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SURFACE WATER DRIFT SOUTH OF CAPE LOOKOUT_ NORTH CAROLINAl C. A.

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					                               SURFACE    WATER   DRIFT

                     SOUTH OF CAPE LOOKOUT,       NORTH    CAROLINAl




                        C. A. Barans     and W. A. Roumillat




                     Marine   Resources    Research   Institute
           South Carolina Wildlife     and Marine Resources Department
                        Charleston,    South Carolina 29412




                           Technical     Report   Number   12




                                   August,    1976




IThis work is a result of research sponsored by the National Marine Fisheries
 Service (MARMAP Program Office) under Contract Number 6-35147 and by the
 South Carolina Wildlife and Marine Resources Department.   MARMAP Contribution
 Number 126.
                                               2

                                                    parallel to degrees of latitude. Drift
 Acknowledgments                                    bottles were also released at 51 ground-
                                                    fish trawling stations between Cape Fear,
      We thank: V. G. Burrell, Jr., P. A.           North Carolina and Cape Canaveral, Florida
 Sandifer, and F. W. Stapor for critically          during a cruise in September 1975. Bottles
 reviewing the manuscript; George Miller            were dropped at eight stations on a single
 and the NMFS, Southeast Fisheries Center           north-south transect through Onslow Bay
 for supplying and forwarding the return            during a cruise of the R/V Palumbo in
 cards; Larry Atkinson of SkidawayInstitute         March 1975 in cooperation with the NMFS's
 in Georgia for suggestions and assistance          Atlantic Estuarine Fisheries Center,
 at the initiation of the study; NMFS,              Beaufort, North Carolina.
 Middle Atlantic Estuarine Fisheries Center
 for releasing bottles in Onslow Bay during             An attempt was made to limit releases
 March; Sue Broadbent, Bill Leland, Ann            to surface waters inshore of the Florida
 Leonard, Dan Lesesne, Oleg Pashuk, and            Current, which was identified by its
 Terry Read of the shipboard staff and             seasonal temperature and salinity charac-
 vessel captain, John Causby and crew for          teristics. However, during the September
 their supporting effort; Lexa Ford and            1975 cruise, some bottles were released in
 Kathleen Meuli for typing and Allene Barans       the Florida Current. Recoveries from most
 and Evelyn Myatt for illustrations. This          cruises were calculated on the basis of
'work is the result of research sponsored          the total number of bottles released during
 by the MARMAP Program, U. S. Department of        the cruise; recoveries from the September
 Commerce, National Oceanic and Atmospheric        1975 cruise were calculated on the basis
 Administration, National Marine Fisheries         of releases inshore of the Florida Current.
Service.

                                                        At each station of each cruise, with
Introduction                                       the exception of the March cruise, a water
                                                   temperature profile was made with an
     The patterns of surface water move-           expendable or mechanical bathythermograph,
ments directly influence the distribution          and surface water temperatures and
of many near surface phytoplankton, zoo-           salinities were taken.
plankton, nutrients and pollutants. The
most comprehensive review of information            Results
to date on circulation of waters over the
continental shelf south of Cape Hatteras                Total card recovery was 13.8% of the
(Bumpus, 1973) concluded that this area is         number of drift bottles released; the
a complex and variable system of interact-         greatest part of the recovery (12.1%) was
ing forces greatly affected by the shifting        from bottles released in September, both
Florida Current.                                   in 1974 and 1975. The fewest returns were
                                                   from releases during November 1974.
     The Marine Resources Research
Institute (MRRI) of the South Carolina                   During September 1974 and 1975 many
Wildlife and Marine Resources Department           cards were recovered in northern Florida
has joined with the National Marine                 (Figs. 1 and 2) from bottles released
Fisheries Service to investigate factors           south of Frying Pan Shoals (the submarine
controlling marine fish distributions be-          projection of Cape Fear). Release sites
tween Cape Fear, North Carolina and Cape           during 1975 ranged over a greater shelf
Canaveral, Florida as part of the Marine           area and corresponded to recoveries over
Resources Monitoring Assessment and Pre-           a large segment of the southeastern coast-
diction (MARMAP) Program. To accomplish            line (Fig. 2), while a release area north
this objective, MRRI has initiated several         of Charleston in September 1974 resulted
studies of the physical and chemical               in recoveries concentrated only in northern
oceanographic conditions of this region in         Florida (Fig. 1). In September 1974, there
conjunction with major studies of ichthyo-         were no returns from bottles released north
plankton and groundfish. The objective of          of Frying Pan Shoals, while in September
this study was to further describe surface         1975, two returns were obtained north of
water movements south of Cape Lookout,             the Shoals (Table 1). During September
North Carolina.                                    1975, bottles released north of Frying Pan
                                                   Shoals generally were recovered northeast
~ethods                                            of the release point, while those released
                                                   immediately south of this physiographic
     Drift bottles containing preaddressed         feature were recovered to the northwest
return cards of the type described by              (Fig. 2).
Norcross and Stanley (1967) were released
at a total of 272 stations (5 bottles per               Return locations from the few bottles
station). Primary releases (213 stations)          released in or at the edge of the Florida
were made between Cape Lookout, North              Current during September 1975 were vari-
Carolina and Charleston, South Carolina            able in direction. From one station
during four cruises of the R/V Dolphin             approximately 115kmdue east of Charleston
(September and November 1974, January and          at the edge of the Florida Current, two
April 1975). Stations were located at              bottles were recovered in opposite direc-
18.5 km intervals along 4 to 6 transects           tions. One bottle was recovered just south
                                                                                                                                                                                                                                                                     --

