1,721,813 research outputs found
Present stability of the Larsen C ice shelf, Antarctic Peninsula
Get PDFWe modelled the flow of the Larsen C and northernmost Larsen D ice shelves, Antarctic
Peninsula, using a model of continuum mechanics of ice flow, and applied a fracture criterion to the
simulated velocities to investigate the ice shelf’s present-day stability. Constraints come from satellite
data and geophysical measurements from the 2008/09 austral summer. Ice-shelf thickness was derived
from BEDMAP and ICESat data, and the density–depth relationship was inferred from our in situ seismic
reflection data. We obtained excellent agreements between modelled and measured ice-flow velocities,
and inferred and observed distributions of rifts and crevasses. Residual discrepancies between regions of
predicted fracture and observed crevasses are concentrated in zones where we assume a significant
amount of marine ice and therefore altered mechanical properties in the ice column. This emphasizes
the importance of these zones and shows that more data are needed to understand their influence on
ice-shelf stability. Modelled flow velocities and the corresponding stress distribution indicate that the
Larsen C ice shelf is stable at the moment. However, weakening of the elongated marine ice zones could
lead to acceleration of the ice shelf due to decoupling from the slower parts in the northern inlets and
south of Kenyon Peninsula, leading to a velocity distribution similar to that in the Larsen B ice shelf prior
to its disintegration
Ice-Front Retreat Controls on Ocean Dynamics Under Larsen C Ice Shelf, Antarctica
No full textIceberg A-68 separated from the Larsen C Ice Shelf in July 2017 and the impact of this event on the local ocean circulation has yet to be assessed. Here, we conduct numerical simulations of ocean dynamics near and below the ice shelf pre- and post-calving. Results agree with in situ and remote observations of the area as they indicate that basal melt is primarily controlled by wintertime sea-ice formation, which in turn produces High Salinity Shelf Water (HSSW). After the calving event, we simulate a 50% increase in HSSW intrusion under the ice shelf, enhancing ocean heat delivery by 30%. This results in doubling of the melt rate under Gipps Ice Rise, suggesting a positive feedback for further retreat that could destabilize the Larsen C Ice Shelf. Assessing the impact of ice-front retreat on the heat delivery under the ice is crucial to better understand ice-shelf dynamics in a warming environment.Physical and Space GeodesyGeoscience and Remote Sensin
Summertime water masses off the northern Larsen C Ice Shelf, Antarctica
No full textWe report on oceanographic observations made at the northern end of Larsen C Ice Shelf in the western Weddell Sea. It appears that the Larsen C continental shelf is flushed not by High Salinity Shelf Water from the southern continental shelf, but by Modified Weddell Deep Water (MWDW) flowing across the shelf break. MWDW is observed at the ice front, having tracked west along the northward facing slopes of depressions that reach to the shelf break. Ice Shelf Water observed near the ice front is not, however, derived from MWDW directly, but from MWDW pre-conditioned by winter cooling and by salinification from sea ice production. If the ice shelf base generally is being melted only by pre-conditioned MWDW, then, contrary to recent suggestions, changes in the temperature of the deep Weddell Sea are unlikely to have a major impact on melt rates at the base of Larsen C Ice Shelf
Impacts of the Larsen-C Ice Shelf calving event
No full textA giant iceberg has calved off the Larsen-C Ice Shelf, the largest remaining ice shelf on the Antarctic Peninsula, reducing its total area by ~10%. Whilst calving events are a natural phenomenon and thus not necessarily indicative of changing environmental conditions, such events can impact ice-shelf stability
History of Larsen C Ice Shelf reconstructed from sub-ice shelf and offshore sediments
Get PDFBecause ice shelves respond to climatic forcing over a range of time scales, from years to millennia, an understanding of their long-term history is critically needed for predicting their future evolution. We present the first detailed reconstruction of the Larsen C Ice Shelf (LCIS), eastern Antarctic Peninsula (AP), based on data from sediment cores recovered from below and in front of the ice shelf. Sedimentologic and chronologic information reveals that the grounding line (GL) of an expanded AP ice sheet had started its retreat from the midshelf prior to 17.7 ± 0.53 calibrated (cal.) kyr B.P., with the calving line following ~6 k.y. later. The GL had reached the inner shelf as early as 9.83 ± 0.85 cal. kyr B.P. Since ca. 7.3 ka, the ice shelf has undergone two phases of retreat but without collapse, indicating that the climatic limit of LCIS stability was not breached during the Holocene. Future collapse of the LCIS would therefore confirm that the magnitudes of both ice loss along the eastern AP and underlying climatic forcing are unprecedented during the past 11.5 k.y
Summertime cloud phase strongly influences surface melting on the Larsen C ice shelf, Antarctica
Get PDFSurface melting on Antarctic Peninsula ice shelves can influence ice shelf mass balance, and consequently sea level rise. We show that summertime cloud phase on the Larsen C ice shelf on the Antarctic Peninsula strongly influences the amount of radiation received at the surface and can determine whether or not melting occurs. While previous work has separately evaluated cloud phase and the surface energy balance (SEB) during summertime over Larsen C, no previous studies have examined this relationship quantitatively. Furthermore, regional climate models frequently produce surface radiation biases related to cloud ice and liquid water content. This study uses a high‐resolution regional configuration of the UK Met Office Unified Model (MetUM) to assess the influence of cloud ice and liquid properties on the SEB, and consequently melting, over the Larsen C ice shelf. Results from a case study show that simulations producing a vertical cloud phase structure more comparable to aircraft observations exhibit smaller surface radiative biases. A configuration of the MetUM adapted to improve the simulation of cloud phase reproduces the observed surface melt most closely. During a five‐week simulation of summertime conditions, model melt biases are reduced to <2 W m−2: a four‐fold improvement on a previous study that used default MetUM settings. This demonstrates the importance of cloud phase in determining summertime melt rates on Larsen C
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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