![]() This style of calving, although less common at the time, also occurred prior to the break-up of the floating tongue ( Reference EpprechtEpprecht, 1987). Because these icebergs capsize, they release tremendous amounts of gravitational potential energy into the fjord (~10 14 J Amundson and others, 2008 Reference MacAyeal, Abbot and SergienkoMacAyeal and others, 2011). Tabular icebergs are now rare, with the dominant style of calving consisting of the detachment and immediate capsize of full-glacier-thickness icebergs (with volumes 0.1–0.25 km 3). Prior to and during the break-up of the floating tongue, the glacier frequently calved tabular icebergs with horizontal dimensions of 2–3 km ( Reference StoveStove and others, 1983 Reference Birnie and WilliamsBirnie and Williams, 1985). In the late 1990s the glacier began a rapid calving retreat ( Reference Thomas, Abdalati, Frederick, Krabill, Manizade and SteffenThomas and others, 2003 Reference Joughin, Abdalati and FahnestockJoughin and others, 2004 Reference Luckman and MurrayLuckman and Murray, 2005) that resulted in the loss of an extensive floating tongue ( Reference Csatho, Schenk, Van der Veen and KrabillCsatho and others, 2008). The glacier discharges into 55 km long Ilulissat Icefjord, which connects to Disko Bay by the town of Ilulissat. 1), a fast-flowing outlet glacier that drains >5% of the Greenland ice sheet ( Reference Rignot and KanagaratnamRignot and Kanagaratnam, 2006). We focus our study on Jakobshavn Isbræ, Greenland ( Fig. Here we show that by responding to induced ground tilt, coastal broadband seismometers can be used to detect and investigate much longer-period ( >100 s) calving-generated waves. Such measurements, although highly useful for understanding the oceanic response to calving events, are not possible in regions that do not have large ice shelves (e.g.most of Greenland). Previous work by Reference MacAyeal, Okal, Aster and BassisMacAyeal and others (2009) demonstrated that short-period (~10–50 s) calving-generated ocean waves can be recorded with seismometers deployed on ice shelves and tabular icebergs (which respond to ocean swell). However, difficulties in instrumenting proglacial fjords with pressure gauges have hampered efforts to quantitatively describe and assess the importance of calving-generated waves. Additionally, measurements of wave energy can be used to monitor calving ( Reference NettlesNettles and others, 2008) and to aid studies of iceberg-calving energetics and its consequences, such as turbulence generated in the wake of capsizing icebergs ( Reference BurtonBurton and others, 2012). These waves may (1) promote subsequent calving by causing ice fatigue through repeated flexure ( Reference MacAyeal, Okal, Aster and BassisMacAyeal and others, 2009), (2) agitate and fragment icebergs and sea ice, leading to a weakening of proglacial ice coverage ( Reference Amundson, Fahnestock, Truffer, Brown, Lüthi and MotykaAmundson and others, 2010), and (3) generate turbulence when breaking on shallow, sloping shorelines. Calving icebergs generate large, locally destructive ocean waves.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |