GEOPHYSICAL RESEARCH LETTERS, VOL. 38, L21404, doi:10.1029/2011GL049458, 2011
An evaluation of subsidence rates and sea‐level variability
in the northern Gulf of Mexico
Alexander S. Kolker,1 Mead A. Allison,2 and Sultan Hameed3
Received 29 August 2011; revised 10 October 2011; accepted 13 October 2011; published 11 November 2011.
[1] While subsidence is widely recognized as a driver of
geomorphic change in the northern Gulf of Mexico (GOM),
there is considerable disagreement over the rates of
subsidence and the interpreted variability in these rates,
which leads to controversies over the impacts of subsidence
on surface land area change. Here we present a new method
to calculate subsidence rates from the tide gauge record that
is based on an understanding of the meteorological drivers
of inter‐annual sea‐level change. In Grand Isle, LA and
Galveston, TX, we explicitly show that temporal patterns of
subsidence are closely linked t o subsurface fluid
withdrawal and coastal land loss, and suggest changes in
withdrawal rates can both increase and decrease rates of
subsidence and wetland loss. Our results also imply that the
volume of sediment needed to rebuild GOM wetlands may
currently fall within the low end of some restoration
scenarios. Citation: Kolker, A. S., M. A. Allison, and S. Hameed
(2011), An evaluation of subsidence rates and sea‐level variability in
the northern Gulf of Mexico, Geophys. Res. Lett., 38, L21404,
doi:10.1029/2011GL049458.
1. Introduction
[2] While it is widely recognized that subsidence can be a
major driver of land loss [Day et al., 2007; Morton et al.,
2002; Reed, 2002], accurate determinations of subsidence
rates on sedimentary shorelines over decadal and centennial
time scales have largely remained elusive. This results primarily from two factors. First, inter‐annual and decadal
scale variability in sea level is orders of magnitude greater
than long‐term trends [Emery and Aubrey, 1991; Kolker and
Hameed, 2007; Kolker et al., 2009]. Second, a dearth of
stable monuments along many sedimentary shorelines
complicates efforts to directly measure subsidence rates,
which is particularly problematic where subsidence is not
primarily a result of glacial isostatic adjustments (GIA),
which can be modeled [Peltier, 2004]. One area where
subsidence is a societal concern and difficult to measure is
the northern Gulf of Mexico (GOM). In the Mississippi
River Delta (MRD), one of this system’s largest features,
various investigators reported subsidence rates that vary
from <5 to >16 mm yr−1 [Dokka, 2006; Törnqvist et al.,
2008].
1
Louisiana Universities Marine Consortium, Chauvin, Louisiana,
USA.
2
Institute for Geophysics, Jackson School of Geosciences,
University of Texas at Austin, Austin, Texas, USA.
3
Institute of Terrestrial and Planetary Atmospheres, School of
Marine and Atmospheric Sciences, Stony Brook University, Stony
Brook, New York, USA.
Copyright 2011 by the American Geophysical Union.
0094‐8276/11/2011GL049458
[3] Our understanding of the patterns in spatial and temporal variability in subsidence rates in the MRD remains
limited, and this variability makes it difficult to quantify the
role that subsidence has played in coastal change. Thus, it is
not clear how much subsidence has contributed to the loss of
4500 km2 of wetlands in the MRD during the 20th Century,
or the loss of 140 km2 in Galveston Bay between 1952 and
1989‐ though it is suspected to be important in both locations [Day et al., 2007; Reed, 2002; White and Tremblay,
1995]. This is an important research gap as wetland loss
depletes habitat for fisheries [Day et al., 2007], releases
organic carbon to the coastal zone [Bianchi et al., 2011;
Wilson and Allison, 2008], alters the hydrodynamics of
coastal bays [Fitzgerald et al., 2004], and increase the vulnerability of coastal communities to tropical cyclones such
as Hurricane Katrina – an event that cost $80–$150 billion
dollars in damages [Day et al., 2007].
