Terrestrial Ice: Glaciers

Mendenhall Glacier June 09
Another part of the cryosphere is terrestrial snow and ice. This part of the cryosphere is freshwater. Glaciers make up 2% of all of the water found on earth. Glaciers also contain 75% of the earths freshwater. Throughout geologic time glaciers have advanced and retreated. Each episode of a glacial advance or retreat caused climate change. The last ice age allowed native people to migrate to North America. The people were able to travel across land bridges created by lower sea levels. As the ice sheets melted the land bridges were submerged due to higher sea levels. The last ice age, known as the Wisconsin, changed cultures and climates throughout North America. At present we are in a warming interglacial period. The massive ice sheets in Wisconsin are long gone, but our present culture was shaped by ice. In Alaska glaciers still exist and the cultures here have also been influenced by the ice. Today our planet is warming and undergoing a climate change. As our planet warms ecosystems change creating changes in the native culture. (right Wisconsin 10,000 yr ago)

In Wisconsin we live in a land sculptured by ice. There are 100,000 lakes created by the last ice sheet. The ice sheets deposits are till in the form of gravel, our number one export. Our soil from the glacier is why whe have an excellent agriculture. Our freshwater is a gift from the glaciers. The great lakes exist due to glaciers. Our landforms include drumlins, eskers, kames, kettle lakes, outwash plains and moraine deposits. Today our winters are cold with lots of snow(around 90 in.), frozen ponds and lakes. The construction of homes and roads are influenced by the cryosphere. The freeze/thaw of the land causes houses to shift, sinking and rising landscapes and our roads to dip and buckle. (NASA satellite images of the Great Lakes July/December) Wisconsin is an example of a landscape created from a continental ice sheet. Due to a past global warming period the climate changed and the glaciers of 10,000 yr ago melted.

Today global warming is changing the glaciers in the arctic. The glaciers are melting because ablation is greater than accumulation of new snow . The climate today is causing the mass balance of a glacier to change. A glacier needs to accumulate more snow than melts for it to advance. The snow and ice of a glacier help control our climate. The white color creates a high albedo. By reflecting solar energy back into space, glaciers help keep our planet cool. As our warming trend continues more ice melts. As more ice melts the albedo decreases allowing less heat to escape, causing the melting of more ice, and less cooling. Another example of a positive feedback loop. Another change that takes place as a glacier melts back is the addition of vegetation where none existed before. New vegetation creates new ecosystems. At right the photos from the USGS Alaska Glacier Repeat Photography Project shows how the Muir Glacier has changed from 1940-2005. The bottom photo shows new vegetation. As glaciers melt the sea level will change. As icebergs melt the volume occupied by the iceberg will receive the meltwater and sea level will remain constant. Terrestrial ice as it melts will add water to the sea causing a rise. If only the Alaska glaciers melt the sea level would rise .05m, but if Antarctica ice sheet melts sea level would rise 73m. A dramatic rise like this will change the Atlantic coastline . Florida will be underwater. Disney will have to change it's rides. In the arctic glacial ice is thinning and snow accumulation is reduced. As the glaciers become smaller the culture will change due to changing ecosystems caused by new vegetation and animals to fill the niches in the ecosystem. As I talk to the elders in our village there is a concern of the changing climate and the consequences caused by the changes. They talk of when they were young how the ice formed earlier and remaned longer. The elders also speak of how the permafrost is changing. Permafrost is the reason the houses are built above the land. As warmer temperatures continue the active layer of the permafrost will increase. The permafrost contains tremendous amounts of carbon and methane gas. As plant matter decomposes methane gas is produced. As long as the permafrost remains frozen the methane gas is trapped. When the permafrost melts methane gas is released. Methane gas is a greenhouse gas the will increase global warming if large quantities are released into the atmosphere. The release of methane gas creates another positve feedback loop. More methane gas is released increasing the warming of the atmosphere which melts more permafrost and causes more methane to be released. The burning of methane gas from the ice on a lake around Fairbanks is a powerful video to show the students. Another change from melting permafrost is the amount of water the tundra is now able to absorb. When frozen, water remains on the surface as lakes. The melting of the permafrost increases the ability of the ground to absorb water. The lake water drains into the now thawed ground and become more shallow or completely disappear. The animals in the lakes die off or relocate to another area.

To study terrestial ice western science must use native knowledge about ice and permafrost. Traditional knowledge and direct observations of the native people can be vital in understanding snow and ice. The people of the north slope have survived for thousands of years. During that time climate has changed the people have adapted. Western science studies ice cores from Greenland, tree rings and keep data on ice flows. To blend the two cultures scientists need to use Alaskan students to help gather data. ALISON, the Alaskan Lake Ice and Snow Observatory uses students to collect data on lake ice. The data they collect is used and analyzed for climate and lake study.

Throughout geologic history ice ages have come and gone. The sheets of ice will come again. Each time the climate and the land have changed. Ecosystems change and adapt. This is a part of nature. Without glaciers and their effect on the land North America would be a much different place. Glaciers and ice allowed for the development of native cultures in Alaska. The remnants of glacial erosion and meltwater helped create the culture in Wisconsin. Today as the warming continues from both natural and cultural causes our climate is changing. As glaciers recede scientists need to understand how addtional meltwater will change sea level, ocean salinity, ocean circulation and climate. As more permafrost is melted methane gas is released into the atmosphere allowing more warm up to continue. Native and western science need to come together to better understand our natural world. Students of all cultures need to study about our planet and think about careers in science. As the arctic climate changes the native cultures will adapt like they have for thousands of years. They know and understand the land and how all things are connected better than anyone else. My job as a retired teacher is to use the resources from this class and educate the Wisconsin students about the arctic. They should also understand how the people of the arctic live and adapt to extreme conditions and how they have survived for thousands of years. They hunt in Wisconsin for sport, they hunt in the arctic for survival. Both students need to understand the science of climate and the changes occuring.