Mass Balance Features Derived from a Firn Core at Hielo Patagónico Norte, South America


Glaciological research was carried out in November and December 1996 in the accumulation area of Glaciar Nef, an eastward-facing glacier from Hielo Pata-g6nico Norte (Northern Patagonia Icetield), South America. A 14.5-m-deep tim core (9.7 m water equivalent: w.e.) was obtained at 1500 m a.s.l., and air tem- perature and melting rate were also measured. Values of 8180 of 1- or 2-cm-thick samples in the upper 6 m of the tim fluctuated from -16 to -10%0, which are explained by variations in 8180 of precipitation. Below 6 m in the tim, 8180 was almost constant, due to percolation of large amounts of meltwater. It was consid- ered that the upper 6 m was deposited during the prior winter; thus winter balance in 1996 was derived as +3.5 m w.e. Based on the measurement results and climatic data, winter and summer ablations were estimated at 0.0 and 3.4 m w.e., respectively, and summer accumulation at 2.1 m w.e. Then, net balance in the calendar year 1996 was estimated at about +2.2 m w.e. Comparison with previous studies and candidate drilling sites are also discussed.

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