[4] Here we present a new analysis of tide gauge records
from the northern Gulf of Mexico that utilizes an understanding of the dynamical drivers of sea level change [Kolker
and Hameed, 2007; Kolker et al., 2009] to demonstrate that
rates of subsidence in Grand Isle, LA and Galveston, TX are
strongly related to patterns of subsurface fluid withdrawal and
patterns of wetland loss. While this has long been suspected,
we show a close sub‐decadal scale coupling between the
processes, indicating a strong relationship between anthropogenic changes in the subsurface and earth surface changes.
2. Data
[5] We used data from the Permanent Service for Mean
Sea Level (PSMSL) for three tide gauges from the northern
GOM, Pensacola, FL; Grand Isle, LA and Galveston, TX
[Woodworth and Player, 2003]. These were chosen to be
representative of different depositional environments with
well‐studied histories of wetland loss and fluid withdrawal
within a similar climatic region (Figures 1 and 2). These
gauges are stationed away from the mouth of the Mississippi
River, and are not likely to be influenced by changes in
stage in the continent’s largest river. They are also among
the longest continually running tide gauges in the northern
GOM for which data is available and standardized by the
PSMSL, thereby facilitating inter‐gauge comparisons. The
Pensacola, FL tide gauge sits on a carbonate platform on
the stable North American continent [Gonzalez and Tornqvist,
2006; Peltier, 2004], thereby providing a record that consists
mostly of the oceanographic and atmospheric drivers of relative sea‐level rise (RSLR), with minimal (<0.5 mm yr–1)
contributions from GIA [Gonzalez and Tornqvist, 2006;
Peltier, 2004]. The Grand Isle, LA tide gauge sits atop a
barrier island at the southern edge of the Barataria Bay, one of
the large interdistributary bays in the MRD. This gauge
L21404
1 of 6
L21404
KOLKER ET AL.: SUBSIDENCE AND SEA LEVEL VARIABILITY
Figure 1. The northern Gulf of Mexico. Image source:
http://www.ngdc.noaa.gov/mgg/shorelines/shorelines.html.
provides a record of RSLR in a sedimentary environment with
extensive human impacts in a region that has experienced
extensive wetland loss. The Galveston, TX Pier 21 gauge is
located in Galveston Bay, TX, a back‐barrier coastal lagoon,
and is also a sedimentary environment that has experienced
considerable human impacts and wetland loss in the past
century [White and Tremblay, 1995].
3. Results and Discussion
3.1. Sea Level Variability and Trends
[6] The long‐term linear rate of RSLR was 2.15 ± 0.15 mm
yr−1 at Pensacola, 6.38 ± 0.16 at Galveston and 9.27 ± 0.34 mm
L21404
yr−1 at Grand Isle (Table 1 and Figure 2a). Despite these
differences in trends, the year‐to‐year sea level variability at
these stations was similar. To demonstrate this, we removed
the linear trend, which is a combination of subsidence, isostacy, eustacy and long‐term dynamical shifts, and plotted
the three gauges against each other (Figure 2b). A linear,
least squares fit indicates that the variance in the detrended
Pensacola tide gauge can explain 61% of the variance in the
detrended Grand Isle and Galveston gauges, while a linear
model of the variance in the Galveston tide gauge can
explain 82% of the variance in the Grand Isle tide gauge.
Because these gauges are highly correlated, the drivers of
inter‐annual variability are likely to be similar [Kolker and
Hameed, 2007; Kolker et al., 2009].
3.2. Atmospheric Drivers of Interannual Sea Level
Change
[7] To understand the drivers of this inter‐annual variability, we examined wind velocity, atmospheric pressure at
sea level, and skin (i.e., sea) surface temperature (SST)
anomalies (Figure 3), during years in which sea level at the
geologically stable Pensacola gauge was 1s above the mean
and 1 s below the mean, using the NCEP/NCAR reanalysis
tool [Kalnay et al., 1996]. These anomalies are relative to
the period 1981–2010, a procedure that follows earlier work
[Kolker and Hameed, 2007; Kolker et al., 2009; Piontkovski
and Hameed, 2002]. During years in which detrended sea
Figure 2. (a) The raw tide gauge data for Galveston (black dotted line), Grand Isle (blue line) and Pensacola (green line).
