While the satellite record has been key in documenting large declines in the Arctic sea ice cover during the past four decades, the data record is still relatively short. To provide a longer record, scientists turn to the geologic record and proxy data. One approach is to analyze the age, transport, and deposition of driftwood. Driftwood distribution depends strongly on past sea ice conditions and ocean currents. New research using 913 driftwood samples collected across the western Arctic (Figure 6) has shed new insight on sea ice changes during the Holocene, between 12,000 years ago to present. During the early Holocene (12,000 to 8,000 years ago), the analysis suggests that the clockwise Beaufort Gyre dominated Arctic Ocean circulation, allowing more sea ice to stay within the Arctic Ocean. In the mid-Holocene (8,000 to 4,000 years ago), temperatures were higher and the Transpolar Drift dominated, leading to more ice export out of the Arctic Ocean through Fram Strait and less sea ice in the Arctic Ocean. In the late Holocene (4,000 years ago to present), the Beaufort Gyre once again strengthened as temperatures slowly cooled until the most recent several decades.
Remotely sensed data also plays an important role in data collection and consist of sensors attached to a platform. Sensors include cameras, digital scanners and lidar , while platforms usually consist of aircraft and satellites . In England in the mid 1990s, hybrid kite/balloons called Helikites first pioneered the use of compact airborne digital cameras as airborne Geo-Information Systems. Aircraft measurement software, accurate to mm was used to link the photographs and measure the ground. Helikites are inexpensive and gather more accurate data than aircraft. Helikites can be used over roads, railways and towns where UAVs are banned.