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Climatic Influences on Coastal/Estuarine Physical Oceanography …and Possible Interdisciplinary Implications
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Climatic Influences on Coastal/Estuarine Physical Oceanography …and Possible Interdisciplinary Implications

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Climatic Influences on Coastal/Estuarine Physical Oceanography…and Possible Interdisciplinary

Climatic Influences on Coastal/Estuarine Physical Oceanography…and Possible Interdisciplinary
Implications
Dan Codiga
URI/GSO

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Climatic Influences on Coastal/Estuarine Physical Oceanography …and Possible Interdisciplinary Implications Climatic Influences on Coastal/Estuarine Physical Oceanography …and Possible Interdisciplinary Implications Presentation Transcript

  • Climatic Influences on Coastal/Estuarine Physical Oceanography…and Possible Interdisciplinary Implications Dan Codiga URI/GSO
  • Coastal and Estuarine Physical Oceanography Key processes  Currents, circulation: transport rates & pathways  Competition b/w stratification and vertical mixing  Exchange: Advective and dispersive transfers b/w estuarine (fresher) & coastal (saltier) Systems are highly dynamic/variable on numerous timescales: tidal (~<1 day), weather-event (3-6 days), spring-neap (14-28 days), seasonal, inter-annual, … climatic
  • Local Laboratories:Estuaries, Coastal Seas/Sounds, the ShelfDominant river inputs Examples Ex 3 later in talk Ex 1 Ex 2
  • Satellite Sea-Surface Temperature(AVHRR averaged 2004-2008, Codiga & Ullman 2010 OSamp Part I)WINTER SPRING Long Island Sound outflow a nt ront oy w F Bu tflo OuSUMMER FALL
  • In a few days, changing winds &/ river runoff can dramatically reposition the buoyant outflow frontWINTER SPRING vent W eather-e shiftsSUMMER FALL
  • Climate-Sensitive Influences River runoff (precipitation)  Strength and persistence of stratification  Strength of estuarine exchange circulation  Offshore extent of freshening Wind speed; and Wind direction  Vertical mixing; Surface cooling; Upwelling flow strength; Estuarine exchange strength; Transport pathways Surface heating  Distributions of temperature, stratification Storm frequency and intensity  Extreme events
  • Estuarine exchange circulation Estuarine River inputUp exchange Estuary Less More Dense dense Ocean Head (Lines of constant density) Exchange commonly 10-30X river input Exchange increases as river input increases, and as stratification increases Density structure maintained by complex interaction between advection and mixing
  • Asymmetric Response to Wind Down-estuary wind Up-estuary windUp Before After •Strengthened stratification •Weakened stratification •Wind-driven vertical mixing •Wind-driven vertical mixing less effective more effective •Enhanced exchange flow •Reduced exchange flow Mixing is sensitive to alignment of wind relative to estuary axis In LIS: Whitney and Codiga JPO, In press Wilson and Wang, Submitted
  • Expected trends & possible consequences Increased streamflow/precipitation & surface heating  Stronger stratification, increased estuarine exchange rate  Possible transition from mixed estuary to partially stratified, or from partially stratified toward salt wedge  Larger offshore extent of freshening/stratification Changed mean wind direction  Increased/decreased vertical mixing and estuarine exchange, depending on alignment with local estuary axis Decreased mean wind speed  In estuaries, weaker mixing  On shelf, weaker upwelling circulation Increased storminess  More frequent extreme events, more rapid dispersion
  • Potential Interdisciplinary Drivers Higher river flow  (Estuaries) Increased stratification, nutrient load, primary productivity… increased spatial extent and intensity of hypoxia  (Shelf) Greater offshore extent of freshening influence… potential new transport pathways and geographic extent of HABs Decreased mean wind speed  (Shelf) Weaker upwelling circulation, reduced primary productivity  Different rates of dispersal, transport and flushing Changed wind direction (relative to shoreline geometry)  (Estuaries) Altered vertical mixing  New transport pathways & rates Increased storminess  More rapid dispersal of waterborne materials  More frequent habitat alterations (salinity, temperature)
  • Three examples Estuarine exchange flow between Long Island Sound and coastal ocean Rhode Island Sound extreme event: Deep pulse of slope water from ~100km to south Inter-annual variability of Narragansett Bay stratification and hypoxia
  • Long Island Sound Exchange Codiga and Aurin, CSR 2007 Several years 8-times daily ADCP transects (ferry) Transport strongest in summer, when stratified Increased river runoff should increase stratification Suggests future exchange flow will be stronger Shorter estuary flushing time – could ameliorate hypoxia  Contrasts expected enhanced hypoxia due to increased stratification
  • Fall 2009 Deep Slope-waterIntrusion to Rhode Island Sound  Warm salty water with T & S well higher than climatic averages (based on decades of observ’ns)Ullman & Codiga 2010 OSamp Part II
  • Buoy time series during fall cooling Ullman & Codiga 2010 OSamp Part II Sudden arrival, present for ~weeks T & S values imply origin over continental slope ~100+ km south Possible Gulf Stream ring/streamer remnant Ecological implications (larval transport, habitat, …)
  • Narragansett Bay Inter-AnnualStreamflow/Hypoxia Variability  Springtime streamflow good predictor of summer stratification and hypoxia  Wet conditions enhance hypoxia  Suggests worsening future Codiga et al 2009, Estuar. Coast. hypoxia