Data source: Permanent Service for Mean Sea Level, http://www.psmsl.org. (b) Detrended RSLR. The statistical relationships between these gauges are reported in the text. The dotted arrows are the years used to determine the climate anomalies
in Figure 3. (c) Inferred subsidence in mm at Grand Isle and Galveston. The regression lines presented are for the time slices
listed in Table 1, i.e., 1947–1958, 1959–1974, etc. (d) Oil production in south Louisiana (solid black line [Meckel, 2008])
and inferred subsidence rate for six‐year periods in mm/year periods at Grand Isle (blue squares, dashed line). (e) Land Loss
in the Barataria Bay (solid black line) vs. inferred subsidence rate at Grand Isle (blue squares, dashed line [Couvillion et al.,
2011]). (f) Water withdrawal in Galveston, TX (black line [Meckel, 2008]), vs. inferred subsidence rate at Galveston, TX
(blue squares, dotted line). The error bars in subsidence rates were determined from the error of a least squares fit of the
regression line, while the errors bars in the time period are simply the age range over which the analyses were conducted.
2 of 6
L21404
KOLKER ET AL.: SUBSIDENCE AND SEA LEVEL VARIABILITY
Table 1. Rates of Relative Sea Level Rise and Inferred Subsidence at Grand Isle, LA and Galveston, TXa
Period
Grand Isle
r2
Galveston
r2
1947–2006 RSL
1947–2006
1947–1958
1959–1991
1959–1974
1975–1991
1992–2006
9.27 ± 0.34
7.59 ± 0.23
3.16 ± 1.00
9.82 ± 0.33
12.64 ± 0.69
8.59 ± 0.75
1.04 ± 0.97
0.93
0.95
0.50
0.97
0.97
0.92
0.10
6.24 ± 0.26
4.722 ± 0.21
2.55 ± 2.17
6.18 ± 0.342
7.14 ± 1.06
7.05 ± 0.87
−1.987 ± 1.41
0.89
0.90
0.12
0.92
0.76
0.82
0.14
a
RSL denotes rates of RSLR as determined from a linear fit of the
Permanent Service for Mean Sea Level data, while all the other rates are
inferred subsidence rates as determined by subtracting the local gauge
from the Pensacola gauge. All rates are statistically significant at the p <
0.01 level or greater unless they are bolded. The r2 value is the amount
of variance explained by a linear fit of the data, be it the relative sea‐
level rise or the inferred subsidence.
level anomalies in Pensacola are high, there is a large low
atmospheric pressure anomaly over the western United
States and wster GOM, which contributes to a wind
anomaly directing water towards the northern GOM. These
are also years with SST anomalies of 0.2 ∼ 0.3oC. During
years with low sea levels at Pensacola the opposite pattern
emerges. Sea level pressures are high over the western and
northern GOM, wind anomalies are pointed away from the
northern Gulf with a limited rotation, and there is a 0.0 to
−0.1oC SST anomaly. Most likely, the differences between
high and low periods can be explained by shifts in atmospheric pressure, which control wind fields that drive water
on or offshore. In years of high pressure, this results in warm
water transport from the southern GOM towards the northern GOM. In years of low sea level, northern GOM waters
are blown southward, potentially leading to upwelling of
colder deeper waters.
