Motyka, Roman J; Truffer, Martin; Fahnestock, Mark; Mortensen, John; Rysgaard, Søren; Howat, Ian M (2011): (Table 1) Annual melt rates of the South Branch of Jacobshavn Isbrae between July 1984-1985 [dataset]. PANGAEA, https://doi.org/10.1594/PANGAEA.817300, Supplement to: Motyka, RJ et al. (2011): Submarine melting of the 1985 Jakobshavn Isbræ floating tongue and the triggering of the current retreat. Journal of Geophysical Research, 116(F1), F01007, https://doi.org/10.1029/2009JF001632
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Abstract:
Photogrammetric reanalysis of 1985 aerial photos has revealed substantial submarine melting of the floating ice tongue of Jakobshavn Isbrae, west Greenland. The thickness of the floating tongue determined from hydrostatic equilibrium tapers from ~940 m near the grounding zone to ~600 m near the terminus. Feature tracking on orthophotos shows speeds on the July 1985 ice tongue to be nearly constant (~18.5 m/d), indicating negligible dynamic thinning. The thinning of the ice tongue is mostly due to submarine melting with average rates of 228 ± 49 m/yr (0.62 ± 0.13 m/d) between the summers of 1984 and 1985. The cause of the high melt rate is the circulation of warm seawater (thermal forcing of up to 4.2°C) beneath the tongue with convection driven by the substantial discharge of subglacial freshwater from the grounding zone. We believe that this buoyancy-driven convection is responsible for a deep channel incised into the sole of the floating tongue. A dramatic thinning, retreat, and speedup began in 1998 and continues today. The timing of the change is coincident with a 1.1°C warming of deep ocean waters entering the fjord after 1997. Assuming a linear relationship between thermal forcing and submarine melt rate, average melt rates should have increased by ~25% (~57 m/yr), sufficient to destabilize the ice tongue and initiate the ice thinning and the retreat that followed.
Project(s):
Coverage:
Latitude: 69.130000 * Longitude: -49.560000
Date/Time Start: 1984-07-24T00:00:00 * Date/Time End: 1984-07-24T00:00:00
Event(s):
Comment:
Data extracted in the frame of a joint ICSTI/PANGAEA IPY effort, see http://doi.pangaea.de/10.1594/PANGAEA.150150
Parameter(s):
| # | Name | Short Name | Unit | Principal Investigator | Method/Device | Comment |
|---|---|---|---|---|---|---|
| 1 | DATE/TIME | Date/Time | Geocode | |||
| 2 | Date/time end | Date/time end | Motyka, Roman J | |||
| 3 | Location | Location | Motyka, Roman J | |||
| 4 | Ice loss | Ice loss | km3/a | Motyka, Roman J | net loss | |
| 5 | Standard deviation | Std dev | ± | Motyka, Roman J | ice loss | |
| 6 | Surface ablation | Surf abl | km3/a | Motyka, Roman J | ||
| 7 | Standard deviation | Std dev | ± | Motyka, Roman J | surface ablation | |
| 8 | Melt rate, submarine | Melt rate subm | km3/a | Motyka, Roman J | ||
| 9 | Standard deviation | Std dev | ± | Motyka, Roman J | submarine melt rate | |
| 10 | Melt rate | Melt rate | m/a | Motyka, Roman J | average; equates to 0.62 m/day | |
| 11 | Standard deviation | Std dev | ± | Motyka, Roman J | average melt rate; equates to ± 0.13 m/day |
License:
Creative Commons Attribution 3.0 Unported (CC-BY-3.0)
Size:
10 data points