Circulation in a Complex Estuarine Environment

1
Circulation in a Complex Estuarine Environment
Elias J. Hunter, Robert Chant, Richard
Styles, Scott Glenn, Kelly Rankin, Michael S.
Bruno Inst. Of Marine and Coastal Sciences,
Rutgers University, New Brunswick, N.J.
University of South Carolina Stevens Institute
Of Technology, Hoboken, N.J. http//marine.rutgers
.edu/cool/coolresults/agu2002
Tidal Variability
Sediment Transport
Meteorological forcing is most apparent in the
depth averaged flows in the Kill van Kull (red
line) and Arthur Kill (blue line).In figure 9 the
upper panel compares subtidal flows to the E/W
wind, while the lower panel compares these
currents to sea-level. Qualitatively, it appears
that the subtidal flows in the Kills is primarily
driven by local winds.
Introduction
Spring Tide Low River Discharge
NB1
Optical backscatter, a surrogate for sediment
oncentration, is highly variable. A connection to
tidal variation is apparent. Examples are given
in figures 12-14.
The New Jersey Department of Environmental
Protection, as part of The Toxics Reduction
Program, supports ongoing hydrographic surveys of
the Newark Bay estuarine system. A detailed
description of dynamic processes in the region
provides a framework for interpreting chemical
data in and around Newark Bay. Contaminants tend
to be bound to fine grain sediments that are
resuspended and transported by currents. While a
numerical model will ultimately be needed to make
detailed predictions on the transport and fate of
contaminants, analysis of the hydrographic data
is needed to tune and assess the skill of
numerical simulations of this system. In this
study, data collected from moored instruments are
used to characterize fluid motion in terms of
forcing parameters such as tides, buoyancy, and
m

• Tidal Currents are strongest at the Kill van Kull
  mooring and weakest at the Newark Bay mooring.
• The largest salinity fluctuations occur at NB1,
  suggestive of a strong horizontal salinity
  gradient.
• Ebbing currents (blue) are surface intensified,
  while flooding currents (red) exhibit a mid-depth
  maximum at NB1 and KVK.

KVK
m

• OBS values are generally maximum at flood tide
  during the March KVK deployment. (figure 12)
• OBS flux during March is directed into Newark Bay.

PA
m
Figure 2
0m - bottom

• Vertical shear of the tidal amplitude is weak and
  the tidal currents turn in unison from surface to
  bottom.

meteorology. Since the Newark Bay system has
received little attention, particularly compared
to the near by Hudson and Long Island Sound we
begin our study with a basic description of
easily observed estuarine processes in this
complex system.

• OBS values are generally maximum at ebb tide
  during the April KVK deployment. (figure 13)
• OBS flux during April is directed out of Newark
  Bay.

• Data used in this poster was primarily obtained
  from the following mooring locations marked
  above
• Perth Amboy (PA) during March 2001 April 2001
• Newark Bay 1 (NB) during Dec 2000, March 2001
  April 2001
• Arthur Kill (AK) during Dec 2000
• Kill Van Kull (KVK) during Dec 2000 March
  2001

• The data also indicates that there are two modes
  of subtidal flows in the Kills. The first mode is
  characterized by a flow through mode and the
  second by an emptying/filling mode. Figures 10
  and 11 below show examples of these modes.
• On day 63 (figure 10) the flow through mode is
  evident. A strong easterly wind set up coastal
  sea-level and the fluid in the kills flows
  clockwise around Staten Island.
• On day 81 (figure 11) the filling/emptying mode
  is evident. Fluid leaves Newark Bay through both
  the Arthur Kill and the Kill van Kull.

Forcing Parameters
Sub Tidal Variability
While sub tidal (lower frequency) current speeds
are significantly weaker than tidal current,
they may dominate transport processes at time
scales longer than 1-day due to their
persistence. The panels below show the
non-tidal flows at the three mooring deployments
from March 2001. There is a persistent 2-layer
flow at NB1, a weak 2-layer flow at KVK and a
variable two-layer flow at PA. The subtidal
flows at NB1 are primarily associated with
density driven forces. The variability in
subtidal motion appears to be associated with
meteorological forcing.
A 30 day deployment in March 2001 captured the
changing character of tidal motion in response to
changes in tidal range and river discharge.
Figure 1 below shows river discharge, tidal
range, tidal fluctuations, and low frequency sea
level. The low passed sea-level is indicative of
wind forcing. Storms are associated with times of
high sea-level (Day 66,80,89) Three 2-day
periods (marked in red) represent various forcing
regimes including spring tide-low river discharge
(day 66-68), neap-tide-high river discharge (day
77-79), and spring tide-high river discharge (day
87-89).

• OBS values are generally maximum at flood tide
  during the April NB1 deployment. (figure 14)
• OBS flux during April is directed north.

Conclusions
High Discharge

• 1) The nature of tidal and subtidal motion in the
  Newark Bay system is typical of that found in
  many other estuarine systems.
• The tidal period motion in this system exhibits
  significant spring-neap variability. This
  variability is most pronounced at Perth Amboy and
  least pronounced in the Kill van Kull.
• Two layer estuarine circulation is most
  pronounced in Newark Bay, weakest in the Kill van
  Kull and most variable at the Perth Amboy
  mooring. The variability is, in part, due to the
  meteorological forcing.
• Meteorological forced flows in the Kills are
  composed of two modes, one characterized by a
  simple emptying/filling and the second by a flow
  through mode. Details of the mechanics driving
  these flows and the relative importance of each
  remains undetermined.
• Moored data suggests that sediment transport at
  the head of Newark Bay is directed northward. In
  the Kill Van Kull there three of four mooring
  deployments
• 2) Indicate a transport into Newark Bay, while
  the April deployment indicated a transport out of
  Newark Bay. Upcoming studies will estimate
  sediment flux more quantitatively, and include
  processes associated with vertical and lateral
  variability.

Low Discharge
Storms



Spring Tide
Neap Tide
Acknowledgements Funding for this study was
provide by the New Jersey Department of
Environmental Protection
Figure 11
Figure 10
FIGURE 1