3.3. Determination of Subsidence Rates
[8] If we are correct that the interannual variability observed
in Figure 2b results from the meteorological factors presented
in Figure 3, then we can remove the correlated interannual
variability and isolate subsidence rates at each gauge by
subtracting the Pensacola record from Grand Isle and Galveston gauges. Since Pensacola sits on a stable carbonate
platform where vertical land movements are minimal, these
new records provide estimates of subsidence at Grand Isle and
Galveston. The long‐term rate of subsidence for Grand Isle
and Galveston were determined to be 7.59 ± 0.23 mm yr−1
and 4.71 ± 0.21 mm/yr respectively. These new subsidence
records can be viewed in a number of different ways. The
inferred Grand Isle subsidence curve appears to experience
three distinct phases. Phase 1 lasts from 1948 to 1958 and
has a trend of 3.16 ± 1.0 mm yr−1. Phase 2 lasts from 1958
to 1991, and has a trend of 9.82 ± 0.33 mm yr−1, while phase 3
lasts from 1992–2006 and has a rate of 1.04 ± 0.97 mm yr−1.
Galveston too can be broken into three similar sections with
rates that are 2.55 mm yr−1 ± 2.15 for 1947–1958, 6.18 ±
0.34 mm yr−1 for 1959–1991 and −1.99 ± 1.41 mm yr−1 for
1992–2006.
[9] Alternatively one can calculate subsidence rates for
successive 6‐year periods. This interval is a practical consideration that is long enough to reduce biases related to the
remaining inter‐annual variability and short enough to allow
one to see changes in subsidence rates over time (Figures 2d
and 2e). Since 6 is a multiple of 18, this approach partially
L21404
allows us to account for the 18.6 lunar nodal cycle [Gratiot
et al., 2008]. Rates of subsidence in Grand Isle follow a
quasi‐parabolic pattern. They start at 3.52 ± 2.79 mm yr−1
in the 1947–1952 period, reach their maximum of 15.83 ±
3.06 mm yr−1 in the 1965–1970 period and then decline to
−1.54 ± 6.20 mm yr−1 in the 2001–2006 period. In Galveston, the inferred pattern of subsidence is more erratic, particularly if pre‐1947 rates are included. Inferred rates of
subsidence range from +13.62 mm/yr from 1925–1930 to
−12.93 ± 7.08 mm yr−1 for the period 2001–2006 (Figure 2f).
Like Grand Isle, there is a steady decline in rates of subsidence after the mid‐1970s. Both analyses yield negative rates
of subsidence at Galveston, which probably results from
differences in dynamically driven sea level changes between
Galveston and Pensacola [Kolker and Hameed, 2007], resulting from the differences in atmospheric pressure, wind
and SST anomalies between these sites (Figure 3).
[10] These rates can be compared to published rates of
subsidence and relative sea level change. A study of a relict
swamp in south Louisiana suggests that subsidence in the
MRD is driven largely by compaction of peat layers, indicating subsidence rates that are typically <5 mm yr−1
[Törnqvist et al., 2008]. An alternative view, based on releveling surveys, suggests that rates in eastern New Orleans
were as high as 16.9 mm yr−1, at least for short intervals of
time [Dokka, 2006]. Our results essentially suggest that both
authors have valid points – subsidence before oil and gas
withdrawal accelerated were close to the Törnqvist et al.
[2008] rates while rates observed during the period of
maximum fluid withdrawal were closer to Dokka’s [2006]
higher rates. The patterns in subsidence we observe in
Grand Isle are similar to Morton and Bernier’s [2010] tide
gauge analysis, which indicated that rates of RSLR rates in
the MRD varied over the past century, with the greatest rates
(10.3 mm yr−1) occurring between 1965–1993, and slower
rates occurring before (3.3 mm yr−1; 1947–1965) and after
(4.1 mm yr −1 ; 1993–2006). While Morton and Bernier
[2010] were unable to account for the effects of eustacy
and inter‐annual variability on RSLR trends, our results
corroborate their analyses, and advance on their work by
removing the oceanographic and atmospheric‐derived variability processes, thereby highlighting the impacts of subsidence on relative sea level trends in the northern GOM.
