Tidal Phase Research Articles

Temporal variation of the underwater soundscape in Jiaotou Bay, an Indo-Pacific humpback dolphin (Sousa chinensis) habitat off Hainan Island, China.

The underwater soundscape is an important ecological element affecting numerous aquatic animals, in particular dolphins, which must identify salient cues from ambient ocean noise. In this study, temporal variations in the soundscape of Jiaotou Bay were monitored from February 2016 to January 2017, where a population of Indo-Pacific humpback dolphins (Sousa chinensis) has recently been a regular sighting. An autonomous acoustic recorder was deployed in shallow waters, and 1/3-octave band sound pressure levels (SPLs) were calculated with central frequencies ranging from 25 Hz to 40 kHz, then were grouped into 3 subdivided bands via cluster analysis. SPLs at each major band showed significant differences on a diel, fishing-related period, seasonal, and tidal phase scale. Anthropogenic noise generated by passing ships and underwater explosions were recorded in the study area. The fish and dolphin acoustic activities both exhibited diel and seasonal variations, but no tidal cycle patterns. A negative significant relationship between anthropogenic sound detection rates and dolphin detection rates were observed, and fish detection rates showed no effect on dolphin detection rates, indicating anthropogenic activity avoidance and no forced foraging in dolphins in the study area. The results provide fundamental insight into the acoustic dynamics of an important Indo-Pacific humpback dolphin habitat within a coastal area affected by a rapid increase in human activity, and demonstrate the need to protect animal habitat from anthropogenic noises.

Aerosols and Tides in the Martian Tropics During Southern Hemisphere Spring Equinox From Mars Climate Sounder Data

AbstractWe analyze Mars Climate Sounder temperature and aerosol data in the tropics, and use Fourier analysis at different local times to study atmospheric tides and their relation to the dust and water ice distributions. Our results reveal that Mars year (MY) 29 has large amplitude non‐migrating thermal tides during southern hemisphere spring equinox that are not observed at the same local time in any other year. The nighttime temperatures are the most perturbed compared to other years, with strong temperature inversions at 35–55 km altitude. The nighttime water ice cloud structure is strongly influenced by the eastward‐propagating diurnal Kelvin waves 1 and 2. Increased nighttime radiative cooling from regions of thicker clouds results in stronger downwelling above the clouds, leading to increased adiabatic warming and a strengthening of the temperature inversions. The temperatures and water ice clouds at 3:45 a.m. in MY29 more closely resemble those at 5:00 a.m. in other years, suggesting there was a shift in the phase of the diurnal tide. This phase shift, and the large amplitude non‐migrating thermal tides, appear to be related to early dust activity. Two early dust storms occurred in MY29 around the time there was upwelling over the tropics, associated with the Hadley circulation. This likely enabled the dust to be transported to higher altitudes where it has a larger radiative influence. The early dust activity in MY29 also increased the strength of the westward‐propagating non‐migrating thermal tides.

Abnormal Phase Structure of Thermal Tides During Major Dust Storms on Mars: Implications for the Excitation Source of High‐altitude Water Ice Clouds

AbstractInteractions among the thermal tide, airborne dust, and water ice clouds significantly influence the Martian atmosphere. The absence of a stratosphere on Mars allows easier identification of the thermal tides from observational data than that on Earth, making Mars a natural laboratory to study the tidal excitation and propagation processes. However, the global tidal phase structure and its response to the tidal excitation sources on Mars have not been studied from observations. Here, we present a comprehensive analysis of the phase structure of migrating diurnal tide (DW1) using multi‐local‐time observations of the Mars Climate Sounder. The DW1 phase at low‐to‐mid latitudes shows a downward phase progression, which indicates upward tidal energy and momentum propagation throughout the year but with an apparent hemispheric asymmetry. The entire DW1 phase structure rises and falls with the dust height at the southern mid‐latitudes suggesting a modulation of vertical dust extent on the altitude of the excitation source. During major regional dust storms, the DW1 phase propagates anomalously upward from 10 to 1 Pa in the Southern hemisphere. The Hough analysis suggests that the DW1 in the dust layer can only propagate upward to 10 Pa while the downward propagating mode above 10 Pa may be excited from a high‐altitude source. Evidence suggests that the enhanced high‐altitude water ice clouds could be a potential excitation source for these downward propagating tidal modes. These findings demonstrate how thermal tides can locally behave like inertia‐gravity waves and the importance of water ice clouds to Martian atmospheric dynamics.

