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46 results on '"Jeong, Seongsu"'

1. Retreat of Humboldt Gletscher, North Greenland, Driven by Undercutting From a Warmer Ocean

Author

Rignot, Eric, An, Lu, Chauche, Nolwenn, Morlighem, Mathieu, Jeong, Seongsu, Wood, Michael, Mouginot, Jeremie, Willis, Josh K, Klaucke, Ingo, Weinrebe, Wilhelm, and Muenchow, Andreas

Subjects
Climate Action, bathymetry, glaciology, Greenland, mass balance, physical ocean, sea level, Meteorology & Atmospheric Sciences
Abstract

Humboldt Gletscher is a 100-km wide, slow-moving glacier in north Greenland which holds a 19-cm global sea level equivalent. Humboldt has been the fourth largest contributor to sea level rise since 1972 but the cause of its mass loss has not been elucidated. Multi-beam echo sounding data collected in 2019 indicate a seabed 200 m deeper than previously known. Conductivity temperature depth data reveal the presence of warm water of Atlantic origin at 0°C at the glacier front and a warming of the ocean waters by 0.9 ± 0.1°C since 1962. Using an ocean model, we reconstruct grounded ice undercutting by the ocean, combine it with calculated retreat caused by ice thinning to floatation, and are able to fully explain the observed retreat. Two thirds of the retreat are caused by undercutting of grounded ice, which is a physical process not included in most ice sheet models.

Published
2021

2. Automatic delineation of glacier grounding lines in differential interferometric synthetic-aperture radar data using deep learning.

Author

Mohajerani, Yara, Jeong, Seongsu, Scheuchl, Bernd, Velicogna, Isabella, Rignot, Eric, and Milillo, Pietro

Abstract

Delineating the grounding line of marine-terminating glaciers-where ice starts to become afloat in ocean waters-is crucial for measuring and understanding ice sheet mass balance, glacier dynamics, and their contributions to sea level rise. This task has been previously done using time-consuming, mostly-manual digitizations of differential interferometric synthetic-aperture radar interferograms by human experts. This approach is no longer viable with a fast-growing set of satellite observations and the need to establish time series over entire continents with quantified uncertainties. We present a fully-convolutional neural network with parallel atrous convolutional layers and asymmetric encoder/decoder components that automatically delineates grounding lines at a large scale, efficiently, and accompanied by uncertainty estimates. Our procedure detects grounding lines within 232 m in 100-m posting interferograms, which is comparable to the performance achieved by human experts. We also find value in the machine learning approach in situations that even challenge human experts. We use this approach to map the tidal-induced variability in grounding line position around Antarctica in 22,935 interferograms from year 2018. Along the Getz Ice Shelf, in West Antarctica, we demonstrate that grounding zones are one order magnitude (13.3 ± 3.9) wider than expected from hydrostatic equilibrium, which justifies the need to map grounding lines repeatedly and comprehensively to inform numerical models.

Published
2021

10. The glaciers climate change initiative: Methods for creating glacier area, elevation change and velocity products

Author

Paul, Frank, Bolch, Tobias, Kääb, Andreas, Nagler, Thomas, Nuth, Christopher, Scharrer, Killian, Shepherd, Andrew, Strozzi, Tazio, Ticconi, Francesca, Bhambri, Rakesh, Berthier, Etienne, Bevan, Suzanne, Gourmelen, Noel, Heid, Torborg, Jeong, Seongsu, Kunz, Matthias, Lauknes, Tom Rune, Luckman, Adrian, Merryman Boncori, John Peter, Moholdt, Geir, Muir, Alan, Neelmeijer, Julia, Rankl, Melanie, VanLooy, Jeffrey, and Van Niel, Thomas

Published
2015
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20. Author Correction: Dynamic ice loss from the Greenland Ice Sheet driven by sustained glacier retreat (Communications Earth & Environment, (2020), 1, 1, (1), 10.1038/s43247-020-0001-2)

Author

King, Michalea D., Howat, Ian M., Candela, Salvatore G., Noh, Myoung J., Jeong, Seongsu, Noël, Brice P.Y., van den Broeke, Michiel R., Wouters, Bert, Negrete, Adelaide, Sub Dynamics Meteorology, and Marine and Atmospheric Research

Subjects
Environmental Science(all), Earth and Planetary Sciences(all)
Abstract

The original version of this Article contained an error in the spelling of the author Seongsu Jeong, which was incorrectly given as Seonsgu Jeong. This has now been corrected in both the PDF and HTML versions of the Article.

