Periglacial Landscapes
Organization 1.Climate 2.Soils 3.Landforms and Hydrology 4.The front line on issues of climate change
Polar Climates
Dominated by Polar High Dense, cold air flows equatorward
Extreme Seasonal Changes 24 days in summer, 24 night in winter
Ice Cap Climate Mean monthly below zero
Tundra Climate harsh winters low average temperatures little snow or rainfall too short summer season for trees Influenced by permafrost, a layer of permanently frozen subsoil in the ground. The surface soil, which tends to be rocky, thaws in summer to varying depths. The combination of frozen ground and flat terrain impedes drainage of water. Held at the surface or soaking the upper layer of soil, the water forms ponds and bogs in low areas
Source: Solomon, 2000 Effect of Latitude or Altitude Our focus for this lecture
Animations – click on image Alaska Animations – focus on Arctic tundra where get extremes of temperature & little precipitation
Soils Poorly Developed In Rocky Areas
Soils Experience overturning from permafrost activity (gelisol)
Soils: position is very important Upland soils: entisols Poorly developed Lowland soils: histosols Peat – plant accumulation
In low-lying areas where water collects from permafrost melting, get accumulation of organic remains of plants called PEAT, or in soil-speak: histosol
Why does peat accumulate ? Production by plants exceeds decomposition Abundant growth due to available moisture during growing season Preservation of plants (cool conditions) Saturated conditions - slow, anaerobic decomposition by methanogenic bacteria When plants decay (with drying & warming), release of methane Videos of peat: Scottish Highlands; JumpingScottish HighlandsJumping
Landforms & Hydrology Permafrost Ice Wedge Polygons Pingo Patterned Ground Solifluction Rocky Uplands Rivers
Cryosphere Dominates Frozen Ice Caps & Frozen Water in Soil Frozen Ice Caps & Frozen Water in Soil (warning: very big file: 180 MB)
Permafrost Permanently frozen water in the ground
Underground mine in permafrost (Yakutsk, Permafrost Institute, Dr. P. Konstantinov)
When thaws, creates “thermokarst” Pipelines Break Roads Cave In
Buildings Collapse if not properly insulated
Natural Permafrost Cycle Freeze thaw = key to periglacial topography
Northwest Territories
Phoenix Lander on Mars Site selected because polygons suggest permafrost might be resent
Pingo Northwest Territories
Pingo
Can grow as water moves to ice core
Patterned Ground – Rocky & Flat Active layer “churning” sorts rocks
Northwest Territories
RMNP
Striped Ground, Greenland
Solifluction: sloped ground in finer materials flows (oozes)
Kinnard Research, Excavation, Yukon Excavation of lobe Buried organic layer
Topographic Position Rocky uplands: patterned ground Low slopes: solifluction lobes Lowlands: ice wedge polygons
Rocky Uplands Felsenmeer – rock block field broken up by frost weathering
Steep slopes with lots of frost- weathered rock: Rock Glaciers Ice core & seasonal freeze/thaw moves rocks
Possible Rock Glaciers on Mars?
Rivers Winter – frozen Spring – thaw Summer – very aggressive erosion
Sudden Thaw Floods Lena River Siberia
Breakup Timing
River Ice: Unique Arctic Hydrology All rivers experience some ice effect –In some instances, runoff events associated with river ice have produced extreme and dangerous flooding events River Ice interacts and obstructs the passing of floods Blockage causes water levels far higher than those under open water conditions
YUKON RIVER LIFTED AND SHIFTED SHEETS Shifted ice – large ice sheets that have moved short distances from their original locations as rising water levels create wider areas of open water into which the ice can move
TYPICAL RUN OF ICE May be miles in length Reach of large moving sheets (near breakup front) Reach of mixed sheets, pans, and chunks Reach of mostly chunks Subsequent runs are mainly chunks
YUKON RIVER Ice run – a continuous length of moving ice
NULATO RIVER ICE JAM Ice jam – an ice run that has stopped moving due to any of a variety of reasons; this very small jam has broken sheet ice holding back a small run of chunk ice
ICE JAM IMPACTS Upstream from the jam... Fast water level rise Packed ice chunks Potential flooding
Flooding impact Water outside the channel
KUSKO RIVER, ANI VILLAGE FLOODING Village flood – water spreading into a village that covers roads or threatens buildings
Lena River Delta Yukon R. Delta
Hansen, Scientific American, March 2004 Arctic Warming at the Front Line of Global Change
Dramatic changes in Arctic Sea Ice : Progressive Loss of Arctic Ice Imagine an ice-free Arctic
Source: Corell, R. W., 2004: Impacts of a warming Arctic. Arctic Climate Impact Assessment ( Cambridge University Press (
AnimationAnimation of Model Prediction NOAA Prediction of Arctic Sea Ice
Earth’s Orbital Parameters
Orbit and Ice Ages Tilt, Eccentricity, and Precession combine to cause variations in the amount of sunlight Earth receives...
Oxygen Isotope Record Oxygen isotope record of foraminefera During glacial periods, less oxygen in oceans...
The increase in growing season length over the last 50 years averaged for eight stations in Alaska having the longest and most consistent temperature records. Gradual Loss of Tundra (purple) as growing season lengthens
The future? Some modelsmodels show loss of TundraTundra (purple) From: Lawrence Livermore Laboratory