Trends in discharge and flow season timing of the Onyx River, Wright Valley, Antarctica since 1969

Flow records at the two stream gauges on the Onyx River represent the longest actively collected
environmental records in the McMurdo Dry Valleys, Antarctica. The downstream gauge, near Lake Vanda, has been
collecting data since 1969, and the upstream gauge, at Lower Wright Glacier (LWRT), has collected data since 1972.
We analyzed these records to assess the long-term trends in annual discharge, flow season length, flow season start, and
flow season end. Our results indicate overall decreasing trends in annual discharge (0.4x106
m3
/decade at LWRT, 0.8
x106
m3
/decade at Vanda), and increasing flow season lengths (by 7 d/decade at LWRT, and 2.7 d/decade at Vanda),
influenced by earlier start and later end dates (5.2 and 0.8 d/decade, respectively at LWRT; 4.8, 1.4 d/decade,
respectively at Vanda). This suggests that flow season climate patterns in the Dry Valleys are decreasing glacier melt
intensity overall, but extending the period of meltwater generation