Published
2020

22. Dynamic ice loss from the Greenland Ice Sheet driven by sustained glacier retreat

Author

Sub Dynamics Meteorology, Marine and Atmospheric Research, King, Michalea D., Howat, Ian M., Candela, Salvatore G., Noh, Myoung J., Jeong, Seongsu, Noël, Brice P. Y., van den Broeke, Michiel R., Wouters, Bert, Negrete, Adelaide, Sub Dynamics Meteorology, Marine and Atmospheric Research, King, Michalea D., Howat, Ian M., Candela, Salvatore G., Noh, Myoung J., Jeong, Seongsu, Noël, Brice P. Y., van den Broeke, Michiel R., Wouters, Bert, and Negrete, Adelaide

Published
2020

23. Dynamic ice loss from the Greenland Ice Sheet driven by sustained glacier retreat

Author

King, Michalea D. (author), Howat, Ian M. (author), Candela, Salvatore G. (author), Noh, Myoung J. (author), Jeong, Seongsu (author), Noël, Brice P. Y. (author), van den Broeke, Michiel R. (author), Wouters, B. (author), Negrete, Adelaide (author), King, Michalea D. (author), Howat, Ian M. (author), Candela, Salvatore G. (author), Noh, Myoung J. (author), Jeong, Seongsu (author), Noël, Brice P. Y. (author), van den Broeke, Michiel R. (author), Wouters, B. (author), and Negrete, Adelaide (author)

Abstract

The Greenland Ice Sheet is losing mass at accelerated rates in the 21st century, making it the largest single contributor to rising sea levels. Faster flow of outlet glaciers has substantially contributed to this loss, with the cause of speedup, and potential for future change, uncertain. Here we combine more than three decades of remotely sensed observational products of outlet glacier velocity, elevation, and front position changes over the full ice sheet. We compare decadal variability in discharge and calving front position and find that increased glacier discharge was due almost entirely to the retreat of glacier fronts, rather than inland ice sheet processes, with a remarkably consistent speedup of 4–5% per km of retreat across the ice sheet. We show that widespread retreat between 2000 and 2005 resulted in a step-increase in discharge and a switch to a new dynamic state of sustained mass loss that would persist even under a decline in surface melt., Physical and Space Geodesy

Published
2020
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24. Author Correction: Dynamic ice loss from the Greenland Ice Sheet driven by sustained glacier retreat (Communications Earth & Environment, (2020), 1, 1, (1), 10.1038/s43247-020-0001-2)

Author

Sub Dynamics Meteorology, Marine and Atmospheric Research, King, Michalea D., Howat, Ian M., Candela, Salvatore G., Noh, Myoung J., Jeong, Seongsu, Noël, Brice P.Y., van den Broeke, Michiel R., Wouters, Bert, Negrete, Adelaide, Sub Dynamics Meteorology, Marine and Atmospheric Research, King, Michalea D., Howat, Ian M., Candela, Salvatore G., Noh, Myoung J., Jeong, Seongsu, Noël, Brice P.Y., van den Broeke, Michiel R., Wouters, Bert, and Negrete, Adelaide

Published
2020

30. Seasonal to decadal variability in ice discharge from the Greenland Ice Sheet

Author

King, Michalea D., Howat, Ian M., Jeong, Seongsu, Noh, Myoung J., Wouters, Bert, Noel, Brice, van den Broeke, Michiel R., King, Michalea D., Howat, Ian M., Jeong, Seongsu, Noh, Myoung J., Wouters, Bert, Noel, Brice, and van den Broeke, Michiel R.