3.4. Drivers of Subsidence
[11] One likely driver of subsidence in the northern GOM
is subsurface fluid withdrawal, which can drive subsidence
by decreasing the pressure associated with these fluids,
thereby altering grain‐to‐grain contacts in the sediments
[Holzer and Galloway, 2005; Mallman and Zoback, 2007;
Morton et al., 2002; Morton and Bernier, 2010]. Onshore
oil production in south Louisiana stood at 1.14 × 108 barrels
in 1945, reached a maximum of 4.37 × 108 barrels in 1968
and declined to 5.55 × 107 barrels in 2005 [Meckel, 2008].
Interestingly, this pattern in oil production shows a close
correspondence to changes in subsidence rates (Figure 2e),
suggesting an increase in subsidence as production
increased and a decrease in subsidence as production slowed
down. At Galveston, where subsidence is generally recognized to be influenced by groundwater withdrawal [White
and Tremblay, 1995; White and Mortan, 1997], a similar
phenomenon emerges (Figure 2f). Calculated rates of subsidence are greatest during the early‐mid 20th century when
3 of 6
Figure 3. Climate anomalies during periods of (top) high, and (bottom) low sea level at Pensacola. (left) The atmospheric pressure anomaly, (middle) the wind anomaly and (right) the sea surface temperature anomaly. The arrows
are a dimensionless direction, while the magnitude of the velocity is color coded. Image source: NOAA/ESRL Physical
Sciences Division, Boulder Colorado via their Web site at http://www.esrl.noaa.gov/psd/.
L21404
KOLKER ET AL.: SUBSIDENCE AND SEA LEVEL VARIABILITY
4 of 6
L21404
L21404
KOLKER ET AL.: SUBSIDENCE AND SEA LEVEL VARIABILITY
rates of fluid withdrawal were greatest and decline after the
mid‐1970s as groundwater withdrawals decreased [Meckel,
2008]. We therefore link changes in subsidence to human
activity, and suggest that changes in subsidence rates can be
brought about by changes in the volume of fluid removed
from reservoirs or aquifers. While others have noted this
before [Morton et al., 2002], our analysis suggests a tight
temporal coupling between the two, indicating that subsurface anthropogenic activities can have a rapid influence on
earth surface processes.
[12] It is likely that these trends are not artifacts of the
methods used or contaminated by broader‐scale processes.
If the changes observed were caused by the establishment of
the tide gauge monument, then the rate of subsidence would
be greatest at the beginning of the record and should
decelerate thereafter, which is not observed here. The differences in subsidence rates calculated are also unlikely to
be a function of the measurement length [Meckel, 2008;
Sadler, 1981], as the gauges can all be broken into time
slices of similar lengths. These changes are unlikely to be a
function of global sea level rise‐ as those would be a) accounted for in the Pensacola gauge a b) should show an
acceleration after ∼1993 [Merrifield et al., 2009], rather than
a deceleration. GIA rates along the northern GOM range
between 0.1 to 0.2 mm yr−1 [Peltier, 2004], which is one to
two orders of magnitude less than the rates of subsidence
calculated here. Changes in subsidence rates due to the
loading of sediments along the Mississippi River valley
[Blum et al., 2008], are also unlikely to be important on the
temporal scale measured here.
[13] In the northern GOM there are numerous faults,
which some authors have suggested are partially responsible for land loss [Dokka, 2006; White and Tremblay, 1995].
For example, Dokka [2006] suggested that the Michaud
fault in eastern New Orleans experienced a substantial slip
of 16.9 mm yr−1 from 1969–1971, which was followed by
a period of relatively rapid subsidence (7.1 mm yr−1 from
1971–1977), and then a quasi‐asymptotic deceleration until
the early 1990s. While there are some similarities between
the rates we report and Dokka’s [2006] rates, our subsidence curve suggests relatively systematic changes for over
fifteen years (1959–1974), which are unlikely to be caused
by a slip event. In Galveston, faulting appeared to be most
active in the 1960s and 1970s, which was a period of high
but variable subsidence, suggesting that slippage may have
played a more important role here.
