Lecture 13 - Glaciers and Climate Change Flashcards
Carr et al (2013)
Marine terminating outlet glaciers can undergo dramatic change at annual timescale
marine terminating outlet G = channel of fast moving ice that drains an ice cap/sheet and terminates in the ocean, either a floating or grounded Margin
G’s resting on reverse bed slopes may be unstable - sunG topo can causes changes in marine terminating outlet dynamics independent of climatic/ocean forcing
- more focus needed on Fjord impact
Carr et al (2013) Arctic marine terminating outlet Gs
large uncertainties of response to forcing across Arctic, danger of extrapolating rates of mass loss from small sample of study Gs
Arctic expected to reach 4-7dc by 2100 –> rapid change ic ice masses –> contribute to SL (SL change prediction in crucial)
PIG highlights the coupling of outlet Gs and ice streams with ice sheet interior causing vulnerability to mass loss
Carr et al (2013) Marine terminating Gs response to forcing
3 primary oceanic/climatic controls on outlet G dynamics (not independent, and connect):
- air temp
- ocean temp
- sea ice concentrations
important G specific controls on behavior = subG topo, Geology, fjord bathymetry/topo, sed at GL and g velocity, size, surface slope, catchment area
responses to atmospheric warming include: hydrofracture of crevasses at terminus/lateral margins, MW enhanced sub marine melting via plume circulation, sea ice loss
numerical modeling improved understanding but still need developing
IMBIE team (2018)
Antarctic ice sheets response to climate change drives SL rise (~7.66 contribution to mean SL 1992-2017)
(holds enough to increase SL by 58m)
uses 24 individual estimates which use satellite altimetry, gravimetry and mass budget methods : next could use Airborne snow radar as MB assessment, could re-assess the satellite measurements from 1990 (may address the imbalance that is present in the current record)
- should separate MB record into contributions due to short term fluctuations in surface MB and longer term trends in G ice
ice shelf collapse at APIS –> rapid mass loss of inland loss in 1990s
large variations in EAIS estimates
reduced thickness and extent of floating ice shelves –> disturb inland ice flow –> trigger retreat, acceleration and drawdown of many marine terminating ice streams
Jacob et al (2012)
recent global MB of glaciers and ice caps rely on extrapolation of sparse MB measurements so overall contribution to SL unclear
using GRACE to calculate mass change; monthly global gravity field solutions, 175 ‘mascons’
correct for hydrology and glacial isostatic adjustment
total contribution to SL rise of all ice covered regions ~1.48 mm/yr, matches German GRACE field by 5%
Alaksa - considerable mass loss, but less than previous GRACE rates
high mountain areas have considerable annual varibility, but disagrees with a lot of previous studies –> more research
lack of large grace in HMA, could be due to tectonic uplift offsetting the negative mass loss
Miles et al (2016)
EAIS, Pan Ice sheet
40 years satellite imagery
- most Gs retreated 1974-1990 before advancing in every drainage basin 1990-2012
- only exception = Wilkes land, 74% Gs retreated 2000-2012: overlies large marine basin, possible future SL rise from this part of EAIS
Retreat due to
- fall in sea ice
- associated impacts on ocean stratification –> incursion of warm deep water towards G termini
- excess surface MW –> hydrofracturing –> disintegration of ice shelves
Amudsen sea, WAIS, upwelling of warm circumstances polar deep water 00> increased discharge of outlet Gs
Carey (200%)
certain conditions can effects the degree to which natural disasters impact peoples homes and livelihoods (e.g. location, income)
Peru Cordillera Blanca G retreat –> triggered some of worlds most deadly avalanches and G outburst floods (nearly 30,000 deaths since 1941)
increased El niño frequency
