Using a biophysical mooring as a sentinel for ecosystem change: The story of M2

The National Oceanic and Atmospheric Administration's Ecosystems and Fisheries Oceanography Coordinated Investigations biophysical mooring site 2 (M2, 56.9°N, 164°W) time series, one of the longest running time series of its kind, has provided near-continuous biophysical measurements of the southeastern Bering Sea shelf since 1995. Since then, the array has evolved into four long-term monitoring sites stretching ~1000 km along the 70-m isobath of the eastern Bering Sea shelf. These biophysical mooring sites have been the cornerstone of an interdisciplinary fisheries-oceanography program since 1989, with over 300 surface and subsurface moorings spanning the Bering Sea. Basic biophysical measurements include temperature, salinity, currents, chlorophyll fluorescence, and nitrate; over time, CO2, pH, alkalinity, and passive acoustics have been added. Recently, innovative technologies have been used to supplement this long-term mooring infrastructure. Together these data provide unique interdisciplinary observations into the physical processes and changes of the southeastern Bering Sea.