Kang YangNanjing University | NJU · School of Geography and Ocean Science
Kang Yang
PhD
River remote sensing, Greenland hydrology, and Arctic
About
68
Publications
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Introduction
Additional affiliations
January 2015 - March 2017
July 2014 - December 2014
September 2011 - December 2012
Publications
Publications (68)
Significance
Meltwater runoff from the Greenland ice sheet is a key contributor to global sea level rise and is expected to increase in the future, but it has received little observational study. We used satellite and in situ technologies to assess surface drainage conditions on the southwestern ablation surface after an extreme 2012 melting event....
Supraglacial stream networks incise via thermal erosion of underlying ice, reflecting a balance between localized fluvial incision and dynamic topography from underlying ice flow. We analyze high-resolution digital elevation models of the ice surface and bedrock in the southwest Greenland Ice Sheet from 1000-1600 m elevation to quantify the importa...
Internally drained catchments (IDCs) are hydrologic units on the Greenland Ice Sheet (GrIS) surface that collect and drain meltwater through supraglacial stream/river networks to terminal moulins or lakes. Their areas and shapes constrain the volumes and locations of supraglacial meltwater penetration into the ice. We map IDCs of the southwest GrIS...
Significance
Meltwater runoff is an important hydrological process operating on the Greenland ice sheet surface that is rarely studied directly. By combining satellite and drone remote sensing with continuous field measurements of discharge in a large supraglacial river, we obtained 72 h of runoff observations suitable for comparison with climate m...
Each summer, large volumes of surface meltwater drain off the Greenland ice sheet (GrIS) surface through moulins to the bed, impacting subglacial hydrology and ice flow dynamics. Supraglacial surface routing delays may propagate to englacial and subglacial hydrologic systems, requiring accurate assessment to correctly estimate subglacial effective...
Supraglacial rivers and lakes are important for the routing and storage of surface meltwater during the summer melt season across the Greenland Ice Sheet (GrIS) but remain poorly mapped and quantified across the northern part of the ice sheet, which is rapidly losing mass. Here we produce, for the first time, a high-resolution record of the supragl...
Supraglacial rivers and lakes are important for the routing and storage of surface meltwater during the summer melt season across the Greenland Ice Sheet (GrIS), yet remain poorly mapped and quantified across the northern part of the ice sheet, which is rapidly losing mass. Here we produce, for the first time, a high-resolution record of the suprag...
The dynamic variation in the water surfaces of the river networks within the Qinghai-Tibet Plateau affects the water resource availability for downstream ecosystems and human activities. Small rivers (with a river width less than 30 m) are an important component of this network, but are difficult to map in the Qinghai-Tibet Plateau. Firstly, the wi...
Several 30-m high-resolution global water body datasets have been developed in recent years and raised prospects for studying small (<300 m wide) rivers. River mapping accuracy is a key factor in determining the applicability and usefulness of a certain water body dataset, and accuracy assessment commonly requires numerous water validation points....
The northwest Greenland Ice Sheet (NW GrIS) is rapidly losing mass, and its ablation zone has expanded over the past two decades. Numerous supraglacial streams flowing directly over the NW GrIS surface drain a large lobe of grounded ice at Inglefield Land, into the proglacial Minturn River and the Nares Strait. Owing to the absence of moulins and c...
Supraglacial stream/river catchments drain large volumes of surface meltwater off the southwestern Greenland Ice Sheet surface. Previous studies note a strong seasonal evolution of their drainage density (Dd), a classic measure of drainage efficiency defined as open channel length per unit catchment area, but a direct correlation between Dd and sur...
Fast ice flow and substantial surface runoff form distinct and extensive supraglacial rivers and lakes on the northeast Greenland Ice Sheet (GrIS). These supraglacial rivers and lakes play an important role in controlling surface meltwater routing and storage. However, the hydromorphology of these complex supraglacial features remains poorly quanti...
The Greenland Ice Sheet’s contribution to global sea-level rise is accelerating ¹ due to increased melting of its bare-ice ablation zone 2–6 , but there is growing evidence that climate models overestimate runoff from this critical area of the ice sheet 7–12 . Current climate models assume all bare ice runoff escapes to the ocean, unlike snow cover...
Recent work has identified complex perennial supraglacial stream and river networks in areas of the Greenland Ice Sheet (GrIS) ablation zone. Current surface mass balance (SMB) models appear to overestimate meltwater runoff in these networks compared to in-channel measurements of supraglacial discharge. Here, we constrain SMB models using the hills...