                                                                                                                                                                                      3




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                                         .                            II                               I                                                                              No, Release Stations - 62
                                                                                                                                                                                        Total Recovery - 18,1%
32~;~                                                         J                                       J                                                                         Range in Recovery Time - 26-134 days
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  Figure 1. Drift Bottle Cruise                                                                                                                                   September                     15-18, 1974.        Open circles indicate
  release  stations;    solid circles                                                                                                                              indicate                     release    stations    from which bottles
  were recovered;    arrows indicate                                                                                                                               probable                     drift   direction     and area of recovery.
                                                                                                          4




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      Savannah'/                                                                                                         Total Recovery - 43.1 %
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  Figure 2.                      Drift Bottle Cruise August 31                                                              -             September19, 1975.                  Open circles
  indicate release stations; solid circles indicate release stations from which
  bottles were recovered; arrows indicate probable drift direction and area of
  recovery.
                                                                    5

of Cape Hatteras in 23 days and the other                                     Fear and Lookout, with returns limited to
just south of Jacksonville in 64 days at                                      only north of release sites (Fig. 5). In
approximately equal distances (376-384 km)                                    April, card returns from releases north of
from the release point. A single recovery                                     Frying Pan Shoals were primarily northeast
from a release about 59 km due east of the                                    of release positions, while releases south
above station (completely under the influ-                                    of Frying Pan Shoals were recovered north-
ence of the F1orida.~urrent) also was made                                    west of release positions (Fig. 6).
just north of Cape Canaveral. A nearshore
release within the waters of the Florida                                           Current speeds were calculated using
Current just north of Cape Canaveral                                          the first recovery date from each release
resulted in a northward movement (98 km)                                      station (Table 1). Calculated rates of
and recovery of two bottles.                                                  surface water movement south of Frying Pan
                                                                              Shoals ranged from 1.5 km/day in April to
     In November, there were no returns                                       11.3 km/day in September, while inferred
from bottles released south of Frying Pan                                     rates north of the Shoals ranged from 2.4
Shoals, and only a single return north of                                     km/day in November to 12.7 km/day in April.
a release position north of the Shoals                                        Pronounced differences existed in card
(Fig. 3). In January, returns were simi-                                      recoveries (Figs. 1-6) and monthly calcu-
lar to those in November (Fig. 4). In                                         lated current speeds (Table 1) for drift
March, releases were confined to Onslow                                       bottles released north and south of Frying
Bay, a body of water insulated by Capes                                       Pan Shoals.




      Table 1.       Drift     bottle    recovery   relative   to   release     north    or   south     of   Frying    Pan   Shoals.




