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Cross shelf mixing of Fresh Water

Cross shelf mixing of Fresh Water In the New York Bight– annual and (speculatively) long-term variability. Bob Chant , Elias Hunter, Scott Glenn, Gordon Zhang, John Wilkin, Josh Kohut Rutgers University. Cross shelf mixing of Fresh Water

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Cross shelf mixing of Fresh Water

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  1. Cross shelf mixing of Fresh Water In the New York Bight– annual and (speculatively) long-term variability. Bob Chant , Elias Hunter, Scott Glenn, Gordon Zhang, John Wilkin, Josh Kohut Rutgers University Cross shelf mixing of Fresh Water In the New York Bight– annual and (speculatively) long-term variability. Bob Chant , Elias Hunter, Scott Glenn, Gordon Zhang, John Wilkin, Josh Kohut Rutgers University

  2. Mountain JGR 2003

  3. Without wind forcing model predicts that bulge continues to grow

  4. Outflow strongly modulated by low-frequency winds. Evident in both observation and modeling. (Choi and Wilkin, 2007) LaTTE ‘06

  5. Hudson outflow in shadow of Large scale ambient flows on MAB. Fong & Geyer JPO (2002)

  6. Salinity Following June/July ’06 floods Cross-shelf advection of fresh Water in response to persistent Upwelling favorable winds Glider Section Castelao et al. in press (JGR)

  7. Field data during weak “mean” winds revealed that small fraction (0.3-.05) of outflow immediately became incorporated in coastal current. Chant et al. 2008 (JGR). Choi and Wilkin, 2007 (JPO). Also outflow (and coastal current) highly responsive to wind forcing – even diurnal. Chant et al. 2008 (JGR). Hunter et al., 2007 (GRL).

  8. Retention of fluid in “bulge” was confirmed by dye tracer.

  9. Seasonal cycle of winds and river flow. NS winds EW winds River Flow Winds Ambrose Tower (1986-2007) Discharge Cohoes (1917-2007)

  10. Zhang et al (in prep) Fresh water pathways Based on 2 year ROMS Simulation. (explain red lines later)

  11. Zhang et al (in prep)

  12. Evidence of • Long term variability ? • Look at forcing • winds • River discharge

  13. Day of Peak Discharge Cohoes Record 2500 m3/s July 2006

  14. Discharge Discharge E/W E/W N/S N/S 1947-1977 1977-2007 Weakening of westerly winter and spring Discharge from Cohoes Wind from LaGuardia Airport (N/S winds biased vs. JFK & Ambrose) Day of Year

  15. Mean winds March/May Weakening of westerly

  16. Conclusions • Hudson’s outflow favors bulge formation • Bathymetric (Long Island) and outflow Geometry (stratified) • Apex– no favoring ambient flow. • 2) Fluid in bulge is highly responsive to wind forcing and rapidly disperses cross-shelf (first to east along LI then south with ambient flows). • 3) Fresh water is closer to shore in winter and off-shore during summer. • 4) Changes in the timing of the freshet and seasonal wind patterns would modify freshwater pathways. • 5) Role of cross-shore winds is unclear– but they appear to be weakening during freshet.

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