Characterising industrial thermal plumes in coastal regions using 3-D numerical simulations

Coastal power stations use sea water as a coolant, releasing it back into coastal environments at a higher-than-ambient temperature. Due to the possible ecological impacts on sensitive coastal zones, thermal plume formed by warmer coolant waters needs to be monitored, which is typically done through field campaigns. This paper assesses the use of simulations and remotely sensed observations as complimentary methods to characterise plume behaviour for a chosen coastal power station located within an inter-tidal embayment. Simulations of the thermal plume for two main tide phases and associated sea current conditions are validated against the high-resolution satellite observations. Simulated plume temperatures are higher than the observed values, with the biggest difference of 2 °C. The direction of the simulated plume dispersion is in agreement with observations and depends on the strength and direction of sea currents associated with the phase of the tide. The plume stretches most at the surface with limited impact on the benthic temperatures.

Ecological scaling in mangroves: The role of microhabitats for the distribution of larval assemblages

Mangroves are regarded as important spawning and settlement grounds as well as nurseries for larvae and juvenile fishes and invertebrates due to the sheltered nature of these ecosystems. The present study examined the spatial and temporal distribution of fish and invertebrate larvae, simultaneously among several microhabitats, within two South African mangrove forests. Results indicate that despite temperature and salinity homogeneity across microhabitats, spatio-temporal differences occurred in both fish and invertebrate larval assemblages. The distinct larval assemblages were driven by the site-specific predisposition of taxa to occur more abundantly in one or more specific microhabitats, while temperature, salinity and tidal phase temporally structured both invertebrate and fish larval communities. The larvae of estuarine dependent marine fish occurred in mangrove microhabitats, suggesting they use structural mangrove patchiness as corridors or temporary nurseries before settling in situ, into their juvenile habitat. This study steers that the proposed nursery function or early stage role that mangroves play is driven by the structural uniqueness of mangrove microhabitats thus ensuring localised ecological linkages and functionality of these critical coastal environments.

Initial time dependence of wind- and density-driven Lagrangian residual velocity in a tide-dominated bay

The nonlinear effect of the summer southeast wind and density on the 3D structures of the full Lagrangian residual velocity (LRV) was quantified for a generally nonlinear system, using Jiaozhou Bay (JZB), China as the test site. In the tidally energetic JZB, the basic patterns of the wind- and density-driven full LRVs were found to be consistent with semi-analytical solutions but highly dependent on initial times. The wind-driven full LRVs at different tidal phases flowed similarly downwind over shoals and upwind in the deep region; however, the main branches could migrate across nearly half of the bay. A density-driven, clockwise flow was dominant in the western inner bay at low tide, but it almost disappeared at high tide. The effect of density generally enhanced the outward flow in the surface layer and inward flow in the bottom layer. Along-trajectory integrated momentum balances indicated that viscosity was the main factor responsible for the time dependence of the wind-driven full LRVs, while viscosity, barotropic and baroclinic pressure gradients were the main drivers of the intra-tidal variations in the density-driven full LRVs. Generally, the summer wind and density had opposing effects, although their influence was weaker than that of the tide and could not change the patterns of the tide-driven full LRVs. When analysing the effects of wind and density on the coastal circulation in JZB, both the 3D structures and the possibility of a high initial tidal phase dependency should be considered.

