Ice bridge

An ice bridge is a frozen natural structure formed over seas, bays, rivers or lake surfaces. They facilitate migration of animals or people over a water body that was previously uncrossable by terrestrial animals, including humans. The most significant ice bridges are formed by glaciation, spanning distances of many miles over sometimes relatively deep water bodies.

An example of such a major ice bridge was that connecting the island of Öland with mainland Sweden approximately 9000 BC. This bridge reached its maximum utility when the glacier was in retreat, forming a low-lying frozen bridge. The Öland ice bridge allowed the first human migration to the island of Öland, which is most readily documented by archaeological studies of the Alby People.

In Jules Verne's 1873 novel The Fur Country, a group of fur trappers establishes a fort on what they think is stable ground, only to find later on that is merely an iceberg temporarily attached by an ice bridge to the mainland.

See also

Operation IceBridge

Operation IceBridge is a 2009–2016 NASA mission that aims to monitor changes in polar ice from a fixed-wing aircraft. It is a temporary replacement for the ICESat satellite until ICESat-2 launch in 2017.

Equipment

Since 2003 NASA has used a satellite, ICESat (Ice, Cloud, and land Elevation Satellite), for observing polar ice. ICESat was retired in February 2010 due to a technical malfunction, leaving NASA without a satellite dedicated to ice observance. A new satellite is not expected to be launched until 2016. NASA therefore introduced the IceBridge program which utilizes an aircraft to make similar measurements.

IceBridge flights began in October 2009 using a DC-8. Beginning in 2010, the DC-8 was joined by a P-3 Orion and other aircraft such as a King Air B-200, Gulfstream V and Guardian Falcon.

There are tradeoffs to using an aircraft instead of a satellite. One drawback is that a satellite can observe a far wider area. Also, satellites take measurements full-time, while IceBridge aircraft measurements are limited to annual campaigns that are several weeks long. Aircraft, however, have the advantages of being able to carry more instruments and target and focus on scientifically interesting areas instead of just flying a fixed path. Also, certain instruments such as ice-penetrating radar only work from the lower altitudes afforded by aircraft like the P-3 Orion and DC-8.