Increasing variance in North Pacific climate relates to unprecedented ecosystem variability off California

Abstract

Changes in variance are infrequently examined in climate change ecology. We tested the hypothesis that recent high variability in demographic attributes of salmon and seabirds off California is related to increasing variability in remote, large-scale forcing in the North Pacific operating through changes in local food webs. Linear, indirect numerical responses between krill (primarily Thysanoessa spinifera) and juvenile rockfish abundance (catch per unit effort (CPUE)) explained >80% of the recent variability in the demography of these pelagic predators. We found no relationships between krill and regional upwelling, though a strong connection to the North Pacific Gyre Oscillation (NPGO) index was established. Variance in NPGO and related central Pacific warming index increased after 1985, whereas variance in the canonical ENSO and Pacific Decadal Oscillation did not change. Anthropogenic global warming or natural climate variability may explain recent intensification of the NPGO and its increasing ecological significance. Assessing non-stationarity in atmospheric-environmental interactions and placing greater emphasis on documenting changes in variance of bio-physical systems will enable insight into complex climate-marine ecosystem dynamics.

Spring bloom dynamics and zooplankton biomass response on the US Northeast Continental Shelf

“…As demonstrated with our data on the shift in spring transition, the timing of physical events has shifted dramatically in the ecosystem. The Northeast Shelf ecosystem is experiencing wider swings in physical conditions (Mills et al, 2013) and biological responses, which would appear to reflect greater variation in the climate system impacting the ecosystem (Doney et al, 2012;Sydeman et al, 2013). There is an expectation that future climate conditions will impact bloom development in a number of different ways.…”

On the mechanisms of decadal variability of the North Pacific Gyre Oscillation over the 20th century

“…Di and Cloern et al [2010] further pointed out that the NPGO has more far-reaching impacts on the northeast Pacific ecosystem than the PDO, which is closely related to the primary factors of production such as the plankton and phytoplankton concentrations and thus can be used to track low-frequency climate changes in the central and eastern North Pacific oceanic ecosystem. With regard to the strengthening of NPGO in recent years and its associated increasing ecological influence [Sydeman et al, 2013], the NPGO has been heavily investigated [e.g., Di Lorenzo et al, 2008Furtado et al, 2011Furtado et al, , 2012.…”

Influence of Basin‐ and Local‐Scale Environmental Conditions on Nearshore Production in the Northeast Pacific Ocean

“…Growth of California Current rockfish was related to the PDO at the basin scale and to SST, SSHa, and freshwater discharge at the local scale. In the California Current, cooler conditions NORTHEAST PACIFIC NEARSHORE PRODUCTION were previously linked to increases in pelagic production, including rockfish growth (Lenarz et al 1995;Black 2009), rockfish condition (Lenarz and Wyllie Echeverria 1986), salmon catch (Hare et al 1999), reproductive success of the common murre Uria aalge (Gladics et al 2015) and Cassin's auklet Ptychoramphus aleuticus Wolf et al 2009), forage fish abundance (Sydeman et al 2013), zooplankton biomass and species composition (Peterson and Schwing 2003;Keister et al 2011;Di Lorenzo et al 2013), and chlorophyll-a concentrations (Harris et al 2009;Boyce et al 2010). These previous results are consistent with our findings.…”

“…Cooler conditions and decreased water column stability associated with coastal upwelling indicate greater vertical mixing and nutrient availability to primary producers in the California Current (Chavez and Messié 2009;Demarcq 2009). Increases in nutrient availability cause bottom-up increases in phytoplankton and zooplankton abundances and subsequent increases in forage fish consumption (Peterson and Schwing 2003;Harris et al 2009;Boyce et al 2010;Keister et al 2011), condition (Astthorsson and Gislason 1998;Robards et al 2002;Takahashi et al 2012), and abundance (Hedd et al 2006;Thayer et al 2008;Sydeman et al 2013). Furthermore, cooler conditions can prompt favorable shifts in prey composition (Hedd et al 2006;Mackas et al 2007;Thayer et al 2008;Keister et al 2011;Gladics et al 2015).…”

“…Basin-scale conditions could influence nearshore systems through their linkages to offshore or terrestrial systems, as basin indices correlate well with offshore sea surface temperature (SST), salinity, and upwelling (Di Lorenzo et al 2008;Ainley and Hyrenbach 2010) and with terrestrial indicators such as freshwater discharge (Royer et al 2001;Papineau 2001;Neal et al 2002;Hickey et al 2010). The Pacific Decadal Oscillation (PDO), North Pacific Gyre Oscillation (NPGO), and El Niño-Southern Oscillation (ENSO) represent both decadal (e.g., PDO and NPGO) and interannual (e.g., ENSO) scales of climate variability in the northeast Pacific Ocean basin (Hollowed et al 2001) and are among the most consistent predictors of marine and terrestrial ecosystem production in the North Pacific Ocean and western United States, respectively (Neal et al 2002;Mundy 2005;Spies 2007;Black 2009;Menge et al 2009;Di Lorenzo et al 2013;Sydeman et al 2013). Interpretation of basin-scale relationships and their linkages to nearshore responses could be improved by a complementary analysis of organismal growth responses to local conditions.…”