Simulation of the Hydrodynamic Field in Nhat Le Estuary, Quang Binh Province

Hydrodynamic field is the primary research problem of all studies on coastal estuarine areas. Over the years, there have been many studies on Nhat Le estuary's region (Quang Binh). Still, these studies have not focused on simulating the characteristics of the hydrodynamics of this area. This study will present the ability to apply a mathematical model to simulate hydrodynamic fields for the region of Nhat Le estuary and Quang Binh sea by constructing the MIKE 21 model set based on the actual measurement database by the Center for Environmental Fluid Dynamics implemented in 2018. Through the calculation scenarios under different conditions, the longshore current mainly consists of Southeast - Northwest (especially with NE waves, the current direction is Northwest - Southeast) with current speed mostly in the range of 0.1 - 0.4 m/s. In estuarine areas, river flows have complicated developments, including many component flows. In the dry season, the river flow is not strong and is dominated by changes in the tide phase, withdrawal in a day. There are days of high flood flow in the flood season, overwhelming the tidal currents; the maximum flow velocity at the door can reach more than 6 m/s. Waves in the southwest monsoon season are relatively small, about 0.25 - 0.6 m; while the waves in the Northeast monsoon season are quite large and very strong during the storm, but when the depth is about -3 to -4 m, the wave height decreases sharply, spreading to the door. In particular, when there are floods in the river, the waves that propagate through this depth will almost calm.

Proposal of new indexes for development characteristics of storm surge considering topographical features and tides

ABSTRACT We focused on the effects of tides on storm surge deviations. According to previous studies, storm surge deviations depend on when the typhoon strikes in the tidal phase because the water depth of a bay varies with tides. The previous studies concluded that the dependence can be explained by the conventional formula. However, the results of our numerical simulations could not be explained quantitatively by the conventional formula and require a development mechanism for storm surges that are not expressed in the formula, to explain the dependency. Therefore, we focused on the water depth gradient, and confirmed from the numerical simulation results that the depth gradient greatly influenced the development characteristics of storm surges. Moreover, a new formula considering the depth gradient was derived, and the tidal dependence of storm surge deviations was investigated. Based on the new formula, two indexes that indicate the effect of the water depth gradient and the effect of tides on storm surges were derived. We examined the indexes to clearly understand the development characteristics of storm surges. Finally, the validity of the derived indexes was investigated by comparing the computed surge heights based on the indexes with the results of the numerical simulations.

Tidal Influence on Seismic Activity During the 2011–2013 El Hierro Volcanic Unrest

AbstractThe El Hierro volcanic unrest started in July 2011, with an increase in observed seismicity rates and surface deformation. After the initial onset, hypocenters migrated southward through September 2011, culminating in a submarine eruption beginning on October 10, 2011 and finishing in February 2012. The seismic activity continued, with remarkable periods of unrest through 2012 and 2013. The most significant episodes of seismic activity during this unrest are related to magma migration at depth. In this work, we compute tidal stress for each earthquake, at its hypocenter depth, and assign them a tidal stress phase angle. We have found statistically significant correlations between the occurrence of earthquakes and tidal stress phase angles, corresponding mainly to increasing tidal stress change rates. We found primarily that the magnitude of vertical and E‐W horizontal tidal stress values and their changing rates with time were correlated with earthquake occurrence times. We also found that there is no correlation between tides and seismicity at times with no observed surface displacements, suggesting that tidal modulation might be related to overpressure during migration of magma. Tidal modulation changes with depth and the influence of ocean‐loading tides is stronger than the influence of solid Earth tides. Our results support the hypothesis that tidal stress may modulate the seismicity during volcanic unrest, particularly during shallow depth magma migration.

On the Problem of Modeling the Boat Wake Climate: The Florida Intracoastal Waterway

AbstractQuantifying and forecasting the impact of boat traffic on the health of coastal ecosystems must account for the multiscale nature of the process: from minutes (individual wakes), to days (tidal phase), weeks, and longer (tide modulation, seasonal traffic). Direct numerical simulations covering all these scales are difficult, not in the least because specifying the vessel type and navigation characteristics for every wake is practically impossible. To overcome this problem, we propose a statistical‐mechanics description of the wake field that focuses on classes of wakes, defined by a set of characteristic parameters, and their joint probability density in the characteristic‐parameter space. Here, we demonstrate the first steps of the approach using existing numerical tools and parametrizations. Because vessel type and navigation characteristics are not available, an investigation of wake parameter space is not possible at this time. Instead, we use the leading‐order Froude‐number parametrization defined by a linear model to classify the wake population observed during the field experiment. Numerical tests applying the FUNWAVE‐TVD model across all wake‐classes identified show excellent skills for weakly dispersive wakes. The model is challenged by the short waves generated by small, slow boats. However, simulations suggest that the problem is confined to the deeper water domain and linear evolution. Nonlinear wake shoaling, essential for modeling wake‐induced sediment transport and wake impact on the environment, is described well.

