Hydrogen Peroxide, Formaldehyde and Sub-Annual Snow Accumulation in West Antarctica: Participation in West Antarctic Traverse

The industrial and natural activities that take place on the Earth's surface result in the release of chemicals to the atmosphere, including many that are dangerous to humans and to the health of our planet. If these chemicals were not removed from the atmosphere then their concentrations would continue to increase and our planet would become uninhabitable. But scientists have found that concentrations do not continue to increase, so there must be a cleansing process that removes these chemicals from the atmosphere and returns them to Earth's surface. One such cleaning process is called precipitation scavenging, where raindrops or snowflakes falling through the air capture these chemicals and deposit them to the ground. This movement of chemicals from the surface of the earth to the atmosphere and back is referred to as biogeochemical cycling.

Many of these chemicals are not easily captured by raindrops or snowflakes in the same form that they are released from the Earth's surface and so must undergo a transformation before they can be cleansed from the atmosphere by precipitation scavenging. The interaction of sunlight, water vapor, and other chemical compounds in the air produces very powerful cleansing agents called atmospheric oxidants. These atmospheric oxidants attack the chemicals released from the surface, making them more water-soluble so that they can be removed by precipitation scavenging. The amount of these cleansing oxidants in the atmosphere determines how long many chemicals released from the surface will stay in the air and what their concentrations are in the atmosphere. While the concentration of atmospheric oxidants varies around the globe and has changed in time throughout Earth's history, recent human activities such as the burning of gasoline and other fossil fuels have likely increased the rate of this change.

The main purpose of our research is to use measurements of certain chemicals in the snow and ice in West Antarctica to understand how human activities have changed the amount of these cleansing oxidants in the air. We study two chemicals, hydrogen peroxide and formaldehyde, which can tell us something about these oxidant concentrations over the past 200 years. We investigate the relationship of these chemicals in the snow, ice and atmosphere. If we fully understand this relationship, we can use the chemical concentrations that we measure in the snow and ice to reconstruct their concentrations in the air at the time the snow was deposited on the glacier. With the reconstructed concentrations of hydrogen peroxide and formaldehyde in the air and other information on atmospheric chemistry, we can use computer models to determine how concentrations of the cleansing atmospheric oxidants have changed over West Antarctica during the past 200 years.

The water cycle is the continuous movement of water from the oceans to the atmosphere through evaporation, back to the Earth's surface on the oceans and continents through precipitation as rain or snow, and then from the continents to the ocean through flow in rivers and streams. Hydrologists, meteorologists, and other scientists use measurements of precipitation to study Earth's water cycle. However, these measurements have only been made recently in Earth's history and only where humans have lived. Ice cores taken from mountain glaciers and the world's great ice sheets in Greenland and Antarctica provide very long records of precipitation and how precipitation has changed through time.

A secondary purpose of our research is to determine how long ago and during what season of the year the snow and ice collected in an ice core was deposited. The concentration of hydrogen peroxide in the air is determined mainly by the intensity of the sunshine and by the amount of water vapor in the atmosphere. Because the sun shines continuously in the relatively warm summer and not at all in the very cold winter, the concentration of hydrogen peroxide in the air over West Antarctica is very different during summer than in winter. This pattern in the air is transferred to the snow and may be trapped in the ice-core chemical record. Much like a tree ring, the pattern of high summer and low winter concentrations of hydrogen peroxide in an ice-core record allows us to count annual layers of snow accumulation. By measuring the thickness of each year's snow layer, we can determine the amount of precipitation that accumulated as snow that year at the ice core location. In addition, we hope to use these ice-core chemical records to tell us how much snow has fallen during each season at the ice-core site and how this seasonal timing of snowfall may have changed during the past 200 years.

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