Recent work has identified complex perennial supraglacial stream and river networks in areas of the Greenland Ice Sheet (GrIS) ablation zone. Current surface mass balance (SMB) models appear to overestimate meltwater runoff in these networks compared to in-channel measurements of supraglacial discharge. Here, we constrain SMB models using the hills...
Small rivers (width <30 m) are crucial components of Arctic terrestrial river networks. Yet to date, spatial resolution limitations of commonly used satellite imagery have inhibited quantification of their hydrography. By merging newly available Sentinel-2 multispectral satellite imagery with 2-m ArcticDEM digital elevation data, we created a conti...
Supraglacial lakes and rivers dominate the storage and transport of meltwater on the southwest Greenland Ice Sheet (GrIS) surface. Despite functioning as interconnected hydrologic networks, supraglacial lakes and rivers are commonly studied as independent features, resulting in an incomplete understanding of their collective impact on meltwater sto...
Rivers are essential to human livelihoods and agricultural production, yet human usage and irrigation are jeopardizing river sustainability. It is thus crucial to investigate the fine-scaled spatiotemporal dynamics of anthropogenic pressures on rivers. Most research, however, is conducted at the grid-scale, which impedes detailed investigations. In...
Croplands are commonly mapped using time series of remotely sensed images. The dynamic time warping (DTW) algorithm is an effective method for realizing this. However, DTW algorithm faces the challenge of capturing complete and accurate representative cropland time series on a national scale, especially in Asian countries where climatic and topogra...
Recent work has identified complex perennial supraglacial stream/river networks in areas of the Greenland Ice Sheet (GrIS) ablation zone. Current surface mass balance (SMB) models appear to overestimate meltwater runoff in these networks compared to in-channel measurements of supraglacial discharge. Here, we constrain SMB models using the Hillslope...
The Devon Ice Cap (DIC) is one of the largest ice masses in the Canadian Arctic. Each summer, extensive supraglacial river networks develop on the DIC surface and route large volumes of meltwater from ice caps to the ocean. Mapping their extent and understanding their temporal evolution are important for validating runoff routing and melt volumes p...
The ice flow velocities of many outlet glaciers on the Greenland Ice Sheet (GrIS) have increased dramatically over the past two decades, leading to significant GrIS mass loss. It is challenging to match multitemporal synthetic aperture radar or optical images because the GrIS ice surface changes dramatically, particularly during melt seasons. There...
With current scientific models forecasting an ice-free Central Arctic Ocean (CAO) in summer by mid-century and potentially earlier, a direct shipping route via the North Pole connecting markets in Asia, North America, and Europe may soon open. The Transpolar Sea Route (TSR) would represent a third Arctic shipping route in addition to the Northern S...
Small rivers (<30 m) are significant components of terrestrial river networks and remote sensing is a necessary tool to study them at the global scale. However, current global hydrography data products generally include only rivers that are wider than 30 m, neglecting smaller waterways and thus limiting our understanding of surface water processes,...
Surface runoff constitutes a large percentage of Greenland Ice Sheet (GrIS) mass loss at present but is difficult to measure directly. This study provides a novel method to estimate surface runoff through remote sensing of supraglacial lake volumes. Because terminal, non-draining (consistently expanding during the melt season) lakes impound runoff...
Abstract. Each summer, large volumes of surface meltwater flow over the Greenland Ice Sheet (GrIS) surface and drain through moulins to the ice sheet bed, impacting subglacial hydrology and ice flow dynamics. Runoff modulations, or routing delays due to ice surface conditions, thus propagate to englacial and subglacial hydrologic systems, requiring...
不透水面是重要的地表覆盖类型,利用卫星遥感影像准确提取不透水面信息对于掌握地表覆盖变化具有重要意义。现有研究已提出了多种不透水面遥感信息提取指数,但目前尚缺乏对这些不透水面指数的系统对比分析。利用Landsat8 卫星遥感影像,测试了目前8 种主要不透水面指数的提取精度。结果表明,在现有不透水面指数中,垂直不透水层指数能够有效增强不透水面信息,不透水面提取精度最高( 89.6%) ,其次是比值居民地指数和生物物理组分指数( 87.5%和87.4%) ,城市指数与新建筑指数提取精度再次之( 82.9%和80.0%) ,归一化差值不透水面指数、归一化建筑指数和基于指数的建筑指数未能有效增强不透水面信息,提取精度较低( < 75.0%) 。此外,这8 种不透水面指数都未能有效解决不透水面与大片裸地...
As the world urbanizes and builds more infrastructure, the extraction of built-up areas using remote sensing is crucial for monitoring land cover changes and understanding urban environments. Previous studies have proposed a variety of methods for mapping regional and global built-up areas. However, most of these methods rely on manual selection of...