                     Average Direction               Average Distance             Average Speed                    Recovery as
                        From Release                From Release (Km)                Km/day                     % of Total Release
                                                                                                                   Each Cruise
                      North         South            North      South             North         South             North    South



 September      74        NR            2100           NR           489                 NR       11.4                  NR         18.1

 November 74              0630          NR            100           NR              2.4           NR                  0.3          NR

 January        75        0680          NR             46           NR              3.1           NR                  1.1          NR

 MarchI         75        0050           -             14           -               2.9           -                   22.5             -
 April          75        0600          3500          102           33             12.7           1.5                 0.7          3.3

 September 75             0240          20102           77      2042                3.3           6.62                0.0+        43.1



          No   Releases


 NR   =   No Recoveries

 1 Releases      only in Onslow         Bay; 8 stations.

 2 Calculation does not include returns from 2 stations directly                              south of Frying         Pan Shoals,          bottles
   of which were recovered northwest of release positions.
                                                                                                                                       6



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                 ~.~I#                                                                   '                                                         No, Release Stations - 59
                                                                                                                                                    Total Recovery - 0,3 %
32J:~
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                                          '                                          .                                                 Range in Recovery                               Time                  -     42 days

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     Figure 3. Drift Bottle Cruise November 7-14, 1974. Open circles indicate
     release stations; solid circles indicate release stations from which bottles
     were recovered;arrows indicate probable drift direction and area of recovery.
                                              7




         79°                    78°    77°                  76°                     75°



                                                                                                35°




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                                                  No. Release Stations         -   37
                                                    Total   Recovery   -   LI %
32                                           Range in Recovery Time - 28 - 63 days


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                                                                                                29°




30



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                                      80°           28°     79°                    78°    77°




 Figure 4. Drift Bottle Cruise January 17-27, 1975. Open circles indicate
release stations; solid circles indicate release stations from which bottles
were recovered; arrows indicate probable drift direction and area of recovery.
                                                                   8



          79°                78°                             77°                  76°            75°


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                                                                       No. Release Stations - 8
                                                                         Total Recovery - 22.5 %
                                                                   Range in Recovery Time - 1-26 days


                                                                                                                      30



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 Figure   5.        Drift Bottle Cruise March 12-14, 1975.                              Open circles indicate
release stations; solid circles indicate release stations from which bottles
were recovered;arrows indicate probable drift direction and area of recovery.
                                                                                                                          9



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      "t,-"-",W                                                                  ....                                             No. Release Stations- 55

       ~~'~'""'"                                                             !                                                             Total      Recovery        - 4.0%

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 Figure 6. Drift Bottle Cruise April 16-21, 1975. Open circles indicate
 release stations; solid circles indicate release stations from which bottles
 were recovered; arrows indicate probable drift direction and area of recovery.
                                                10

                                                        influence of the Shoals area appears
Discussion                                              especially pronounced during September
                                                        (Fig. 7), when the southerly counter
     The relatively short duration between              current dominates the inshore water circu-
release and recovery (1-134 days) of                    lation. Card returns from September
bottles during this study suggests trans-               releases suggest that the southerly surface
portation by shelf waters inshore of the                water movements may initiate just south of
influence of the Florida Current. Complete              Cape Fear and dissipate north of Cape
lack of returns within a short periodindi-              Canaveral. Atkinson and Jaffe (In Press)
cates entrainment of bottles and surface                have demonstrated the relationship between
waters by the northerly current and removal             the presence of a strong geostrophic force
from the nearshore system or, less likely,              and the strong southerly drift observed
total loss of bottles stranded in marsh-                inshore during September in this study and
lands along the coast. Bumpus (1955)                    previously by Bumpus (1955) and Bumpus and
reported returns from bottles transported               Chase (1964). Bumpus (1973) states that
from waters off North Carolina by the Gulf              the highly variable nature of the surface
Stream ranging from 218 days (from the                  drift in the South Atlantic Bight is due
Azores) to 891 days (from England). During              to the interplay of a geostrophic current
all months except September 1975, recovery              with southerly influence and the Florida
of bottles suggests a sharp boundary                    Current with northerly influence.
between the waters of the Florida Current
and inner shelf. Several returns from                        Limited returns during November,
releases in September 1975 in or at the                 January and April appear to indicate a
edge of the influence of the Florida Cur-               weak northerly surface water movement
rent were recovered at much later dates                 nearshore, especially in Onslow Bay, and
than releases further inshore and, there-               suggest entrainment of surface waters over
fore, appear to have been temporarily                   most of the shelf with the northerly-
transported within the northerly current                moving Florida Current system. The
prior to release within the southerly                   observed drift directions of bottles
surface system of the inner shelf.                      released south of the Shoals in April con-
                                                        cur with recent findings by Atkinson and
     Inferred water movements indicate the              Jaffe (In Press) for releases south of
importance of Frying Pan Shoals, which ex-              Charleston, South Carolina. We found no
tend almost across the whole shelf, on the              correlation between estimates of monthly
circulation patterns of this area. The                  average Ekman transport values (Gunn, 1976


