https://repository.kopri.re.kr/handle/201206/5469 2026-04-17T18:43:31Z 2026-04-17T18:43:31Z Christine F. Dow Christopher J. Zappa Duncan A. Young Alexander L. Forrest Kristin Poinar Donald D. Blankenship Chad A. Greene Jamin S. Greenbaum Lee, Won Sang https://repository.kopri.re.kr/handle/201206/9464 2022-03-24T07:12:12Z 2018-06-13T00:00:00Z

Title: Basal channels drive active surface hydrology and transverse ice shelf fracture Authors: Christine F. Dow; Christopher J. Zappa; Duncan A. Young; Alexander L. Forrest; Kristin Poinar; Donald D. Blankenship; Chad A. Greene; Jamin S. Greenbaum; Lee, Won Sang Abstract: Ice shelves control sea-level rise through frictional resistance, which slows the seaward flow of grounded glacial ice. Evidence from around Antarctica indicates that ice shelves are thinning and weakening, primarily driven by warm ocean water entering into the shelf cavities. We have identified a mechanism for ice shelf destabilization where basal channels underneath the shelves cause ice thinning that drives fracture perpendicular to flow. These channels also result in ice surface deformation, which diverts supraglacial rivers into the transverse fractures. We report direct evidence that a major 2016 calving event at Nansen Ice Shelf in the Ross Sea was the result of fracture driven by such channelized thinning and demonstrate that similar basal channel-driven transverse fractures occur elsewhere in Greenland and Antarctica. In the event of increased basal and surface melt resulting from rising ocean and air temperatures, ice shelves will become increasingly vulnerable to these tandem effects of basal channel destabilization.

2018-06-13T00:00:00Z Jordan H. Graw Park, Yongcheol Akram Mostafanejad Brian A. Young Charles A. Langston Samantha E. Hansen https://repository.kopri.re.kr/handle/201206/6491 2022-03-24T07:13:57Z 2017-01-01T00:00:00Z

Title: An Assessment of Crustal and Upper­Mantle Velocity Structure by Removing the Effect of an Ice Layer on the P­Wave Response: An Application to Antarctic Seismic Studies Authors: Jordan H. Graw; Park, Yongcheol; Akram Mostafanejad; Brian A. Young; Charles A. Langston; Samantha E. Hansen Abstract: Standard P-wave receiver function analyses in polar environments can be difficult because reverberations in thick ice coverage often mask important P-to-S con- versions from deeper subsurface structure and increase ambient noise levels, thereby significantly decreasing the signal-to-noise ratio of the data. In this study, we present an alternative approach to image the subsurface structure beneath ice sheets. We utilize downward continuation and wavefield decomposition of the P-wave response to obtain the up- and downgoing P and S wavefield potentials, which removes the effects of the ice sheet. The upgoing P wavefield, computed from decomposition of the waveform at a reference depth, is capable of indicating ice layer thickness. This simple step removes the necessity of modeling ice layer effects during iterative inversions and hastens the overall velocity analysis needed for downward continuation. The upgoing S wave is employed and modeled using standard inversion techniques as is done with receiver functions at the free surface using a least-squares approximation. To illustrate our proof of concept, data from several Antarctic networks are examined, and our results are com- pared with those from previous investigations using P- and S-wave receiver functions as well as body- and surface-wave tomographic analyses. We demonstrate how our ap- proach satisfactorily removes the ice layer, thus creating a dataset that can be modeled for crustal and upper-mantle structure. Solution models indicate crustal thicknesses as well as average crustal and upper-mantle shear-wave velocities.

