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Elevation change of Antarctic ice shelves from 2011 to 2016 using CryoSat-2
Daehyeon Han1, Jungho Im1, Hyangsun Han2
1UNIST, Korea, Republic of (South Korea); 2Korea Polar Research Institute
The elevation change of ice shelves in Antarctic area is the one of the key factors to identify the current melting processes associated with ice thickness change and ice mass balance. The acceleration of ice elevation change is also crucial to understand the trend of thinning ice shelves. Cryosat-2 has provided the recent surface elevation data over the Antarctica with high spatial resolution since 2010. In this study, the elevation change and its acceleration of Ross, Filchner-Ronne, and Amery ice shelves in Antarctic are derived using CryoSat-2 SARIn L2 surface elevation data from 2011 to 2016. The mean ice elevation change between 2011 and 2016 was negative, indicating the declination of ice elevation. The acceleration of annual ice elevation change was derived by coupling the elevation changes for two years from 2011-2012 to 2015-2016, which showed the faster thinning trend of study area over the years. The results provide the ice elevation change and its acceleration patterns over three major ice shelves in recent years, producing high resolution (2.5 km) grids of mean elevation change and acceleration. This study suggests that the declination rate of the mean ice elevation became higher over the study area when compared with the previous studies using other satellite measurements such as ICESat.
Comparison of Cryosat-2 Altimeter Data with ICESat-2 Simulator (SIMPL) Data over Western Greenland Outlet Glaciers
Gavin Christopher Medley1,2, Ute Christina Herzfeld1,2,3, Thomas Trantow1,2, Stephen Palm4, Harding David5, Dabney Philip5
1Department of Applied Mathematics, University of Colorado Boulder, USA; 2Department of Electrical, Computer and Energy Engineering, University of Colorado Boulder, USA; 3Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado, USA; 4Science Systems Applications Inc., Lanham, Maryland, USA; 5NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
In altimetry, different instruments exhibit varying data characteristics and spatial resolutions. We aim to compare these aspects between CryoSat-2 data and data generated by a simulator instrument for NASA's Ice, Cloud and Land Elevation Satellite (ICESat-2). Recently, a new form of altimeter -- micropulse photon-counting LiDAR, has been developed in preparation for the ICESat-2 mission which will carry the Advanced Topographic Laser Altimeter System (ATLAS) aboard. Simulator instruments have been developed to facilitate algorithm development and to evaluate the instrument concept prior to launch (now planned for 2018). One such simulator instrument is the Slope Imaging Multi-polarization Photon-counting LiDAR (SIMPL). A primary objective for the ICESat-2 mission is the precise measurement of global land and sea ice elevation change so to create realistic simulated ATLAS data, a campaign was launched in 2015 to fly SIMPL over locations in western Greenland.
As a general objective, we set out to study elevation change using CryoSat-2 data alongside SIMPL data. We use the elevation estimate derived from SIMPL flight data via the Density Dimension Algorithm (DDA) to analyze elevation and elevation change signal from CryoSat-2 data over northwest Greenland outlet glaciers Sverdrup Gletsjer and Gieseckebraer. We examine complex surface topography over crevassed areas in outlet glaciers using the DDA to evaluate the SIMPL instrument and compare the elevation estimate to CryoSat-2 data. In particular, we attend to the differences in spatial resolution between CryoSat-2 and SIMPL to evaluate the potential precision of ATLAS for the ICESat-2 mission. In the interest of maximizing useful data, we present a cloud segmentation algorithm that allows utilization of SIMPL data in the presence of modest cloud cover to create a more thorough comparison. Lastly, we validate the SIMPL instrument data by creating a difference map from CryoSat-2 elevation estimates and by analysis of surface roughness with comparison LandSat 8 images.
Analysis of the Complete Bouguer Gravity Anomaly and the Parker–Oldenburg Inversion for the Three-Dimensional Moho depth Model in the Central Alborz Structural Zone, Northern Iran
Soran Parang1, Abdolreza Safari1, Mohammad Ali Sharifi1, Abbas Bahrodi2
1School of Surveying and Geospatial Engineering, College of Engineering, University Of Tehran, Tehran, Iran; 2School of Mining Engineering, College of Engineering, University of Tehran, Tehran, Iran
The separative boundary between crustal and mantle rocks is called the Moho discontinuity. This boundary explains massive variations in the velocity of seismic waves, chemical structure, and lithology. The Moho depth, the depth of the boundary, is used in the identification of the general structure of the Earth’s crust, geology and regional tectonics. The aim of this study is to develop a Moho depth model for the central part of the Alborz Mountains, which is located in northern Iran, parallel to the southern margin of the Caspian Sea, using the complete Bouguer gravity anomaly data and the Parker-Oldenburg approach, which is utilized to determine the geometry of the density interface from the gravity anomaly. The free-air gravity anomaly data calculated from the EGM2008 geopotential model and spherical harmonics, terrain correction and elevation data from ETOPO1 are deployed to compute the complete Bouguer gravity anomaly in the studied region. For the estimation of the Moho depth, the complete Bouguer anomaly data is used in the Parker-Oldenburg inversion algorithm. According to this algorithm, the depth of the Moho discontinuity can be obtained through an iterative inversion procedure and a series of Fourier transforms of the gravitational anomaly. The results show that the Moho depth is ∼46 km beneath the northern part of the Central Iranian Plateau, 53–56 km in the central part of the Alborz Mountains and ∼48 km in the Southern Caspian Basin.