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

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

• Andrew J. Pershing
• University of Maine/
• Gulf of Maine Research Institute

Charles H. Greene Cornell University
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Collaborators
Ted Durbin URI
Charles Flagg SUNY Stony Brook
Sirpa Häkkinen NASA Goddard
Erica Head BIO
Dave Mountain NEFSC
Peter Smith BIO


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Outline

• Project goals
• Results
• Future plans

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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

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Gulf of Maine Regime Shift

• Hallmarks
• Abrupt shift in 1990, reversal in 2001
• Multiple trophic levels
• Strongest in autumn

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Possible Mechanism
Surface Salinity
Reduced surface salinity
Bigger fall bloom
Autumn Phytoplankton
Increased copepod reproduction (e.g. Durbin et
al. 2003)
MEPS 25481-100
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Salinity and Fall Stratification

• 1D Mixing Model
• Salty (1986) and Fresh (1998) initial TS-profiles
• 1980-1999 NCEP forcing

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Possible Mechanism
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Impact of Shift
Small Copepods
Calanus finmarchicus

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

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Impact of Shift
Small Copepods
Calanus finmarchicus
Herring
Right Whale Calves
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Impact of Shift
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Herring-Copepod Interactions

• Fall-winter larval herring
• Inefficient feeding

• Summer adults
• Efficient feeding

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Phytoplankton
Freshwater
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Phytoplankton
Freshwater
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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

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1990s Freshening
Salinity Change in the N. Atlantic
1990-1994
1995-1999

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

Figure courtesy of Tim Boyer, NOAA
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1990s Freshening

• Freshwater in early 1990s traced to Arctic
• NAO winds in late 1980s pushed Arctic ice out
• Increased outflow through Canadian Archipelago

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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