Assessing the Influence of Shoreline Adaptation on Tidal Hydrodynamics: The Role of Shoreline Typologies

AbstractIn coastal embayments, tidal dynamics are influenced by mean sea level and shoreline configuration. As sea levels rise and coastal communities modify their shorelines to mitigate future flooding, spatial patterns of inundation, tidal amplitude, and tidal phase will change in response. Here we apply a hydrodynamic model to systematically investigate the effect of local‐scale, spatially refined shoreline protection on regional tidal dynamics and peak water levels in San Francisco Bay, California. We find that individual shoreline protection scenarios produce relatively small changes in tidal amplitudes at 50 and 100 cm of sea‐level rise but can result in amplification of the M2 tide by up to 40% at 200 cm of sea‐level rise. Protection of shorelines with gradually sloping topography and space for floodwater accommodation generally has the largest influence on tidal response, both locally and regionally. In the northern part of San Francisco Bay, tides down‐estuary of protected shorelines move closer to a standing wave, while up‐estuary tides become more progressive. In the southern part of the bay, which is already close to a standing wave, effects are more localized and variable. Overall, the tidal response to shoreline protection is a function of both the geographic location within the embayment as well as the geomorphic characteristics of the local landscape that is protected. Understanding the relative influence of local shoreline modifications on tidal dynamics under a range of sea‐level rise scenarios is critical to developing effective shoreline adaptation alternatives that maximize flood mitigation.

Pollutant transport and residence time of a shallow and narrow coastal lagoon estimated using a numerical model

Setiu Wetland is rapidly developing into an aquaculture and agriculture hub, causing concern about its water quality condition. To address this issue, it is imperative to acquire knowledge of the spatial and temporal distributions of pollutants. Consequently, this study applied combinations of hydrodynamic and particle tracking models to identify the transport behaviour of pollutants and calculate the residence time in Setiu Lagoon. The particle tracking results indicated that the residence time in Setiu Lagoon was highly influenced by the release location, where particles released closer to the river mouth exhibited shorter residence times than those released further upstream. Despite this fact, the pulse of river discharges successfully reduced the residence time in the order of two to twelve times shorter. Under different tidal phases, the residence time during the neap tide was longer regardless of heavy rainfalls, implying the domination of tidal flow in the water renewal within the lagoon.

Estimation of tidal excursion length along the Shatt Al-Arab estuary, Southern Iraq

The tidal excursion length along the Shatt Al-Arab estuary was estimated based on the mathematical relation proposed by Parsa and Shahidi (2010). The field measurements of water level, bathymetry, and discharges were conducted to fulfill the objective of the study. The results revealed that the tidal excursion length is site-specific and depends on the characteristics of location which include tidal phases, bathymetry, and geometry. However, the results indicated that there are pronounced differences in tidal excursions lengths between the spring and neap tide phases in all studies stations. The spring tide coincided with the maximum tidal excursion lengths in Shatt Al-Arab estuary with 16.537, 16.187, 11.122, and 9.139 km in the estuary mouth, Faw, Siba, and Abo Flous stations respectively. While the neap tidal excursion lengths were 12.298, 9.254, and 7.269 km in Faw, Siba, and Abo Flous stations respectively.

An Optimized-Parameter Spectral Clustering Approach to Coherent Structure Detection in Geophysical Flows

In Lagrangian dynamics, the detection of coherent clusters can help understand the organization of transport by identifying regions with coherent trajectory patterns. Many clustering algorithms, however, rely on user-input parameters, requiring a priori knowledge about the flow and making the outcome subjective. Building on the conventional spectral clustering method of Hadjighasem et al. (2016), a new optimized-parameter spectral clustering approach is developed that automatically identifies optimal parameters within pre-defined ranges. A noise-based metric for quantifying the coherence of the resulting coherent clusters is also introduced. The optimized-parameter spectral clustering is applied to two benchmark analytical flows, the Bickley Jet and the asymmetric Duffing oscillator, and to a realistic, numerically generated oceanic coastal flow. In the latter case, the identified model-based clusters are tested using observed trajectories of real drifters. In all examples, our approach succeeded in performing the partition of the domain into coherent clusters with minimal inter-cluster similarity and maximum intra-cluster similarity. For the coastal flow, the resulting coherent clusters are qualitatively similar over the same phase of the tide on different days and even different years, whereas coherent clusters for the opposite tidal phase are qualitatively different.

