Abstract
Year of emergence (YoE) is the year when an environment and the
organisms within begin to experience significant different conditions
(two times of natural variability) from the pre-industrial conditions
(~1770 C.E.). This study calculates the global surface
ocean YoEs for pH, partial pressure of CO(CO) and aragonite saturation
(Ω) from a recent calculated surface ocean carbonate chemistry data
product. The data product is calculated from the Surface Ocean CO Atlas
version 6 (SOCATv6) with modeled CO changes in the global surface ocean
from the ESM2M model. We find that CO, pH and Ω generally emerged from
preindustrial conditions in the open ocean by the year 1950, while these
properties have still not yet emerged along many ocean margins. We also
find that Ω had a significantly delayed YoE compared to pH and CO. The
delayed YoE for Ω is caused by its lasting sensitivity to temperature
variability, which increases the natural variability experienced by
organisms, and a partial cancellation of the long term acidification
trend by the global warming. Together, YoEs presented here highlight
that there are hotspots (open ocean) and coldspots (ocean margins that
were impacted by boundary currents) for the emergence of anthropogenic
signals. Continuous data collection and synthesis are needed to further
examine the impact of ocean acidification on ecosystem health.