A general assessment of the Superflux project is made in relation to marine science and oceanography. It is commented that the program clearly demonstrated the effectiveness of state-of-the-art technology required to study highly dynamic estuarine plumes, and the necessity of a broadly interdisciplinary, interactive remote sensing and shipboard program required to significantly advance the understanding of transport processes and impacts of estuarine outflows

Esaias, W. E.

English

NASA Technical Reports Server

ASSESSMENT OF SUPERFLUX 
RELATIVE TO MARINE SCIENCE AND OCEANOGRAPHY 
Wayne E. Esaias 
NASA Langley  Research  Center 
It  is  clearly  much  too  early  in  the  stage of d ta  analysis  to  attempt  a 
real  synthesis  of  results  from  Superflux  with  respect  to  oceanography  and 
marine  science. It is  equally  impractical  to  attempt a synthesis  of  such  a 
diverse  and  complex  program  in  a  short  time.  That  work  will  require  a  great 
deal  of  effort  and  will  result  in  at  least  as  much  information  as  has  already 
been  presented  during  this  symposium.  What  is  clear  is  that  there  are  certain 
threads of scientific  commonality  which  run  through  all  the  presentations  and 
indeed  were  a  result  of  the  design  of  the  Superflux ex iments. 
It  has  been  said  that  if  one  has  no  clear  idea of testable  hypotheses,  no 
clear  idea  of  how  the  data  will  be  used  to  test  those  hypotheses,  and  no  idea 
of  how  the  data  will  look,  then  one  has  no  business  collectir,g  the  data  to 
begin  with.  While  Superflux  may  have  been  somewhat  guilty of this,  the  experi- 
ments  produced  meaningful  and  useful  data  which  would  not  have  been  gathered 
otherwise.  Most  importantly,  showing  that  the  data  could  be  collected,  and 
with  meaningful  results,  is  in  support  of  the  hypothesis  that  interactive  ship, 
aircraft,  and  satellite  measurements  form  a  mutually  exclusive  and  complementary 
data  set,  and  further  that  this  data  set  is  required  to  properly  investigate 
highly  dynamic  coastal  systems. 
In  some  respects  Superflux  did  not  produce  as  complete  a  data  set  as 
would  be  required to attempt  a  flux-type  calculation,  but  this  was  not  an 
expected  accomplishment  for  the  first  year  of  a  study.  We  understand  much  more 
clearly  now  the  small-scale  variances  in  Bay  and  plume  properties  which  need 
to  be  addressed  to  properly  perform  the  rather  herculean  task  of  quantifying 
the  flux of materials,  pollutants,  salt,  water,  carbon,  nitrogen,  etc.,  across 
the  transect  from  Cape  Charles  to  Cape  Henry.  This  information  is  also  essential 
to understand  the  dynamics  of  how  coastal  waters  mix  with  the  waters  of  the  Bay 
and  how  the  plume  affects  the  environment  and  resources  on  the  adjacent  conti- 
nental  shelf. 
The  concept  of  space  and  time  domains  is  important  here.  Referring  to 
figure 1 of  Campbell  et  al.  (ref.  l),  recall  that  synoptic  .aircraft  measure- 
ments  sampled  a  space-time  domain  unapproachable  by  ship  platforms.  Ships 
cannot  cover  enough  distance  in  a  given  time to assess  the  coherence  of  con- 
servative  (passive)  and  non-conservative  (growth-  and  time-dependent)  properties 
over  regions  as  large  as  the  Bay  and  plume.  Shipboard  measurements  can  show 
this  coherence  where  some  relatively  slowly  varying  biological  entities  such 
as  phytoplankton  behave  as  passive  contaminants,  but  only  over  short  times  and 
distances.  References 2 and 3 contain  several  good  examples, 
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This  coherence is readily  apparent on  much  larger  scales of time  and 
space,  such as in the  satellite  imagery  presented in referetices 4 and 5. 
These  images  again  demonstrate  the  existence  of  a  plume,  because  the  data 
were  collected  synoptically.  However,  spatial  resolution  and  time  delays 
inherent in satellite  inagery  do  not  lend  themselves to aiding  real-time 
experiments  by ships,  which  are quired  to  perform  the  complicated  and 
lengthy  physical,  biological,  and  physiological  measurements  to  determine 
how  organisms  are  interacting  with  their  environment. 
Superflux  addressed  the  middle range.of the  space and  time  domain. The 
excellent  shipboard  data  sets  show  that  the  concept  of  a  plume,  really  the 
coherence  of  conservative  and  nonconservative  properties, i  not  apparent in 
the  data.  For some  properties,  however,  this  coherence  is  readily  apparent 
in  the  aircraft  data  sets.  Figure 1 compares  the  microwave  salinity  and  the 
chlorophyll  mappings  of  Kendall  (ref. 6 )  and Hoge (ref. 7) ,  respectively. 
Further  analysis  of  the  data  sets  (cross-correlations,  etc.) will  serve to 
substantiate  the  existence  of  such  a  coherence.  The  major  impact  of  Superflux 
was  the  demonstration,  for  the  first  time,  of  the  ability  to  collect  such 
data  sets  at  subtidal  frequencies.  This  shows  that  many  properties  can  be 