      ~o              800           790           7r               770                   7r
 3~




 3~                                                                                               3~




 3~                                                                                               3Y



                                                                         lID   ~ 20%   recovery
                                                                         I§§!! ~ 60%   recovery




                                                                                                  32'
                                                  780              770                   760




           Figure   7. The submergedprojectionof Cape Fear, indicatedby the 20 m
           isobath contour and the percent of drift bottle recovery from bottles released
           in September, 1974.
                                             11

and Ingham, 1976) and the direction of
inferred surface water drift. Northerly
returns within Onslow Bay could reflect
slow northerly movement within nearshore
surface waters (Bumpus, 1955; Bumpus and
Lauzier, 1965; and Stefansson, Atkinson
and Bumpus, 1971) or more rapid transport
within the counterclockwise eddy indicated
by results of Stefansson and Atkinson
(1967).

     The average calculated speed for the
northerly surface drift in Onslow Bay
during April (12.7 km/day) was signifi-
cantly greater than that previously
reported by Bumpus (1973) during this time
of year (5.6 to 7.4 km/day). The average
current speeds calculated for northerly
and southerly drift during other months
agree with Bumpus (1973).

     Additional surface and midwater cur-
rent studies are in progress in Onslow Bay
by NMFS at Beaufort, North Carolina and
south of Charleston by Skidaway Institute
of Oceanography and the University of
Miami. These should increase our under-
standing of the circulation patterns over
the continental shelf south of Cape
Hatteras.
                                              12


References
Atkinson, L. P., and L. Jaffe. Drift bot-
     tle returns from four cruises in the
     Georgia Bight and relationship to the
     density and wind field (MS in prepar-
     ation for Tech. Rept. Ser., Ga. }fur.
     Sci. Cent.).

Bumpus, D. F., 1955. The circulation over
     the continental shelf south of Cape
     Hatteras. Trans. Am Geophys. Un.
     36: 601-611.

Bumpus, D. F., 1973. A description of the
     circulation on the continental shelf
     of the east coast of the United
     States. Prog. In Oceanog. 6: 111-157.

Bumpus, D. F. and J. Chase, 1964. Changes
     in the hydrography observed along the
     east coast of the United States.
     I.C.N.A.F. Spec. Pub. 6: 847-854.

Bumpus, D. F. and L. M. Lauzier, 1965.
     Surface circulation on the continental
     shelf off eastern North America be-
     tween Maryland and Florida. Amer.
     Geo. Soc. Ser. Atlas Mar. Envir.
     Folio 7.

Gunn, J. T. 1976. Wind-driven transport
     Atlantic Coast and Gulf of Mexico.
     In: J. R. Goulet, Jr. and E. D.
     Haynes. ed. Status of environment -
     1975 Nat. Mar. Fish. Ser., Wash. Vol.
     2.

Ingham, M. C. 1976. Wind-driven transport
     Atlantic Coast and Gulf of Mexico.
     In: J. R. Goulet, Jr. ed. The envi-
     ronment of the United States Living
     Marine Resources 1974. MARMAP cont.
     No. 104, Nat. Mar. Fish. Ser., Wash.

Norcross, J. J. and E. M. Stanley, 1967.
     Inferred surface and bottom drift,
     June 1963 through October 1964. Cir-
     culation of shelf waters off the
     Chesapeake Bight. Prof. Pap. ESSA
     3(2): 11-42.

Stefansson, U. and L. P. Atkinson, 1967.
     Physical and chemical properties of
     the shelf and slope waters off North
     Carolina. Duke U. Marine Lab. Tech.
     Rept. 230 pp.

Stefansson, U., L. P. Atkinson and D. F.
     Bumpus, 1971. Hydrographic proper-
     ties and circulation of the North
     Carolina shelf and slope waters.
     Deep-Sea Res., 18: 383-420.




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