The North Atlantic OscillationThe North Atlantic Oscillation(NAO)(NAO)

Atmospheric Effects Atmospheric Effects of the NAOof the NAO

NAO +NAO +- Strong H and L pressure cells- Strong H and L pressure cells- Westerlies strengthen- Westerlies strengthen- Storm track shifts North- Storm track shifts North

NAO -NAO --Weak H and L pressure cells-Weak H and L pressure cells- Westerlies weaken- Westerlies weaken- Storm track shifts South- Storm track shifts South

North Atlantic Ocean Circulation North Atlantic Ocean Circulation Responses to the NAOResponses to the NAO

NAO +NAO +- Enhanced production of LSW and - Enhanced production of LSW and intensification of DWBCintensification of DWBC- Labrador Current weakens- Labrador Current weakens- Gulf Stream north wall shifts North- Gulf Stream north wall shifts North

NAO -NAO -- Reduced production of LSW and- Reduced production of LSW and weakening of DWBCweakening of DWBC- Labrador Current intensifies- Labrador Current intensifies- Gulf Stream north wall shifts South- Gulf Stream north wall shifts South

Emphasis on NW AtlanticEmphasis on NW Atlantic

The Winter The Winter NAONAO Index Index

1860 1880 1900 1920 1940 1960 1980 2000

42 0

-2 -4

Gulf of Maine/Georges Bank RegionGulf of Maine/Georges Bank Region

An oceanographic transition zoneAn oceanographic transition zoneespecially vulnerable to changes in climate.especially vulnerable to changes in climate.

NW Atlantic’s NW Atlantic’s Coupled Slope Water SystemCoupled Slope Water System

Maximum Modal StateMaximum Modal State- Associated with NAO +- Associated with NAO +

Minimum Modal StateMinimum Modal State- Associated with NAO- Associated with NAO - -

The Winter The Winter NAONAO Index Index

1860 1880 1900 1920 1940 1960 1980 2000

42 0

-2 -4

Progress of LSSW along Continental Progress of LSSW along Continental MarginMargin

Feb.98

Sep.97Oct.97

Feb.98

Jan.98

Mar.98

Intrusions of LSSW into Intrusions of LSSW into Gulf of MaineGulf of Maine

JanuaryJanuary AprilApril MayMay

SeptemberSeptember OctoberOctober NovemberNovember

NW Atlantic Response of NW Atlantic Response of Calanus finmarchicusCalanus finmarchicus to the NAO to the NAO

C. finmarchicusC. finmarchicus dominates dominates zooplankton biomass at high zooplankton biomass at high latitudes.latitudes.

Although an oceanic species, Although an oceanic species, C. finmarchicusC. finmarchicus populations populations dominate springtime dominate springtime production of many North production of many North Atlantic shelf ecosystems, Atlantic shelf ecosystems, including the Gulf of Maine.including the Gulf of Maine.

HYPOTHESIS:HYPOTHESIS:C. finmarchicusC. finmarchicus - an indicator of climate-driven - an indicator of climate-driven

changes in ocean circulation?changes in ocean circulation?

Since shelf populations of Since shelf populations of C. finmarchicusC. finmarchicus are are not self-sustaining and must be supplied every not self-sustaining and must be supplied every year or every few years from external sources, year or every few years from external sources, we hypothesize that their fluctuations in we hypothesize that their fluctuations in abundance reflect climate-driven changes in abundance reflect climate-driven changes in ocean circulation.ocean circulation.

Continuous Plankton Recorder Continuous Plankton Recorder (CPR) Survey of the North Atlantic(CPR) Survey of the North Atlantic

- SAHFOS supervises CPR surveys - SAHFOS supervises CPR surveys throughout most of North Atlantic.throughout most of North Atlantic.

- Sister CPR surveys on Scotian Shelf- Sister CPR surveys on Scotian Shelf and Gulf of Maine provide comparableand Gulf of Maine provide comparable plankton time-series data.plankton time-series data.

- Gulf of Maine CPR surveys are - Gulf of Maine CPR surveys are conducted by NMFS in Narragansett, RI.conducted by NMFS in Narragansett, RI.