2017-01-01T00:00:00Z Lee, Won Sang Lee, Jeonghoon Jung, Hyejung Hur, Soon Do Han, Yeongcheol Ham, Ji-Young https://repository.kopri.re.kr/handle/201206/6484 2022-03-24T07:13:59Z 2017-01-01T00:00:00Z

Title: A study on isotopic exchange between ice and meltwater using a melting experiment and 1-D model Authors: Lee, Won Sang; Lee, Jeonghoon; Jung, Hyejung; Hur, Soon Do; Han, Yeongcheol; Ham, Ji-Young Abstract: 얼음 동위원소의 시간적 변화를 규명하기 위하여 얼음 용융실험을 수행하였다. 적외선램프(75 W)를 이용하여 얼음과 램프사이의 거리를 일정하게 유지하면서 2 kg의 얼음을 13시간 동안 녹이면서 배출속도(1.96 ± 0.4cm/hr)를 최대한 일정하게 유지하였다. 증발 또는 승화로 인한 질량 감소는 거의 없었으므로(회수율 98.8%),얼음의 동위원소변화는 고체상인 얼음과 액체상인 얼음이 녹은 물의 동위원소교환반응에 의해 설명할 수 있다.얼음의 동위원소변화를 조절하는 것은 얼음이 동위원소교환반응에 얼마만큼 참여하는 가(？)와 동위원소교환상수(？？ )에 의해 결정되며 이를 결정하기 위하여 Lee et al. (2010a)에서 사용된 모델을 적용하였다. 얼음이 녹은 물의 산소와 수소의 안정동위원소의 선형관계는 기울기가 6.64로 계산되었으며, 이는 승화에 의한 동위원소 변동은 무시할 수 있으며, 주로 얼음과 물의 동위원소교환반응으로 설명할 수 있다. 모델과 실험결과를 비교하여 산소와 수소동위원소의 ？ 값은 각각 0.28, 0.20이었으며, ？？ 값은 각각 0.30, 0.41 hr-1로 계산되었다. 이는 통계적으로 유의미하게 다르다고 할 수 없으므로 향후 추가적인 실험이 요구된다.

2017-01-01T00:00:00Z Robin E. Bell Lee, Won Sang Alexandra Boghosian Massimo Frezzotti Christopher J. Zappa Kirsty J. Tinto Marco Tedesco Indrani Das Jonathan Kingslake Winnie Chu https://repository.kopri.re.kr/handle/201206/6007 2022-03-24T07:11:22Z 2017-01-01T00:00:00Z

Title: Antarctic ice shelf potentially stabilized by exportof meltwater in surface river Authors: Robin E. Bell; Lee, Won Sang; Alexandra Boghosian; Massimo Frezzotti; Christopher J. Zappa; Kirsty J. Tinto; Marco Tedesco; Indrani Das; Jonathan Kingslake; Winnie Chu Abstract: Meltwater stored in ponds1 and crevasses can weaken and fracture ice shelves, triggering their rapid disintegration2. This ice-shelf collapse results in an increased flux of ice from adjacent glaciers3 and ice streams, thereby raising sea level globally4. However, surface rivers forming on ice shelves could potentially export stored meltwater and prevent its destructive effects. Here we present evidence for persistent active drainage networks―interconnected streams, ponds and rivers―on the Nansen Ice Shelf in Antarctica. That export a large fraction of the ice shelf's meltwater into the ocean. We find that active drainage has exported water off the ice surface through waterfalls and dolines for more than a century. The surface river terminates in a 130-metre-wide waterfall that can export the entire annual surface melt over the course of seven days. During warmer melt seasons, these drainage networks adapt to changing environmental conditions by remaining active for longer and exporting more water. Similar networks are present on the ice shelf in front of Petermann Glacier, Greenland, but other systems, such as on the Larsen C and Amery Ice Shelves, retain surface water at present. The underlying reasons for export versus retention remain unclear. Nonetheless our results suggest that, in a future warming climate, surface rivers could export melt off the large ice shelves surrounding Antarctica―contrary to present Antarctic ice-sheet models1, which assume that meltwater is stored on the ice surface where it triggers ice-shelf disintegration. Ponded meltwater on the Larsen B Ice Shelf

2017-01-01T00:00:00Z