Multiple Stressors in ESM2M:
Time of Emergence
Jonathan Lin1, Keith Rodgers1, Thomas Froelicher2
1Princeton
University
2ETH Zurich
August 2014
Organizations and Host
• Princeton Environmental Institute
– “The Internship Program offers Princeton
undergraduates a unique opportunity to
complement their academic interests with handson, engaging, independent research and project
experiences through the summer months.”
• Atmospheric and Ocean Sciences (AOS)
Program
Background Information
• What is the ESM2M?
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Models physical climate (land, atmosphere, ocean and sea ice)
Incorporates interactive biogeochemistry (e.g. carbon cycle)
Internal variability (ENSO and other climatic modes)
Fully coupled model
• 30 member ensemble (1950 – 2100)
– Each ensemble member initialized with slightly different
atmospheric state (i.e. January 1, January 2, etc.)
– Each ensemble member is just one realization of all the possible
paths of progression
– Does NOT represent all possibilities, but rather just a range
Guiding Question
• What are the time scales of detectable trends
in four major stressors that control ocean
ocean ecosystem and marine organisms?
– Omega Aragonite (saturation state)
• Ωarag = [Ca2+] [CO32-] / K’sp
– Sea Surface Temperature
– Oxygen (integral over 100m – 600m depth)
– Primary Productivity
Time of Emergence: Method
• Signal to Noise Ratios
– Averaged linear trend (signal) divided by the standard
deviation (noise) among the 30 ensemble members
– Used a 30 year moving window for linear trends to
create signal to noise ratio over time (1965 – 2085)
• Mechanism
– Time of emergence when the signal to noise ratio
finally crosses a threshold
– Define the threshold as a signal to noise ratio of 2
(95% confidence of a detectable trend, a rather
conservative value)
Confidence Intervals
% confidence of Trend from 2005 – 2014. From top left, Ωarag,
SST, Oxygen Inventories, and Primary Productivity.
Confidence Intervals
• We can also look at
the combined
effect of the
stressors.
• Average of the %
confidence of all
four major
stressors, averaged
from 2005-2014
(top), and 20752084 (top).
Time of Emergence
Time of Emergence (95% confidence). From top left, Ωarag,
SST, Oxygen Inventories, and Primary Productivity.
Acknowledgments
• PEI for allowing me the opportunity to participate in
this internship
• Keith Rodgers, Thomas Froelicher, and Brendan
Carter for their initiation of this project as well as
their valuable mentorship and involvement in my
work