on prior knowledge, the accuracy of planimetric position of automated extraction is better than two pixels of Landsat images (30 m resolution). Our study shows that the percentage of deviation (<100 m) between automatically and manually extracted coastlines in nine areas around the Antarctica is 92.32%, and the mean deviation is 38.15 m. Our results reveal that the length of coastline around Antarctica increased from 35,114 km in 2005 to 35,281 km in 2010, and again to 35,672 km in 2017. Meanwhile, the total area of the Antarctica varied slightly from 1.3618 × 107 km2 (2005) to 1.3537 × 107 km2 (2010) and 1.3657 × 107 km2 (2017). We have found that the decline of the Antarctic area between 2005 and 2010 is related to the breakup of some individual ice shelves, mainly in the Antarctic Peninsula and off East Antarctica. We present a detailed analysis of the temporal and spatial change of coastline and area change for the six ice shelves that exhibited the largest change in the last decade. The largest area change (a loss of 4836 km2) occurred at the Wilkins Ice Shelf between 2005 and 2010. Full article
(This article belongs to the Special Issue Remote Sensing of Climatic and Environmental Changes over the Antarctic, Arctic, and the Qinghai-Tibet Plateau)
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13 pages, 4918 KiB  
Letter
Spatio-Temporal Analysis of Ice Sheet Snowmelt in Antarctica and Greenland Using Microwave Radiometer Data
by Lei Liang, Xinwu Li and Fei Zheng
Remote Sens. 2019, 11(16), 1838; https://doi.org/10.3390/rs11161838 - 7 Aug 2019
Cited by 18 | Viewed by 3525
Abstract
The surface snowmelt on ice sheets in polar areas (ice sheets of Greenland and Antarctica) is not only an important sensitive factor of global climate change, but also a key factor that controls the global climate. Spaceborne earth observation provides an efficient means [...] Read more.
The surface snowmelt on ice sheets in polar areas (ice sheets of Greenland and Antarctica) is not only an important sensitive factor of global climate change, but also a key factor that controls the global climate. Spaceborne earth observation provides an efficient means of measuring snowmelt dynamics. Based on an improved ice sheet snowmelt detection algorithm and several new proposed parameters for detecting change, polar ice sheet snowmelt dynamics were monitored and analyzed by using spaceborne microwave radiometer datasets from 1978 to 2014. Our results show that the change in intensity of Greenland and Antarctica snowmelt generally tended to increase and decrease, respectively. Moreover, we show that the de-trended snowmelt change in ice sheets of Greenland and Antarctica vary in anti-correlation patterns. Furthermore, analysis in Atlantic Multi-decadal Oscillation, North Atlantic Oscillation, and the Southern Annular Mode suggests that the Atlantic Ocean and atmosphere could be a possible link between the snowmelt variability of the ice sheets of Greenland and Antarctica. Full article
(This article belongs to the Special Issue Remote Sensing of Climatic and Environmental Changes over the Antarctic, Arctic, and the Qinghai-Tibet Plateau)
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17 pages, 2577 KiB  
Letter
Evaluation of Synoptic Snowfall on the Antarctic Ice Sheet Based on CloudSat, In-Situ Observations and Atmospheric Reanalysis Datasets
by Yihui Liu, Fei Li, Weifeng Hao, Jean-Pierre Barriot and Yetang Wang
Remote Sens. 2019, 11(14), 1686; https://doi.org/10.3390/rs11141686 - 16 Jul 2019
Cited by 13 | Viewed by 3711
Abstract
Snowfall data are vital in calculating the surface mass balance of the Antarctic Ice Sheet (AIS), where in-situ and satellite measurements are sparse at synoptic timescales. CloudSat data are used to construct Antarctic snowfall data at synoptic timescales to compensate for the sparseness [...] Read more.
Snowfall data are vital in calculating the surface mass balance of the Antarctic Ice Sheet (AIS), where in-situ and satellite measurements are sparse at synoptic timescales. CloudSat data are used to construct Antarctic snowfall data at synoptic timescales to compensate for the sparseness of synoptic snowfall data on the AIS and to better understand its surface mass balance. Synoptic CloudSat snowfall data are evaluated by comparison with daily snow accumulation measurements from ten automatic weather stations (AWSs) and the fifth generation of the European Centre for Medium-Range Weather Forecasts climate reanalysis (ERA5) snowfall. Synoptic snowfall data were constructed based on the CloudSat measurements within a radius of 1.41°. The results show that reconstructed CloudSat snowfall at daily and two-day resolutions cover about 28% and 29% of the area of the AIS, respectively. Daily CloudSat snowfall and AWS snow accumulation have similar trends at all stations. While influenced by stronger winds, >73.3% of extreme snow accumulation events correspond to snowfall at eight stations. Even if the CloudSat snowfall data have not been assimilated into the ERA5 dataset, the synoptic CloudSat snowfall data are almost identical to the daily ERA5 snowfall with only small biases (average root mean square error and mean absolute error < 3.9 mm/day). Agreement among the three datasets suggests that the CloudSat data can provide reliable synoptic snowfall data in most areas of the AIS. The ERA5 dataset captures a large number of extreme snowfall events at all AWSs, with capture rates varying from 56% to 88%. There are still high uncertainties in ERA5. Nevertheless, the result suggests that ERA5 can be used to represent actual snowfall events on the AIS at synoptic timescale. Full article
(This article belongs to the Special Issue Remote Sensing of Climatic and Environmental Changes over the Antarctic, Arctic, and the Qinghai-Tibet Plateau)
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