Seasonal evolution of winds, atmospheric tides, and Reynolds stress components in the Southern Hemisphere mesosphere–lower thermosphere in 2019

Abstract. In this study we explore the seasonal variability of the mean winds and diurnal and semidiurnal tidal amplitude and phases, as well as the Reynolds stress components during 2019, utilizing meteor radars at six Southern Hemisphere locations ranging from midlatitudes to polar latitudes. These include Tierra del Fuego, King Edward Point on South Georgia island, King Sejong Station, Rothera, Davis, and McMurdo stations. The year 2019 was exceptional in the Southern Hemisphere, due to the occurrence of a rare minor stratospheric warming in September. Our results show a substantial longitudinal and latitudinal seasonal variability of mean winds and tides, pointing towards a wobbling and asymmetric polar vortex. Furthermore, the derived momentum fluxes and wind variances, utilizing a recently developed algorithm, reveal a characteristic seasonal pattern at each location included in this study. The longitudinal and latitudinal variability of vertical flux of zonal and meridional momentum is discussed in the context of polar vortex asymmetry, spatial and temporal variability, and the longitude and latitude dependence of the vertical propagation conditions of gravity waves. The horizontal momentum fluxes exhibit a rather consistent seasonal structure between the stations, while the wind variances indicate a clear seasonal behavior and altitude dependence, showing the largest values at higher altitudes during the hemispheric winter and two variance minima during the equinoxes. Also the hemispheric summer mesopause and the zonal wind reversal can be identified in the wind variances.

Qualidade da Água e Hidrodinâmica como Parâmetros Ambientais na Piscicultura de Tanques-Rede no Estuário do Rio Amazonas

O cultivo de peixes em tanques-rede é uma atividade sensível à poluição ambiental, mas também apresenta capacidade de causar poluição ao meio. Nosso objetivo foi investigar as variações espaço-sazonais de parâmetros físico-químicos e microbiológicos da qualidade da água (QA) em um trecho do Rio Matapi (AP), utilizado para piscicultura de tanque-rede. Três sítios amostrais distribuídos em ≈15 km de extensão do Rio Matapi foram estudados para monitorar variações espaço-temporais da QA, sendo o ponto central utilizado para medidas de descargas líquidas e parâmetros hidrodinâmicos. Observou-se significativa influência sazonal hidrodinâmica sobre QA (p<0,05), mas reduzida influência espacial desta última em relação aos sítios amostrais, inclusive o de cultivo em tanques-rede (p>0,05). Observou-se que o período hidrológico-sazonal, a fase da maré e a localização dos sítios, explicam a variação de QA nestes ambientes estuarinos (p<0,05, ANCOVA). Concluímos que o cultivo em tanques-rede apresentou baixo impacto ambiental, sendo localmente viável, contudo sensível às condições hidrodinâmicas e escalas geográficas estudadas.Palavras-chave: estuário, peixe, gradientes hidrológicos, impacto ambiental. Water quality and hydrodynamic as environmental parameters in net-tank fish farming in the Amazon River Estuary ABSTRACTThe cultivation of fish in net cages is an activity sensitive to environmental pollution, but also has the ability to cause environmental impact. The aim of study was to investigate spatial-temporal variations of physico-chemical and microbiological parameters of water quality (WQ) in a stretch of the Matapi River, State of Amapá/Brazil. This study presents an environmental analysis of fish culture on net cages systems, specially hydrodynamic and WQ condictions. Three sampling sites were distributed in ≈15 km of river to quantify variations of the WQ and hydrodynamic parameters. We notice a significant hydrodynamic seasonal influence of the WQ (p <0.05), which presented reduced spatial influence (p>0.05). We observed that both the hydrological-seasonal condictions, tide phase and site localization, explain the variation of WQ in these floodplans area (p<0.05, ANCOVA). We conclude that net cage system presented low environmental impact but local viability, both dependent on hydrodynamic conditions and scale studied.Keywords: estuary, fish, hydrological gradients, environmental impact.