3.5. Influence of Subsidence on Land Loss
[14] To understand the implications of subsidence on
coastal processes, we compared subsidence rates at Grand
Isle, LA to measurements of persistent land loss in Barataria
Bay (Figure 2e) [Couvillion et al., 2011]. The definition of
persistent land loss is derived from an algorithm that looks
for land loss that is observable from maps and aerial photographs over multiple time periods, and as such, is relatively free from the influence of local water level changes
[Couvillion et al., 2011]. Land loss was relatively slow
during the period 1932–1956 (6.1 km2 yr−1; 146 km total),
reached a maximum during the period 1973–1975 (92.4 km2
yr−1; 166 km2 total) and then generally declined, reaching a
total of 9.3 km2 yr−1 from 2008–2010 [Couvillion et al.,
2011]. While there are almost certainly spatial variations
in subsidence rates, similar patterns emerge when one
L21404
compares rates of subsidence in Grand Isle to rates of land
loss across the entire MRD [Couvillion et al., 2011]. Galveston Bay is also an area that has experienced rapid wetland loss that has been linked to subsidence. Though
temporal patterns in wetland loss in Galveston have not be
quantified as precisely as in Louisiana, spatial patterns in
subsidence across Galveston Bay tend to match the spatial
patterns in wetland loss [White and Tremblay, 1995].
[15] Taken together, these findings point to a tight coupling between fluid withdrawal, subsidence rates, and wetland loss. Subsidence, coupled with reduced sediment loads
and global sea level rise, leads to an elevation deficit,
leading to marsh submergence of marshes and conversion of
land into open water [Day et al., 2007; Morton et al., 2002;
Reed, 2002; Roberts, 1997]. Similar processes appear to be
operating in the MRD and GB, despite different types of
fluid withdrawal [Meckel, 2008; Morton and Bernier, 2010;
White and Tremblay, 1995; White and Mortan, 1997]. It
should be noted that subsidence is not the only process
driving land loss in the MRD, GB or elsewhere. Surface
processes including canal construction, sediment compaction saltwater intrusion, reduced sediment loads, changing
biogeochemical regimes and invasive species have all
played an important role in coastal land loss [Day et al.,
2007; Gagliano et al., 1981; Meckel et al., 2006;
Törnqvist et al., 2008; Turner, 1997]. However, subsidence
can make coastal wetlands more vulnerable to surface impacts, as it lowers the elevation of wetlands to a point that is
outside of the range of tolerances for vegetation, increases
the amount of material needed for marsh surfaces to maintain an elevation equilibrium with sea level, and increases
the amount of open water in a bay, which increases fetch
and erosive processes [Reed, 2002].
3.6. Implications for Coastal Restoration
[16] Our work has important implications for the restoration the MRD and other coastal systems, as the subsidence
rate is a key variable entered into calculations of coastal
sustainability [Reed, 2002]. We suggest that subsidence can
be exacerbated or mitigated by anthropogenic activities on
sub‐decadal time scales. These results are limited in spatial
extent, and do not cover the Bird’s Foot region of the MRD
where subsidence rates are greatest and linked to the thickness
of Holocene sediments. These findings can also be compared
to projections of land change in the MRD. One recent study
modeled the survivability of the MRD, using subsidence rates
that ranged from 3–8 mm yr−1 [Blum and Roberts, 2009], and
concluded that large areas of the MRD would drown under
high rates of subsidence and global sea‐level rise. However
that report also suggested that with low rates of subsidence
and global sea level rise, coupled with high rates of sediment
trapping, net accretion could occur [Blum and Roberts, 2009].
The subsidence rates we calculated for Grand Isle are presently lower than Blum and Roberts’ low‐end subsidence
scenario, though they once exceeded their high‐end scenario.
If these findings are confirmed by future studies conducted
across wider areas, future wetland losses associated with
subsidence could be limited.
