Term 2 - Theme 3 (1) Flashcards
Observed sea level has increased around
10cm since 1970s.
Glaciers are driven by climate
Snow and ice accumulation, ablation through radiative forcing.
IPCC, 2001 + 2007
glaciers re the clearest indicators of what is currently happening to the climate of the earth… the fact that they are thinning and retreating at historically unprecedented rates should be a concern to us all.
Mass balance equation
MB = accumulation - ablation (-iceberg calving)
The cryosphere consists of
Northern hemisphere - Greenland, Arctic glaciers, Alaska, alps, himalayas (7m potential SLR).
Southern hemisphere - Antarctica - 57m potential SLR and the andes.
Change in glacier length
indirect, delayed sign of change in climate
Air temperature role
Related to radiation balance and solid/liquid precipitation ratio.
Climatic sensitivity of a glacier depends on
local topographic effects.
Response/lag time
Occur because the signal must be transferred from accumulation area to the snout of the glacier.
Response/lag time controlled by
glacier size, gradient and flow velocity. Lay, low gradient, slow glaciers will have a long lag time. Short, steep and fast glaciers will have a short lag time.
Monitoring frontal variations of glaciers
Direct measurement, image comparison.
Mass balance measurement of glaciers
Direct measurements of accumulation and ablation, remote sensing methods.
Global glacier changes (length)
General glacier recession shown in Little Ice Age. Intermittent readvances on decadal timescales. Strong glacier retreat in the 1920s and 1940s.
Glacier frontal variations
Most visible component of glacier response to climate change. May be studied over long time scales. All related to changes in total glacier mass balance.
global glacier change (mass balance)
mass balance is the different between mass gained and mass lost. Mountain glaciers are losing mass all the time + this has increased in the last decade.
Glacier fluctuation - Africa
occur on Rwenzari, Mount Kenya and Kilimanjaro In 1906 Rwenzari had 43 glaciers with a total area of 7.5km2. By 2005, this was about 1.5km2.
Glacier fluctuations - New Zealand
Most glaciers located along the Southern Alps . Overall retreat over the past 150 years, with intermittent Alpine radius in the 1890s, 19202, 70/80s and 1985. Ice cover estimated to have diminished by about 35% from 1850 to 1970s and another 22% by 2000.
Glacier fluctuations - Antarctica
Majority of glaciers and ice caps located on the Antarctic Peninsula. Cook et al (2005) showed that 87% of the glaciers have retreated over the last 6 decades. Glaciers on S Georgia receded overall since 9th Century.
Antarctic glacier change
Increasing atmospheric + oceanic temp. Air temps rose by 2.5 degrees in the northern antarctic peninsula. 1950-2000. Collapse of ice shelves. Acceleration of ice streams + outlet glaciers.
Glacier surface lowering
More surface lowering in the north related to greater temp increases. The thinning is likely to be related to glacier acceleration and increasing calving rates.
Prediction of future glacier changes are important for
understanding contribution to SLR, Managing water resources, mitigation against hazards such as GLOFs.
Prediction of future changes difficult due to
Uncertainty of future climate scenarios. Uncertainty as to how glaciers will retreat in future changes in climate. Local factors such as aspect and sliding.
Equilibrium line altitude (ELA) increased
in a warmer climate.
Prediction: topography
Steeper glaciers more likely to survive longer into a period of continental warming. Rise in eLA translated to a smaller zone of ice transferring from the accumulation to ablation zone.
The WAIS: marine ice sheet instablility
Major concern about the West Antarctic ice sheet size -much of the sheet is below sea level.
Nesje, A + Dahl, S, O (2000) the equilibrium line altitude marks
the area or zone on the glacier where accumulation is balanced by ablation.
Kieffer et al, 1994
The EOS has been developed to build uniform database of most glaciers in the world and monitor changes in glaciers on a periodical basis.
Paterson, 1994
The response time is defined as the time a glacier takes to adjust to a change in mass balance.
Johannesson et al, 1989
The response time is defined as the time a glacier takes to adjust to a change in mass balance.
During the Quarternary glacial periods, ice sheets were extensive, covering bout
30% of the Earth’s land area.