Abstract

Rapid changes in thickness and velocity have been observed at many marine-terminating glaciers in Greenland, impacting the volume of ice they export, or discharge, from the ice sheet. While annual estimates of ice-sheet-wide discharge have been previously derived, higher-resolution records are required to fully constrain the temporal response of these glaciers to various climatic and mechanical drivers that vary in sub-annual scales. Here we sample outlet glaciers wider than 1 km (N=230) to derive the first continuous, ice-sheet-wide record of total ice sheet discharge for the 2000–2016 period, resolving a seasonal variability of 6 %. The amplitude of seasonality varies spatially across the ice sheet from 5 % in the southeastern region to 9 % in the northwest region. We analyze seasonal to annual variability in the discharge time series with respect to both modeled meltwater runoff, obtained from RACMO2.3p2, and glacier front position changes over the same period. We find that year-to-year changes in total ice sheet discharge are related to annual front changes (r2=0.59, p=10−4) and that the annual magnitude of discharge is closely related to cumulative front position changes (r2=0.79), which show a net retreat of >400 km, or an average retreat of >2 km, at each surveyed glacier. Neither maximum seasonal runoff or annual runoff totals are correlated to annual discharge, which suggests that larger annual quantities of runoff do not relate to increased annual discharge. Discharge and runoff, however, follow similar patterns of seasonal variability with near-coincident periods of acceleration and seasonal maxima. These results suggest that changes in glacier front position drive secular trends in discharge, whereas the impact of runoff is likely limited to the summer months when observed seasonal variations are substantially controlled by the timing of meltwater input.

Published
2018

31. Seasonal to decadal variability in ice discharge from the Greenland Ice Sheet

Author

Sub Dynamics Meteorology, Marine and Atmospheric Research, King, Michalea D., Howat, Ian M., Jeong, Seongsu, Noh, Myoung J., Wouters, Bert, Noel, Brice, van den Broeke, Michiel R., Sub Dynamics Meteorology, Marine and Atmospheric Research, King, Michalea D., Howat, Ian M., Jeong, Seongsu, Noh, Myoung J., Wouters, Bert, Noel, Brice, and van den Broeke, Michiel R.

Published
2018

38. Ubiquitous magneto-mechano-electric generator

Author

Ryu, Jungho, primary, Kang, Ju-Eun, additional, Zhou, Yuan, additional, Choi, Si-Young, additional, Yoon, Woon-Ha, additional, Park, Dong-Soo, additional, Choi, Jong-Jin, additional, Hahn, Byung-Dong, additional, Ahn, Cheol-Woo, additional, Kim, Jong-Woo, additional, Kim, Yang-Do, additional, Priya, Shashank, additional, Lee, Seung Yong, additional, Jeong, Seongsu, additional, and Jeong, Dae-Yong, additional

Published
2015
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46. Time Series Reconstruction of Surface Flow Velocity on Marine-terminating Outlet Glaciers

Author

Jeong, Seongsu

Subjects
Climate Change, Earth, Geography, Remote Sensing, glaciology, remote sensing, Greenland, Antarctica, glacier flow, Landsat
Abstract

The flow velocity of glacier and its fluctuation are valuable data to study the contribution of sea level rise of ice sheet by understanding its dynamic structure. Repeat-image feature tracking (RIFT) is a platform-independent, feature tracking-based velocity measurement methodology effective for building a time series of velocity maps from optical images. However, limited availability of perfectly-conditioned images motivated to improve robustness of the algorithm. With this background, we developed an improved RIFT algorithm based on multiple-image multiple-chip algorithm presented in Ahn and Howat (2011). The test results affirm improvement in the new RIFT algorithm in avoiding outlier, and the analysis of the multiple matching results clarified that each individual matching results worked in complementary manner to deduce the correct displacements.LANDSAT 8 is a new satellite in LANDSAT program that has begun its operation since 2013. The improved radiometric performance of OLI aboard the satellite is expected to enable better velocity mapping results than ETM+ aboard LANDSAT 7. However, it was not yet well studied that in what cases the new will sensor will be beneficial, and how much the improvement will be obtained. We carried out a simulation-based comparison between ETM+ and OLI and confirmed OLI outperforms ETM+ especially in low contrast conditions, especially in polar night, translucent cloud covers, and bright upglacier with less texture.We have identified a rift on ice shelf of Pine island glacier located in western Antarctic ice sheet. Unlike the previous events, the evolution of the current started from the center of the ice shelf. In order to analyze this unique event, we utilized the improved RIFT algorithm to its OLI images to retrieve time series of velocity maps. We discovered from the analyses that the part of ice shelf below the rift is changing its speed, and shifting of splashing crevasses on shear margin is migrating to the center of the shelf. Concerning the concurrent disintegration of ice melange on its western part of the terminus, we postulate that change in flow regime attributes to loss of resistance force exerted by the melange.There are several topics that need to be addressed for further improve the RIFT algorithm. As coregistration error is significant contributor to the velocity measurement, a method to mitigate that error needs to be devised. Also, considering that the domain of RIFT product spans not only in space but also in time, its regridding and gap filling work will benefit from extending its domain to both space and time.

Published
2015

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