Tabular iceberg collisions within the coastal regime

MacAyeal, Douglas R.; Okal, Marianne; Thom, Jonathan E.; Brunt, Kelly M.; Kim, Young‐Jin; Bliss, Andrew

doi:10.3189/002214308784886180

Cited by 55 publications

(69 citation statements)

References 40 publications

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“…The role played by large tabular icebergs grounded by Ross Island during the study period has been well documented [ Robinson and Williams , ; MacAyeal et al ., ; Remy et al ., ; Brunt et al ., ]. Generally, sea ice breakout conditions in McMurdo Sound are driven by the gradual decay of the fast ice integrity over spring with the eventual complete breakout of sea ice from the McMurdo Ice Shelf front forced by storm activity in late summer.…”

Section: Discussionmentioning

confidence: 99%

“…Prior to the study period, the last time at which open water was abutting the ice shelf was 1998. The passage of large tabular icebergs B‐15A, B15‐K, and C16 (Figure ), which were grounded near Ross Island and restricted the local ocean circulation from mid‐2002 to mid‐2005 [ MacAyeal et al ., ; Robinson and Williams , ] played a role in the observed sea ice conditions during the study period [ Remy et al ., ]. Brunt et al .…”

Section: Sea Ice Types In the Study Areamentioning

confidence: 99%

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Sea ice freeboard in McMurdo Sound, Antarctica, derived by surface-validated ICESat laser altimeter data

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Haas

et al. 2013

J. Geophys. Res. Oceans

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Method-1 (M-1) follows those previously presented in the literature using the lowest elevations to construct an estimate of sea surface height. However, the lack of leads in the study area motivated the development of Method-2 (M-2) which utilizes tide models. Each year is divided into two investigation periods from September to December and February to June, and these investigations were further segmented by sea ice type, first-year (FY), and multiyear (MY). Both applied methods reveal a statistically significant linear increase in multiyear sea ice freeboard. For M-1, the mean freeboard increased over the study period from 0.53 to 1.00 m and for M-2 from 0.46 to 0.95 m. Evidence is presented that the multiyear sea ice freeboard increase is strongly linked to the development and incorporation of a subice platelet layer. No statistically significant trends were observed for first-year sea ice. ICESat derived freeboards over first-year and multiyear sea ice areas compare within one standard deviation of airborne measured freeboard in November 2009.

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Section: Discussionmentioning

confidence: 99%

Section: Sea Ice Types In the Study Areamentioning

confidence: 99%

Sea ice freeboard in McMurdo Sound, Antarctica, derived by surface-validated ICESat laser altimeter data

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Rack

Haas

et al. 2013

J. Geophys. Res. Oceans

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“…Examination of the drift trajectory of B15A [ MacAyeal et al , 2008] during the two IHT episodes illustrated in Figure 2, reveals that the origin of the seismic signals described above lies with the strike‐slip motion along a fault that is formed by the edge‐on‐edge contact between icebergs B15A and C16. Iceberg C16 was motionless throughout the period of observation because it was firmly grounded on the seabed.…”

Section: Seismogram Analysismentioning

confidence: 99%

“…In an effort to determine the source mechanism(s), we deployed a 4 station seismographic network during the Austral summer of 2003 on iceberg C16, a giant 50 km by 25 km tabular iceberg aground in the southwest Ross Sea, Antarctica (Figure 1). This iceberg was chosen because of its close proximity to B15A, a 150 by 50 km fragment of the iceberg B15 that was previously determined to radiate IHT [ Talandier et al , 2002], because it was routinely being struck by B15A because of the tidal drift of B15A (C16 was aground, and thus not drifting) [ MacAyeal et al , 2008], and because IHT was recorded during the previous 24 months on neighboring Ross Island by seismometers of the Mount Erebus Volcano Observatory [ Aster et al , 2004].…”

Section: Introductionmentioning

confidence: 99%

Seismic and hydroacoustic tremor generated by colliding icebergs

et al. 2008

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Iceberg harmonic tremor (IHT) emanating from tabular icebergs in the Southern Ocean and along calving margins of the Antarctic Ice Sheet is a complex, evolving signal at frequencies above approximately 0.5 Hz. IHT has been observed as T phases on islands in the equatorial Pacific, as hydroacoustic signals in the Indian Ocean, and by local and regional Antarctic seismic networks. To identify the IHT source mechanism and to understand its relevance to iceberg calving, evolution, and breakup, we deployed seismometers on a giant (25 by 50 km) tabular iceberg called C16 in the Ross Sea, Antarctica, during a uniquely accessible period (austral summer, 2003–2004) when it was aground against the northern shore of Ross Island. During the deployment period, C16 was in sporadic contact with another giant tabular iceberg, B15A, that was moving under the influence of local ocean currents. This study reveals that the C16‐associated IHT was a manifestation of extended episodes of discrete, repeating stick‐slip icequakes (typically thousands of individual subevents per hour) produced when the cliff‐like edges of the tabular icebergs underwent glancing, strike‐slip collisions. The IHT signal that we observed is thus not a phenomenon associated with iceberg elastic or fluid resonance modes, but is instead the consequence of long sequences of very regularly spaced and similar pulses of seismic radiation from these constituent stick‐slip subevents. IHT represents a newly identified glaciogenic source of seismicity that can be used to improve our understanding of iceberg dynamics and possibly of ice shelf disintegration processes.

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“…For instance, the occurrence of the unusually large iceberg B-15 (approx. 10 000 km 2 ), which calved from the Ross Ice Shelf, Antarctica, in March 2000 [26], is known to have strongly disturbed the Ross Sea ecosystem, from primary productivity to upper levels of the trophic web [25,27 -30]. In particular, local colonies of emperor penguins (Aptenodytes forsteri) experienced unusually high levels of breeding failure and of adult and chick mortality [29].…”

Section: Introductionmentioning

confidence: 99%

Environmental extremes versus ecological extremes: impact of a massive iceberg on the population dynamics of a high-level Antarctic marine predator

2012

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Extreme events have been suggested to play a disproportionate role in shaping ecological processes, but our understanding of the types of environmental conditions that elicit extreme consequences in natural ecosystems is limited. Here, we investigated the impact of a massive iceberg on the dynamics of a population of Weddell seals. Reproductive rates of females were reduced, but survival appeared unaffected. We also found suggestive evidence for a prolonged shift towards higher variability in reproductive rates. The annual number of females attending colonies showed unusual swings during the iceberg period, a pattern that was apparently the consequence of changes in sea-ice conditions. In contrast to the dramatic effects that were recorded in nearby populations of emperor penguins, our results suggest that this unusual environmental event did not have an extreme impact on the population of seals in the short-term, as they managed to avoid survival costs and were able to rapidly re-achieve high levels of reproduction by the end of the perturbation. Nevertheless, population projections suggest that even this modest impact on reproductive rates could negatively affect the population in the long run if such events were to occur more frequently, as is predicted by models of climate change.

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Tabular iceberg collisions within the coastal regime

Cited by 55 publications

References 40 publications

Sea ice freeboard in McMurdo Sound, Antarctica, derived by surface-validated ICESat laser altimeter data

Sea ice freeboard in McMurdo Sound, Antarctica, derived by surface-validated ICESat laser altimeter data

Seismic and hydroacoustic tremor generated by colliding icebergs

Environmental extremes versus ecological extremes: impact of a massive iceberg on the population dynamics of a high-level Antarctic marine predator

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