treated  as  passive  contaminants  within  plumes  if  synopticity  is  maintained. 
The  importance  of  vertical  mixing  due  to  tidal  energy in the  plume  area 
and how it  affects  the  distribution  of  properties  is  a  topic  which  has  not 
received  much  attention  in  this  symposium.  Two  facts  can  be  pointed  out 
which  may  be  relevant  as  the  data  are  analyzed  further.  First,  the  dates  of 
the  Superflux  studies  were  biased  toward  spring  tidal  cycles,  or  periods  of 
relatively  high  tidal  energy  dissipation  and  tidal  mixing  (fig. 2 ) .  Secondly, 
the  bathymetry  of  the  adjacent  shelf  is  such  that,  for  reasonable  tidal 
velocities,  the  water  column  should be'well mixed  during  spring  tides  for 
a  considerable  distance  offshore.  The  shelf  break  occurs  approximately  at 
the 50-m  isobath  (fig. 3 ) .  The  ratio  of  water  column  depth  to  the  cube  of 
the  tidal  velocity  amplitude  is  within  the  range  which  indicates  marginal 
stratification  for  much  of  the  shelf.  Thirdly, 1980  was  a  year of  unusually 
low  runoff,  and  added  buoyancy  in  the  form  of  fresh  water  was  at a ten-year 
low  for  the  plume  region. It is  interesting  to  match  a  conceptual  diagram 
of water  column  density  and  other  properties  based  upon  these  facts  (fig. 3)  
with  cross-shelf  distributions  (ref. 2). In  particular,  attention  should  be 
drawn  to  the  band  of  cooler,  clearer  water  seaward  of  the  plume  which  was 
observed  in  several  of  the  remote  sensing  images  and  transects.  This  may 
result  from  tidal  mixing  of  the  water  column  at  this  point,  and  is  a 
hypothesis  to  be  tested  in  the  future. 
In  summary,  the  Superflux  program  clearly  demonstrated  the  effecciveness 
of  state-of-the-art  technology  required  to  study  highly  dynamic  estuarine 
plumes,  and  the  necessity  of  a  broadly  interdisciplinary,  interactive  remote 
sensing  and  shipboard  program  required  to  significantly  advance  our  under- 
standing  of  transport  processes  and  impacts  of  estuarine  outflows.  The 
scientific  accomplishments  which  have  been  presented  here,  and  those  which 
will  come  from  additional  detailed  analysis,  support  the  conceptual  and 
programmatic  accomplishments  in  the  areas  of  experiment  design  and  planning, 
and  have  paved  the  way  for  future  studies  in  these  and  similiar  areas. 
496 
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REFERENCES 
1. 'Campbell,  Janet W.; Esaias,  Wayne E.;  and Hypes,  Warren:  Superflux I, 11, 
and I11 Experiment  Designs:  Remote  Sensing  Aspects.  Chesapeake  Bay 
Plume  Study - Superflux 1980, NASA  CP-2188, 1981 (Paper  no. 4 of this 
compilation) . 
2. Ruzecki,  Evon P.: Temporal  and  Spatial  Variations of the  Chesapeake  Bay 
Plume.  Chesapeake  Bay  Plume  Study - Superflux  1980,  NASA  CP-2188, 1981 
(Paper  no. 9 of this  compilation). 
3 .  Oertel,  George  F.;  and  Wade,  Terry L.: Characteristics  of  Total  Suspended 
Matter  and  Associated  Hydrocarbon  Concentrations  Adjacent  to  the 
Chesapeake  Bay  Entrance.  Chesapeake  Bay  Plume  Study - Superflux 1980, 
NASA  CP-2188, 1981 (Paper  no. 19 of  this  compilation). 
4 .  Munday,  John  C.,  Jr.;  and  Fedosh,  Michael S.: Chesapeake  Bay  Plume 
Dynamics  from  Landsat.  Chesapeake  Bay  Plume  Study - Superflux  1980, 
NASA  CP-2188, 1981 (Paper  no.  7  of  this  Compilation). 
5. Vukovich,  Fred M.; and  Crissman,  Bobby W.: Monitoring  the  Chesapeake  Bay 
Using  Satellite  Data  for  Superflux 111. Chesapeake  Bay  Plume  Study - 
Superflux  1980,  NASA  CP-2188, 1981 (Paper  no. 8 of this  compilation). 
6. Kendall,  Bruce M.: Remote  Sensing of the  Chesapeake  Bay  Plume  Salinity 
Via  Microwave  Radiometry.  Chesapeake  Bay  Plume  Study - Superflux  1980, 
NASA  CP-2188, 1981 (Paper  no. 10 of  this  compilation). 
7. Hoge,  F. E.; and  Swift,  R.  N.:  Application  of  the  NASA  Airborne 
Oceanographic  Lidar  to  the  Mapping  of  Chlorophyll  and  Other  Organic 
Pigments.  Chesapeake  Bay  Plume  Study - Superflux  1980,  NASA  CP-2188, 
1981 (Paper no; 26  of  this  compilation). 
8. National  Ocean  Survey:  Tidal  Current  Tables 1980. Atlantic  Coast  of 
North  America.  U.S.  Dept. of Commerce,  NOAA,  1979. 
497 
(a) Relative chlorophyll a (from re f .  6 ) .  - 
(b) Salinity (from ref .  7 ) .  
Figure 1.- Simultaneous measurements of relative chlorophyll a fluorescence 
and sa l in i ty  on  June 23, 1980, 
-
498 
1.0 - 
u', 
m/sec 
0.5 - 
t 
Figure 2 . -  Daily averages of tidal current maxima at Chesapeake Bay entrance 
for months of Superflux experiments. Portions of l ines  inked 
heavily are dates of specific NASA overflights, illustrating the 
bias toward periods of strong tidal flow (data from ref .  8 ) .  
JAMES SHELF T R A N S E C T  
Distance, Km 
0 25 50 75 100 I25 
a 1 
10 
al  #) "" 
I 70 
aOt 
M :i 
Figure 3 . -  Profile o f  depth along the James/shelf transect. 
499 


Assessment of Superflux relative to marine science and oceanography

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