Circulation characteristics of a shallow estuary plagued by water quality issues Janelle Reynolds-Fleming and Rick Luettich Institute of Marine Sciences UNC-Chapel Hill ERF Conference September 27, 1999

The Neuse River Estuary, N.C. 1. Be sure to point out Morehead City 2. Point out Cape Lookout 3. Point out Minnesott Beach and the Ferry 4. Point out New Bern

The Neuse River Estuary Quick Facts Drowned River Valley Part of Albemarle-Pamlico Sound system Average depth is ~3.6 m Length is over 70 km Average width is ~6.5 km Structure varies from “well-mixed” to “highly stratified” 14,550 km watershed area 1. Mention that the Albemarle-Pamlico Sound System is the top 5 largest estuaries in North America 2

Water Quality Issues Increased Residential, Industrial and Agricultural growth Declining water quality Outbreaks of algal blooms Periods of hypoxia and anoxia - seasonal Fish kills 1. Adversely affect local fishing economy as well as tourismand recreational boating. 2. In response to these issues, an effort to understand the circulation in the estuary was initiated in 1997.

Phase I: Questions What are the general circulation characteristics of the Neuse River Estuary? Influence of astronomical tide Influence of wind How does circulation influence stratification? Eventually: How does circulation influence dissolved oxygen levels and the occurrence of fish kills?

Phase I: Circulation Study - Instrumentation Two Moored S4s currents salinity temperature Moored water level gauge Shipboard transects hydrography, including D.O.

Phase I: Circulation Study NEUSE RIVER ESTUARY S4 mooring Water level gauge New Transect Locations Bern Broad Creek Trent River Arapahoe Brice Creek CROATAN 1. The S4 mooring was maintained from August 1997-September 1998 NATIONAL FOREST H148 H100 South H120 River Tucker Creek Adams N Cherry Creek Slocum South Point 10 miles Creek River Hancock Back Creek Creek 10 kilometers Clubfoot Havelock Creek

Phase I: Water Level Gauge

Power Spectrum for Water Level

Comparison with Tidal Signal

Coherence of Water level to wind Coherence Level

Phase I: S4 Time Series

S4 Time Series Data estuarine riverine Anti-riverine estuarine 1. The riverine section corresponds to a time when the Kinston discharge was really low. Throughout the month of July, discharge was less than 5.00 m3*10^6. 2. The riverine section also corresponds to the time period of August 1-2. The Met data shows that it was mostly cloudy over those two days, and only two of the 48 observations show “light rain.” Leads one to believe that circulation is more directly influence by wind. 3. Notice that during the riverine period, the winds are from the NE and during the typical estuarine, the winds are from the SW. Anti-riverine

Power Spectrum for velocity

Comparison with Tidal Signal

Along Channel Velocity vs. water level

Along Channel Coherence

Phase I: Shipboard Transects

Shipboard Transects - Alg. Channel Velocity July 29, 1998 12:29 July 29, 1998 17:32 NE 5-10 kts SW 15-20 kts -1.00 -1.00 -1.50 -1.50 ) m -2.00 -2.00 ( c e a f s u r -2.50 16.00 -2.50 w o b e l s ) / h m p t -3.00 c ( -3.00 e D m a 8.00 e r t -3.50 n s -3.50 w o 0.00 0.50 1.50 2.50 3.50 4.50 5.00 0.00 0.50 1.50 2.50 3.50 4.50 5.00 d July 30, 1998 00:05 S 5-10 kts S 5-10 kts 0.00 July 30, 1998 09:00 -1.00 s ) -1.00 D e p t h b l o w s u r f a c ( m ) Across Channel Distance from the North Shore (km) / m c ( m -1.50 -8.00 a e -1.50 r t p s u -2.00 -2.00 -16.00 -2.50 -2.50 -3.00 -3.00 -3.50 -3.50 0.00 0.50 1.50 2.50 3.50 4.50 5.00 0.00 0.50 1.50 2.50 3.50 4.50 5.00 Across Channel Distance from the North Shore (km)

Shipboard Transects - Acr. Channel Velocity NE 5-10 kts SW 15-20 kts July 29, 1998 17:32 July 29, 1998 12:29 -1.00 -1.00 -1.50 -1.50 ) m ( c e a f -2.00 -2.00 u r s w o l 16.00 e -2.50 b -2.50 h p t e ) D s / -3.00 m c -3.00 8.00 ( d a r w -3.50 h r t -3.50 0.00 0.50 1.50 2.50 3.50 4.50 5.00 o n 0.00 0.50 1.50 2.50 3.50 4.50 5.00 0.00 July 30, 1998 00:05 S 5-10 kts S 5-10 kts July 30, 1998 09:00 -1.00 s ) -1.00 -8.00 / m c ( d -1.50 a r -1.50 w h ) u t m -16.00 o ( s e c -2.00 -2.00 a f r -20.00 u s w o e l -2.50 -2.50 b h p t e D -3.00 -3.00 -3.50 -3.50 0.00 0.50 1.50 2.50 3.50 4.50 5.00 0.00 0.50 1.50 2.50 3.50 4.50 5.00 Across Channel Distance from the North Shore (km) Across Channel Distance from the North Shore (km)

Shipboard Transects - Hydrography SW 15-20 kts NE 5-10 kts 0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 -4.00 -3.50 -3.00 -2.50 -2.00 -1.50 -1.00 -0.50 July 29, 1998 13:00 0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 -4.00 -3.50 -3.00 -2.50 -2.00 -1.50 -1.00 -0.50 July 29, 1998 18:15 d i s o l v e x y g n ( m / ) 0.00 2.00 4.00 6.00 8.00 10.00 m ) ( h t d e p S 5-10 kts S 5-10 kts Across-channel distance from north shore [km] 0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 -4.00 -3.50 -3.00 -2.50 -2.00 -1.50 -1.00 -0.50 July 30, 1998 00:45 0.00 Across-channel distance from north shore [km] 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 -4.00 -3.50 -3.00 -2.50 -2.00 -1.50 -1.00 -0.50 July 30, 1998 09:45 d e p t h ( m )

Phase I Closure: Data Interpretation Water level influenced by wind and not astronomical tides Circulation controlled by: long period winds freshwater discharge short period wind forcing 12 hour seiching from Albemarle/Pamlico Sound Noticeable across channel velocity variability

Phase II Questions What are the major contributors to across channel circulation? What are the driving mechanisms of the 12 hour seiching? Can we quantify how wind direction, speed and duration influence currents? Eventually: Does across channel circulation contribute to fish kills?

Phase II: Circulation Study - Instrumentation Moored ADCP with CTD currents for entire water column at two locations point hydrography Vertical Profiling CTD hydrography for water column including D.O. Water Level Gauge Shipboard Transects currents hydrography, including D.O.

Phase II: Circulation Study NEUSE RIVER ESTUARY ADCP mooring and CTD Water Level gauge New Vertical Profiler CTD Bern Transect Locations Broad Creek Trent River Arapahoe Brice Creek CROATAN H68 1. The S4 mooring was maintained from August 1997-September 1998 NATIONAL FOREST H95 South H120 River Tucker Creek Adams N Cherry Creek Slocum South Point 10 miles Creek River Hancock Back Creek Creek 10 kilometers Clubfoot Havelock Creek

Phase II: Preliminary Data Northward Southward

Phase II: Preliminary Data Downstream Upstream

Conclusions Phase I Phase II will : provided general circulation data established future questions aided in the formation of Phase II study Phase II will : quantify the role of wind in across channel circulation explain the occurrence of seiching explain the role of circulation in fish kills