Supraglacial rivers set efficacy and time lags by which surface meltwater is routed to the englacial, subglacial, and proglacial portions of ice masses. However, these hydrologic features remain poorly studied mainly because they are too narrow (typically <30 m) to be reliably delineated in conventional moderate-resolution satellite images (e.g., 3...
Large volumes of surface meltwater are routed through supraglacial internally drained catchments (IDCs) on the Greenland Ice Sheet surface each summer. Because surface routing impacts the timing and discharge of meltwater entering the ice sheet through moulins, accurately modeling moulin hydrographs is crucial for correctly coupling surface energy...
China has experienced alarming drought events during recent decades. In this study, we investigated monthly drought severity related to the eastern Pacific cooling (EPC), eastern Pacific warming (EPW), and central Pacific warming (CPW), and analysed the differential influence of canonical ENSO (c‐ENSO) and El Niño Modoki (ENSO_M) events on monthly...
Ice surface topography controls the routing of surface meltwater generated in the ablation zones of glaciers and ice sheets. Meltwater routing is a direct source of ice mass loss as well as a primary influence on subglacial hydrology and basal sliding of the ice sheet. Although the processes that determine ice sheet topography at the largest scales...
Large volumes of surface meltwater are routed through supraglacial internally drained catchments (IDCs) on the Greenland Ice Sheet surface each summer. Because surface routing impacts the timing and discharge of meltwater entering the ice sheet through moulins, it is crucial for correctly coupling surface energy and mass balance models with subglac...
People are increasingly becoming accustomed to taking photos of everyday life in modern cities and uploading them on major photo-sharing social media sites. These sites contain numerous pictures, but some have incomplete or blurred location information. The geo-localization of crowd-sourced pictures enriches the information contained therein, and i...
Ice flow can transfer variations in basal topography and basal slipperiness to the ice surface. Recent developments in this theory have made it possible to conduct numerical experiments to predict mesoscale surface topographical undulations and surface relief on an ice sheet-scale. Focussing here on the contemporary Greenland Ice Sheet (GrIS), we d...
Ice surface topography controls the primary routing of surface meltwater on ablation zones of glaciers and ice sheets. Meltwater routing is important for understanding and predicting ice sheet evolution because surface melt can be both a direct source of ice mass loss and an influence on basal sliding and ice advection. Although controls on ice she...
We document the density and hydrologic properties of bare, ablating ice in a mid-elevation (1215 m a.s.l.) supraglacial internally drained catchment in the Kangerlussuaq sector of the western Greenland ice sheet. We find low-density (0.43–0.91 g cm-3, μ=0.69 g cm-3) ice to at least 1.1 m depth below the ice sheet surface. This near-surface, low-den...
We document the density and hydrologic properties of bare, ablating ice in a mid-elevation (1215 m a.s.l.) supraglacial internally drained catchment near Kangerlussuaq, southwest Greenland. We find water saturated, low-density (474–725 kg m−3, μ = 688 kg m−3) ice to at least 1.1 m depth below the ice sheet surface. This near surface, low-density ic...
Growing interest in supraglacial channels, coupled with the increasing availability of high-resolution remotely sensed imagery of glacier surfaces, motivates the development and testing of new approaches to delineating surface meltwater channels. We utilized a high-resolution (2 m) digital elevation model of parts of the western margin of the Green...
High-resolution satellite imagery raises new prospects for detailed study of the Greenland ice sheet (GrIS) surface processes and ice discharge. However, dramatic spatiotemporal variability of ice surface reflectance and features poses significant challenges for registration of satellite imagery. This study proposes a new feature-based registration...
Choice of watershed delineation technique is an important source of uncertainty for cryo-hydrologic studies of the Greenland Ice Sheet (GrIS), with different methods yielding different watersheds for a common pour point. First, this paper explores this uncertainty for the Akuliarusiarsuup Kuua River Northern Tributary, Western Greenland. Next, a st...
Supraglacial rivers on the Greenland Ice Sheet (GrIS) transport large volumes of surface meltwater toward the ocean, yet have received relatively little direct research. This study presents field observations of channel width, depth, velocity, and water surface slope for nine supraglacial channels on the south-western GrIS collected between July 23...
Extensive, complex supraglacial river networks form on the southwest Greenland ice sheet (GrIS) surface each melt season. These networks are the dominant pathways for surface meltwater transport on this part of the ice sheet, but their fluvial morphometry has received little study. This paper utilizes high-resolution (2 m) WorldView-1/2 images, dig...
