Marine Ecosystem Responses to Climate-Associated Remote Forcing from the Labrador Sea

Andrew J. PershingUniversity of Maine/

Gulf of Maine Research Institute

Charles H. GreeneCornell University

Collaborators

Ted Durbin URICharles Flagg SUNY Stony BrookSirpa Häkkinen NASA GoddardErica Head BIODave Mountain NEFSCPeter Smith BIO

Outline

• Project goals• Results• Future plans

Goals

• Characterize interannual variability in physical and biological conditions in GOM/GB– Retrospective approach

• Identify drivers of variability– Focus on remote climate forcing

• Compare GOM with nearby regions– Scotian Shelf, MAB

Gulf of Maine Regime ShiftAutumn Phytoplankton

Small Copepods

Herring

• Hallmarks– Abrupt shift in 1990,

reversal in 2001– Multiple trophic

levels– Strongest in autumn

Possible Mechanism

Reduced surface salinity

Bigger fall bloom

Increased copepodreproduction

(e.g. Durbin et al. 2003*)

Surface Salinity

Autumn Phytoplankton

*MEPS 254:81-100

Salinity and Fall Stratification

• 1D Mixing Model• Salty (1986) and

Fresh (1998) initial TS-profiles

• 1980-1999 NCEP forcing

Possible Mechanism

Impact of ShiftSmall Copepods Calanus

finmarchicus

• Increase in small copepods, including Calanus copepodites• Decrease in adult Calanus

Impact of ShiftSmall Copepods Calanus

finmarchicus

Herring Right Whale Calves

Impact of Shift

Herring-Copepod Interactions

• Fall-winter: larval herring– Inefficient feeding

• Summer: adults– Efficient feeding

PhytoplanktonFreshwater

PhytoplanktonFreshwater

Discussion

• Importance of fall-winter period– Spring has dominated research

(e.g. GLOBEC) in NW Atlantic• Spring bloom, spawning of cod

and haddock– CPR data suggests that there is

considerable variability in fall• Fall ecosystem changes can

persist throughout the year

Fall phytoplankton

Haddock recruitment

1990s Freshening

1990-1994 1995-1999

Salinity Change in the N. Atlantic

Figure courtesy of Tim Boyer, NOAA

• Gulf of Maine freshening part of larger pattern extending into Labrador Sea– Non-local processes can influence Gulf of Maine

1990s Freshening

• Freshwater in early 1990s traced to Arctic– NAO+ winds in late 1980s pushed

Arctic ice out– Increased outflow through

Canadian Archipelago

Future Work

• CAFÉ Gulf of Maine Workshop III– Theme: Arctic Influences on NW Atlantic Shelf Ecosystems– November 7-8, GMRI, Portland, ME

• Compare Gulf of Maine with Mid-Atlantic Bight– Oleander CPR data set