anemometer: A scientific instrument that measures wind speed.
flux: How much of a substance moves through a unit of area per unit time. In other words, the rate of flow of a gas between a source and a sink.
greenhouse gas: A gas in the atmosphere that absorbs heat radiated by the earth and then emits it into the atmosphere, warming the earth's climate. Examples include carbon dioxide, methane, nitrous oxide, and ozone.
Greenland: The largest island in the world, a land mass of 836,000 square miles located above the Arctic Circle, just east of arctic Canada. Politically, Greenland is a self-governing province of Denmark. More than 80 percent of Greenland’s surface is covered by an ice sheet, which constitutes about ¼ of the world’s surface ice.
ice sheet: A mass of ice that permanently covers a very large area of land, is thick enough to fill in the land’s surface topography, and flows outward in many directions.
model: A tool, usually mathematically-based, used to represent a complex or large-scale process in simpler terms. Models are typically used to understand or predict the behavior of a system that cannot be directly observed in its entirety.
ozone: A form of oxygen that has three atoms, rather than the more common oxygen molecule’s two atoms. Ozone is produced naturally, by the energy in sunlight acting on oxygen molecules in the air, and by industrial and automotive processes. Ozone in the stratosphere absorbs most of the short-wave light from the sun that would otherwise reach the earth’s surface, protecting life on the surface from dangerous ultraviolet radiation. Ozone in the troposphere, on the other hand, is considered a pollutant; it can damage living tissue and break down certain materials, and it contributes to climate change.
ozone analyzer: The instrument constructed by our research team to measure the presence of ozone in tiny amounts near the snow surface.
ozone budget: The balance of exchanges (creation and loss) of ozone between sources and sinks, or between various environmental systems, such as the atmosphere and the biosphere.
parameter: A measurable variable that defines a characteristic of a system represented in a model. Parameters can be used as input into a model or can be estimated by the model.
photochemical: Of the chemical action and effects of radiant energy, particularly sunlight.
snowpack: A mass of snow that accumulates on the ground over the course of several snowfalls or even years.
stratosphere: The layer of atmosphere that includes the troposphere and the mesosphere; in other words, from about 15 kilometers (9 miles) to 55 kilometers (34 miles) above the earth’s surface. The temperature of the stratosphere is relatively constant.
sink: A system that absorbs a given trace gas or chemical.
sonic anemometer: A scientific instrument that measures wind speed using the properties of sound waves. Sonic anemometers are able to withstand storms and high wind speeds better than spinning-cup anemometers can, and are often used in extreme environments.
source: A system that emits a given trace gas or chemical.
Summit: A research station, sponsored by the National Science Foundation, at the highest point on the Greenland ice sheet. Summit is the site of our field experiments for this project.
troposphere: The layer of the atmosphere closest to the earth’s surface, reaching from the ground to 10 or 15 kilometers (6 or 9 miles) altitude. Temperature in the troposphere decreases with increasing altitude. Most of the earth’s weather (clouds, rain, etc.) is contained in the troposphere.