[17] Acknowledgments. We thank K. Straub, K. Williams and
N. Gasparini for a productive conversation that helped kick‐off this work.
We thank T. Meckel for providing the estimates of oil production in coastal
Louisiana and water withdrawal in Galveston Bay that were originally
5 of 6
L21404
KOLKER ET AL.: SUBSIDENCE AND SEA LEVEL VARIABILITY
presented by Meckel [2008]. R. Morton helped provide background information on subsidence in Galveston Bay. T. Meckel and S. Bentley provided
thoughtful reviews which improved the paper.
[18] The Editor thanks Sam Bentley and Timothy Meckel for their
assistance in evaluating this paper.
References
Bianchi, T. S., et al. (2011), Sources of terrestrial organic carbon in the
Mississippi River plume region: Evidence for the importance of coastal
marsh inputs, Aquat. Geochem., 17, 431–456, doi:10.1007/s10498-0109110-3.
Blum, M. D., and H. H. Roberts (2009), Drowning of the Mississippi
Delta due to insufficient sediment supply and global sea level rise,
Nature Geoscience, 2(7), pp. 488–491.
Blum, M. D., et al. (2008), Ups and downs of the Mississippi Delta,
Geology, 36(9), 675–678, doi:10.1130/G24728A.1.
Couvillion, B. R., et al. (2011), Land change in coastal Louisiana from
1932 to 2010, scale 1:265,000, U.S. Geol. Surv. Sci. Invest. Map,
3164, 12 pp.
Day, J. W., et al. (2007), Restoration of the Mississippi Delta: Lessons from
Hurricanes Katrina and Rita, Science, 315(5819), 1679–1684,
doi:10.1126/science.1137030.
Dokka, R. K. (2006), Modern‐day tectonic subsidence in coastal Louisiana,
Geology, 34(4), 281–284, doi:10.1130/G22264.1.
Emery, K. O., and D. G. Aubrey (1991), Sea Levels, Land Levels and Tide
Gauges, 239 pp., Springer, New York.
Fitzgerald, D. M., et al. (2004), Morphologic and stratigraphic evolution of
muddy ebb‐tidal deltas along a subsiding coast: Barataria Bay, Mississippi River Delta, Sedimentology, 51(6), 1157–1178, doi:10.1111/
j.1365-3091.2004.00663.x.
Gagliano, S. M., et al. (1981), Land loss in the Mississippi River deltaic
plan, Trans. Gulf Coast Assoc. Geol. Soc., 31, 295–300.
Gonzalez, J. L., and T. E. Tornqvist (2006), Coastal Louisiana in crisis:
Subsidence or sea level rise, Eos Trans. AGU, 87(45), 493,
doi:10.1029/2006EO450001.
Gratiot, N., et al. (2008), Significant contribution of the 18.6 year tidal
cycle to regional coastal changes, Nat. Geosci., 1(3), 169–172,
doi:10.1038/ngeo127.
Holzer, T. L., and D. L. Galloway (2005), Impacts of land subsidence
caused by withdrawal of underground fluids in the United States, in
Humans as Geologic Agents, edited by J. Ehlen et al., pp. 87–99, Geol.
Soc. of Am., Boulder, Colo., doi:10.1130/2005.4016(08).
Kalnay, E. M., et al. (1996), The NCEP/NCAR 40 year reanalysis project,
Bull. Am. Meteorol. Soc., 77, 437–471, doi:10.1175/1520-0477(1996)
077<0437:TNYRP>2.0.CO;2.
Kolker, A. S., and S. Hameed (2007), Meteorologically driven trends in sea
level rise, Geophys. Res. Lett., 34, L23616, doi:10.1029/2007GL031814.
Kolker, A. S., et al. (2009), High resolution records of coastal systems
responses to short‐term sea‐level variability, Estuarine Coastal Shelf
Sci., 84(4), 493–508, doi:10.1016/j.ecss.2009.06.030.
Mallman, E. P., and M. D. Zoback (2007), Subsidence in the Louisiana
coastal zone due to hydrocarbon production, J. Coastal Res., 50, 443–448.
