Volcanic ash stimulation of marine primary production in the northeastern subarctic Pacific over the past 200 years
Abstract
Satellite data has shown a 9.3% decrease in marine primary production in the North Pacific over the past thirty years - the largest in the Northern Hemisphere. Because phytoplankton constitute the base of the marine food web and play a major role in the global carbon cycle, it is important to study the factors that affect their growth. One such factor in the iron-limited subarctic Pacific is volcanic activity - deposition of iron from volcanic ash. For instance, the 2008 Mt. Kasatochi eruption and the 2009 Mt. Redoubt eruption have both been linked to significant phytoplankton blooms. In this project, we analyze a portion of the Denali Ice Core to determine if such effects are observed consistently over the last 200 years. To estimate marine production over time, we use the time series of methanesulfonic acid (MSA), a byproduct of photosynthesis that has been shown to reliably record changes in phytoplankton growth. Eruptions are detected in two ways: by finding peaks in the residuals of high-pass loess de-trending of the non-sea salt sulfate time series; and by performing an empirical orthogonal function (EOF) analysis and finding peaks in the time series of a mode most likely to correlate with volcanic activity. We compare MSA levels in samples associated with eruptions detected with the non-sea salt sulfate method with MSA levels in all other samples with a series of randomization tests and find statistically significant (p<0.01) differences for eruptions detected in the winter and spring.We find significantly higher MSA levels in winter samples associated with eruptions in the same season and in summer samples associated with spring eruptions. These results suggest that volcanic eruptions occurring in the first half of the year stimulate marine primary production in the North Pacific for periods of 3 months or less.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.C11C1304O
- Keywords:
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- 0724 Ice cores;
- CRYOSPHERE;
- 1615 Biogeochemical cycles;
- processes;
- and modeling;
- GLOBAL CHANGE;
- 1616 Climate variability;
- GLOBAL CHANGE;
- 4994 Instruments and techniques;
- PALEOCEANOGRAPHY