Any Questions? Glacier

Transcription

1 Geology of the Hawaiian Islands Class April 2004 Any Questions? Earth Systems Today CD Click on Weather and Climate Look at the sections on El Niño Ozone Hole Glaciers Why do we care? They help control global climate Glacier Body of ice, snow, firn,, and meltwater lying wholly or mostly on land showing evidence of present or former motion Glaciers form where more snow accumulates in winter than melts in summer. Types of Glaciers alpine: restricted to mountainous systems continental: : covers extremely large areas Antarctica: 12,500,000 km 2 up to 3 km thick, 80% of the ice on earth, 65% of the fresh water Greenland: 1,700,000 km km thick Sentinel Range, Antarctica Morphological classification Valley glacier Ice cap glacier Ice sheet glacier Greenland Ice Cap 1

2 Antarctic Ice Sheet Glacial Budget (Net Loss) Calving Glacier, Glacier Bay, Alaska Stages of Antarctic Ice Shelf Retreat Ice Flow in a Continental Glacier Glacial erosion V-shaped valley vs. U-shaped hanging valleys Creation of Hanging Valleys and Associated Waterfalls, Before and After Glaciation U-shaped Glacial Valley, Glacier National Park, Montana Glacial Polish, Striations, and Grooves, Glacier Bay National Park, Alaska Steve Kaufman/DRK Carr Clifton 2

3 Lateral Moraines Medial Moraines Pleistocene continental glaciation Great ice sheets extended into temperate regions 4 times in the past: Wisconsin Ma Illinoian Ma Kansan Ma Nebraskan Ma Northern hemisphere during the last glacial age Stephen J. Krasemann/DRK Photo Ice cores from the Vostok Station, Antarctica Advances and retreats of continental glaciers Worldwide and essentially instantaneous Implies Global climate control Oxygen isotopes and the record of global climate change Ordinary Oxygen has atomic mass of 16 (O-16) Oxygen-18 has 2 extra neutrons, so its atomic mass is 18 (O-18) Oxygen isotopes and the record of global climate change During glacial times, O-16 O is preferentially evaporated from the oceans because it is lighter O-16 is then precipitated and captured by glaciers, leaving the oceans with a higher concentration of O-18 Oxygen isotopes and the record of global climate change Foraminifera are small animals in the oceans that secrete calcium carbonate shells During glacial times, the oxygen in their shells is higher in O-18 O than O-16 O Millions of Years Before Present Isotopic record of changing ice volume over the past 2 million years based on deep-sea cores Fig

4 Glaciers and Sea Level Changes Lots of water in glaciers: during last ice age sea level lowered by ~130 m If all ice in glaciers today would melt, sea level would rise 65m: Major parts of Florida, Egypt, Hong Kong, London, Houston would be flooded What causes ice ages? Variations in Earth's orbit Changes in the atmosphere Changes in circulation of sea water Changing position/relief of the continents No single one of these explains all ice ages must be some combination. Geometry of Earth s orbital variations and tilt Global wind patterns Thermohaline Oceanic Circulation Global Circulation Patterns Established 4

5 The Hydrologic Cycle Circulation is cut off High Mountains Change Atmospheric Circulation Patterns 5

6 Ozone is a molecule formed of 3 Oxygen atoms (O 3 ) that forms a natural filter, absorbing the harmful rays of the sun. Chlorofluorocarbons in the atmosphere are attacked by UV radiation Chlorofluorocarbons in the atmosphere are attacked by UV radiation, liberating a chlorine atom Chlorine combines with O atoms Chlorine combines with O atoms to form ClO ClO atoms then attack Ozone ClO atoms then attack Ozone to liberate O 2 into the atmosphere 6

7 2 Ozone atoms are thus changed into 3 O 2 atoms The Problem: O 2 is transparent to harmful UV rays, so they pass through Effect of greenhouse gases on incoming and outgoing radiation The climate system CO 2 Fossil Fuels Atmospheric CO 2 measured at Mauna Loa Increases in CO 2 and use of fossil fuel Historical temperature changes Questions? Predicted increases in winter temperatures with doubling of CO 2 7

8 Thursday Last Web Class Kaua`i and the NW Hawaiian Islands Don t forget to do the last Virtual Field Trip and on-line quiz 8