L21404
Meckel, T. A. (2008), An attempt to reconcile subsidence rates determined
from various techniques in southern Louisiana, Quat. Sci. Rev., 27,
1517–1522, doi:10.1016/j.quascirev.2008.04.013.
Meckel, T. A., U. S. ten Brink, and S. J. Williams (2006), Current subsidence rates due to compaction of Holocene sediments in southern Louisiana,
Geophys. Res. Lett., 33, L11403, doi:10.1029/2006GL026300.
Merrifield, M. A., et al. (2009), An anomalous recent acceleration of global
sea level rise, J. Clim., 22(21), 5772–5781, doi:10.1175/
2009JCLI2985.1.
Morton, R. A., and J. C. Bernier (2010), Recent subsidence‐rate reductions
in the Mississippi Delta and their geological implications, J. Coastal
Res., 26(3), 555–561, doi:10.2112/JCOASTRES-D-09-00014R1.1.
Morton, R. A., et al. (2002), Subsurface controls on historical subsidence
rates and associated wetland loss in southcentral Louisiana, Trans. Gulf
Coast Assoc. Geol. Soc., 52, 767–778.
Peltier, W. R. (2004), Global glacial isostasy and the surface of the Ice‐Age
Earth: The ICE‐5G (VM2) Model and GRACE, Annu. Rev. Earth
Planet. Sci., 32, 111–149, doi:10.1146/annurev.earth.32.082503.144359.
Piontkovski, S., and S. Hameed (2002), Precursors of copepod abundance
in the Gulf of Maine in atmospheric centers of action and sea surface
temperature, Global Atmos. Ocean Syst., 8, 283–291, doi:10.1080/
10236730290030932.
Reed, D. J. (2002), Sea‐level rise and coastal marsh sustainability: Geological and ecological factors in the Mississippi delta plain, Geomorphology,
48, 233–243, doi:10.1016/S0169-555X(02)00183-6.
Roberts, H. H. (1997), Dynamic changes of the Holocene Mississippi River
delta plain: The delta cycle, J. Coastal Res., 13(3), 605–627.
Sadler, P. M. (1981), Sediment accumulation rates and the completeness of
the stratigraphic record, J. Geol., 89(5), 569–584, doi:10.1086/628623.
Törnqvist, T. E., et al. (2008), Mississippi Delta subsidence primarily
caused by compaction of Holocene strata, Nat. Geosci., 1(3), 173–176,
doi:10.1038/ngeo129.
Turner, R. E. (1997), Wetland loss in the northern Gulf of Mexico: Multiple
working hypotheses, Estuaries, 20(1), 1–13, doi:10.2307/1352716.
White, W. A., and R. A. Mortan (1997), Wetland losses related to fault
movement and hydrocarbon production, southeastern Texas coast,
J. Coastal Res., 13(4), 1305–1320.
White, W. A., and T. A. Tremblay (1995), Submergence of wetlands as a
result of human‐induced subsidence and faulting along the upper Texas
Gulf Coast, J. Coastal Res., 11(3), 788–807.
Wilson, C. A., and M. A. Allison (2008), An equilibrium profile model for
retreating marsh shorelines in southeast Louisiana, Estuarine Coastal
Shelf Sci., 80(4), 483–494, doi:10.1016/j.ecss.2008.09.004.
Woodworth, P. L., and R. Player (2003), The permanent service for mean sea
level: An update for the 21st century, J. Coastal Res., 19(2), 287–295.
M. A. Allison, Institute for Geophysics, Jackson School of Geosciences,
University of Texas at Austin, Austin, TX 78758, USA.
S. Hameed, Institute of Terrestrial and Planetary Atmospheres, School of
Marine and Atmospheric Sciences, Stony Brook University, Stony Brook,
NY 11794, USA.
A. S. Kolker, Louisiana Universities Marine Consortium, 8124 Hwy. 56,
Chauvin, LA 70344, USA. ([email protected])
6 of 6