Interannual variability in hydrographic conditions: shipboard measurements and NERACOOS time-series Ruoying He1, Yizhen Li1 , Dennis McGillicuddy2 North Carolina State University1 Woods Hole Oceanographic Institution2 GOMTOX Project PI Meeting Dec6, 2010
Outline • Temperature, salinity and Rivers, Stratification • Currents • Wind • Significant wave height
Surface Temperature at B, E, I Surface Temperature in 2010 Was warmer than the seasonal cycle in the eastern GOM
Near-Bottom (50m) Temperature at B, E, I Bottom Temperature in 2010 Was warmer than the seasonal cycle in the eastern GOM
Surface Salinity at B, E, I Surface Salinity in April and May 2010 was comparable to the 2005 salinity condition, fresher than the seasonal cycle.
GOM River Runoff [104 ft3/s] River discharge data show that the overall freshwater runoff in 2010 was not anomalous.
However, the peak river discharge occurred in April, a bit earlier than most of other years. (shaded area indicates the spring and summer months)
Near-Bottom (50m) Salinity at B, E, I Bottom salinity in 2010 was also a bit fresher than the seasonal cycle.
Vaisala frequency estimated from 1m and 20m density at B, E, I ( Unit: /S^2*10^-4. ) Coastal water was largely stratified in the WGOM in April 2010, due to the lower salinity. The water was less stratified thereafter.
Subsurface temperature in Jordan Basin was 1-2 degree warmer than most of other years (Note bottom water was warm in 2006 and 2007 as well).
Upper-layer salinity in Jordan Basin was ~ 1 psu fresher than other years
Temperature at Northeast Channel (buoy N) In spring 2010, the temperature is constantly warmer than other years, indicating a deep warm slope water intrusion.
Salinity at Northeast Channel (buoy N) We didn’t see clear salinity anomaly in 2010 due to the data quality issue
Temperature at Scotian Shelf (buoy L) No data after 2008
Salinity at Scotian Shelf (buoy L) No data after 2008
Alongshore flow at buoy B in the WGOM Data Missing Relatively weak flow in the WGOM
Alongshore flow at buoy E in the WGOM Weak and steady flow(<5cm/s) at E except an early May stormy event.
Alongshore flow at buoy I in the EGOM Strong southward flow in April, and weak or even reversed coastal flow in May.
Cross-channel inflow at Northeast Channel (buoy N) No clear strengthening of deep inflow in the Channel
2007 EN 435 2007 EN437
2010 OC 460 2010 EN 476 Geostrophic flows in May and June 2010 are weaker than preceding years. Some northward coastal flow is found in May during OC 460 survey.
2010 OC 467 2010 OC 465 Coastal flow Was intensified in the WGOM by late June. intensified flow is also present in the WGOM by late July.
Long-term mean wind for the GOM (April, May and June) Long-term wind fields show an enhanced upwelling favorable condition from April to July
Wind Anomalies April Weak offshore blowing anomalies in April 2010
Wind Anomalies May Eastward wind anomalies in May 2010, with an upwelling anomaly component
Wind Anomalies June Upwelling-favorable wind anomalies in June 2010
Cumulative upwelling index for buoy B (WGOM) and E (EGOM) Wind in 2010 shows an overall upwelling-favorable condition.
30-day low-pass filtered wind (upper) and significant wave height (lower)). Blue line is the original hourly significant wave height time series. There is no clear evidence that the SWH is larger in winter 2009 and spring 2010.
Summary • GOM Water Temperature and Salinity Both surface and bottom temperature in 2010 is warmer than seasonal cycle in the EGOM. Surface Salinity in April and May 2010 was comparable to the 2005 salinity condition, fresher than the seasonal cycle. Bottom temperature is warmer in the Jordan Basin and Northeast Channel, indicating a deep warm water intrusion. • GOM Winds Upwelling index indicates that 2010 stands out to be upwelling favorable in summer. • GOM Rivers River discharge is in normal condition, but the plume occurs earlier in the season. • GOM Current and Transport The coastal flow is weaker than other years in April-mid June 2010, and enhanced in late June-August. • GOM wave height Significant wave height data indicate normal wave activity in winter 2009 and spring 2010, suggesting the possibility of cyst redistribution due to wave mixing/transport is small.
Hindcast of the 2010 GOM A . fundyense Bloom using the coupled Biophysical model Ruoying He1, Yizhen Li1 , Dennis McGillicuddy2 Don Anderson2, Bruce Keafer2 North Carolina State University1 Woods Hole Oceanographic Institution2 GOMTOX 2010 PI Meeting Dec 6-7, 2010
Sea Surface Height (SSH) modeled by HYCOM May 1, 2005 HYCOM ROMS (GOM) 1-3 km resolution ROMS (MAB-GOM) 6-10 km resolution Operational HYCOM (10 kmresolution) Hydrodynamic basis: multi-nested circulation modeling HYCOM: Hybrid Coordinate Ocean Model (NRL and U. Miami) ROMS: Regional Ocean Modeling System (Rutgers and UCLA)
Alexandrium fundyense Population Dynamics Model: (Consider cyst distribution, germination, growth and mortality) Reaction Advection Diffusion C: A. fundyense Cell Concentration u: velocity from the circulation model Upward swimming Wa=10 m/day(Kamykowski,1992) K: Diffusion coefficient from the circulation model Growth µ = min [ g (E, T, S) , g (DIN, T,S) ](Liebeg, 1845) “Mortality” m= f(Q10)(Durbin &Durbin, 1992; He et al, 2008) Fg:Cyst Germination Flux (Stock et al., 2005; McGillicuddy et al., 2005; He et al., 2008; Li et al., 2009)
Forcing Fields for the GOM Coupled Model Simulation -Physical circulation model • Tides (M2, S2, N2, K2, K1, O1, Q1) • 3-hourly wind and heat fluxes from NCEP NARR • River runoff from USGS gauges • Open boundary conditions from larger-scale ‘parent’ model -A. fundyense model • Net downward shortwave radiation from NCEP Reanalysis • Cyst abundance from fall 2009 cyst survey 3-D monthly • DIN climatology from U. Maine • Simulation period: Feb,1, 2010 – Jul, 28, 2010