Digital elevation models (DEMs) of ice surface topography are often used for hydrologic analysis of the Greenland Ice Sheet (GrIS), but their suitability for this purpose has received little quantitative assessment. We compare remotely sensed maps of supraglacial lakes, rivers, and moulins with their DEM-modeled counterparts, using two moderate-res...
The land cover change from cultivated land to construction land is a world issue since the urbanization process is extensively studied around the world. Chengdu, China, is a representative urbanization area, where cloud cover is very high most of the time, restricting the use of visible and near-infrared satellite data. Here, we present a novel fra...
Tidal creeks (TCs) are transitional waterways between terrestrial and marine environments. Extracting geometric information for tidal creek networks (TCN) geometry from remote sensing is essential to understanding their characteristics, formation, and evolution. Currently, the major obstacles to automated recognition using digital elevation models...
Detecting rivers from remotely sensed imagery is an initial yet important step in space-based river studies. This paper proposes an automatic approach to enhance and detect complete river networks. The main contribution of this work is the characterization of rivers according to their Gaussian-like cross-sections and longitudinal continuity. A Gabo...
This study proposes a multiscale grid method to detect and reconstruct building roofs from airborne LiDAR data. The method interpolates unorganized LiDAR point cloud into two sets of grids with different spatial scales. In the large-scale grid, building seed regions are obtained, including detection of initial building seed regions and refinement o...
Surface melt has great impacts on the Greenland Ice Sheet (GrIS) mass balance and thereby has become the focus of significant GrIS research in recent years. The production, transport, and release processes of surface meltwater are the keys to understanding the potential impacts of the GrIS surface melt. These hydrological processes can elucidate th...
Although the topography of tidal flats is important for understanding their evolution, the spatial and temporal sampling frequency of such data remains limited. The waterline method has the potential to retrieve past tidal flat topography by utilizing large archives of satellite images. This study performs a quantitative analysis of the relationshi...
Registration of Mars remote sensing images is vital to jointly exploit and integrate the data from various sensors and periods, which is difficult because the lack of textural information in Mars images. We proposed a RANSAC-based iterative method, under the crater constraint, for affine invariant feature matching. The novelty of this method is, in...
Supraglacial meltwater streams and lakes that form each summer across large expanses of the Greenland Ice Sheet (GrIS) ablation zone have global implications for sea level rise but remain one of the least studied hydrologic systems on Earth. Remote sensing of supraglacial streams is challenging owing to their narrow width (1-30 m) and proximity to...
An automatic algorithm for stationary oil platform detection from multitemporal synthetic aperture radar data is proposed. The proposed algorithm consists of the following two parts. (1) A two-parameter constant false-alarm rate (CFAR) algorithm is used to extract targets from the Environment Satellite (ENVISAT) advanced synthetic aperture radar (A...
Surface ablation has great impact on the Greenland Ice Sheet(GrIS)mass balance and becomes the focus of GrIS research in recent years. The production, transportation and release of meltwater are the keys to understand the potential impact of the GrIS surface ablation. These hydrological processes could illustrate the following problems:How much mel...
Spatial weights matrix is used to represent geographical feature similarity. In situ similarity is represented by different kinds of distance measurements based on Euclidean distance. This kind of similarity builds on spatial dependence but neglects spatial nonstationarity. Here geographical feature similarity is defined as attribute and spatial si...
Electromagnetic radiation fields are ubiquitous in modern society. It is well known that long-term exposure in strong fields can result in bad effects to health due to some unknown mechanism. There are extensive research activities, in this paper, we study the simulation technique for spatial distribution of electromagnetic field in three dimension...
This paper introduced fast marching and minimum path into road extraction from remotely sensed images and proposed a new road extraction method.The work builds on a novel variant of fast marching approach,named as multi-points fast marching.The underlying idea is to calculate minimum action map with multi-points propagating simultaneously.Efficacio...
This paper introduced fast marching and minimum path into road extraction from remotely sensed images and proposed a new road extraction method. The work builds on a novel variant of fast marching approach, named as multi-points fast marching. The underlying idea is to calculate minimum action map with multi-points propagating simultaneously. Effic...
Land use change is not only related to some natural, social and economic factors, but also influenced by land use structure, policies and value orientation, and the influence of driving factors are spatially unstable. To make the simulation of land use patterns more reasonable and accurate, CLUE-S model is applied and improved. The authors use GWR...
Properties and distribution of submarine surface sediments are fundamental characteristics to show the main sedimentary dynamic processes, as well as essential tools to classify sedimentary environment. Based on the two main functions of GIS, the spatial interpolation and the raster overlay(algebra algorithms), a method has been developed to genera...