JUNEAU ICEFIELD RESEARCH 1946-2003: GLOBAL WARMING DOCUMENTED IN THE LONGEST RECORD OF MASS BALANCE AND GLACIAL REGIMES IN THE WESTERN HEMISPHERE

For the past 57 years the Juneau Icefield Research Program (JIRP) has conducted a systematic study of key glaciers including the receding Mendenhall, Herbert, Lemon Creek, Norris, Twin, Llewellyn, and Cathedral Massif glaciers, and the advancing Taku and its distributary tongue, Hole-in-Wall Glacier. Special attention has been paid to mass balances of the Taku-Llewellyn glacier system, comprising a 110-km-long, south to north, transect profile. The two glaciers share a crestal névé at 2000 m elevation on the Alaska-Canada border.

A model has been developed with mass balance and surface flow-lag data showing relationships to general atmospheric circulation and to positions of the circumpolar vortex. From this model, observed glacier changes are explained for this critical region on the eastern rim of the Gulf of Alaska. From solar-induced natural climatic trends, the lowest point of cooling and allied accumulation maxima should be in the 1995-2000 time frame. JIRP records, however, reveal that since the early 1970’s the opposite has occurred. The most recent decade is the warmest in a century, with accelerated negative mass balances dominating the Icefield’s glaciers.

The seemingly anomalous continuing growth of the Taku Glacier is interpreted as a consequence of a significant inland shift in the mean position of the Arctic Front plus a notable upward shift of the mean freezing level. This trend has accelerated in recent decades, resulting in substantially more net-retained accumulation on higher névés of the Taku-Llewellyn Glacier system. A symptom of this condition is in the meteorological record revealing recent winters and springs as the warmest in the Alaskan panhandle for all of the 20th century. For the Arctic and sub-Arctic region as a whole, this research corroborates an increase in atmospheric trace element pollution and global warming with significant effect on human occupation and natural ecosystems in the Alaskan and Canadian Arctic.