Document Type

Honors Thesis

Publication Date

Spring 5-2018

Abstract

Climate change is expected to significantly affect the world’s fjords by increasing storm intensity and glacial lake outburst floods (GLOFs). GLOFs are characterized as a sudden release of glacial trapped waters into a fjord, yet how they modify fjord circulation and zooplankton migration patterns is not well understood. This study aims to investigate long-term physical and biological patterns in fjords and how they are modified by GLOFs by characterizing intra-annual variation in fjord hydrodynamics and biology. The study area is Martinez Channel in Chilean Patagonia located below the Northern Patagonia Ice Field. To accomplish this goal, circulation patterns and temporal and spatial variations of zooplankton will be analyzed in the presence of a GLOF and under normal conditions. The data collected include horizontal current velocities measured throughout the water column with a moored (~80 m depth), upward facing, acoustic doppler current profiler (ADCP) which sampled hourly in 1 m vertical bins. Salinity, temperature, wind, and river discharge data were also analyzed to complement the velocity measurements. Results showed that the baroclinic annular mode (BAM), a proxy for storminess in the Southern Hemisphere, significantly influenced the fjord every ~20-30 days. The BAM induced mixing which caused pycnocline depressions that interacted with the diel vertical migration of zooplankton. The strong winds associated with the BAM were also enough to retain floodwaters from the GLOF in early February. This study proves that external events such as the BAM and GLOFs affect fjord physics and biology and should be considered in future studies.

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