Effect of Tidal Phase on Some Physical and Chemical Properties of Khor Al-Zubair, Southern Iraq

The hydrodynamic behavior of Khor Al-Zubair (south of Basrah) was studied for a whole year (2017-2018), which is the period of the current study, to find out the extent of its impact on some physical and chemical properties. The current study included measurements (pH, salinity, temperature, dissolved oxygen, turbidity, sulfate, nitrite, nitrate, phosphate) at two stations near Umm Qasr Port and Khor Al Zubair. The results revealed that the highest and lowest salinity values for both stations ranged between (43.2-43.82) ppt, (39.9-42.96) ppt, respectively.

A MODIFIED LINEAR SUPERPOSITION METHOD FOR THE INTERACTION OF TIDE AND STORM SURGE

Many previous methods of including tidal contributions in statistical estimates of coastal storm surges have used models that couple storm surges with tides at a small number of randomly sampled phases. Applying a small number of samples can introduce substantial aleatory uncertainty into the total water levels in areas where tide ranges are of comparable magnitude to the storm surges, such as much of the East Coast of the United States. The standard deviation of the uncertainty is related to the standard deviation of the tides (sigma_tides) by inverse of the square root of the number of tide samples. The authors applied a data set (provided to FEMA) consisting of 30 historical extra-tropical storms, each run at 4 tide phases (chosen such that two approximately coincided with high tide and two with low tide). The analysis examined tide-only, surge-only and tide coupled to surge model results at 34 stations located by the authors to cover the spatial extent of the study area and to include both open coast and sheltered inland waterways.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/__kfqH2i78E

Migrating tide climatologies measured by a high-latitude array of SuperDARN HF radars

Abstract. This study uses hourly meteor wind measurements from a longitudinal array of 10 high-latitude SuperDARN high-frequency (HF) radars to isolate the migrating diurnal, semidiurnal, and terdiurnal tides at mesosphere–lower-thermosphere (MLT) altitudes. The planetary-scale array of radars covers 180∘ of longitude, with 8 out of 10 radars being in near-continuous operation since the year 2000. Time series spanning 16 years of tidal amplitudes and phases in both zonal and meridional wind are presented, along with their respective annual climatologies. The method to isolate the migrating tides from SuperDARN meteor winds is validated using 2 years of winds from a high-altitude meteorological analysis system. The validation steps demonstrate that, given the geographical spread of the radar stations, the derived tidal modes are most closely representative of the migrating tides at 60∘ N. Some of the main characteristics of the observed migrating tides are that the semidiurnal tide shows sharp phase jumps around the equinoxes and peak amplitudes during early fall and that the terdiurnal tide shows a pronounced secondary amplitude peak around day of year (DOY) 265. In addition, the diurnal tide is found to show a bi-modal circular polarization phase relation between summer and winter.

Mapping bull kelp canopy in northern California using Landsat to enable long-term monitoring

Extending from central California to Alaska, bull kelp (Nereocystis luetkeana) forms seasonal kelp forests that are iconic coastal ecosystems in much of the eastern Pacific. Historical and ongoing field surveys and aerial imagery are used to provide biological data on kelp canopy cover and health, but satellite remote sensing provides the opportunity to generate consistent, long-term datasets over a large spatial scale. Robust satellite-based timeseries measurements of giant kelp (Macrocystis pyrifera) are available for much of the California coastline (e.g., Santa Barbara to Santa Cruz), but there have been no equivalent publications for bull kelp. Recent loss of bull kelp in northern California emphasized the need for more expansive long-term monitoring of canopy trends. We tested various kelp classification approaches using Multiple Endmember Spectral Mixture Analysis (MESMA) applied to Landsat imagery, which allowed sufficient temporal and spatial data collection during bull kelp's narrow seasonal maximum, and compare with the California Department of Fish and Wildlife (CDFW) aerial survey canopy area product. We addressed five main topics that have relevance to enabling Landsat in long-term monitoring of bull kelp canopy coverage in northern California: (1) the effect of MESMA configurations applied to Landsat imagery, including software dependencies and endmember configurations, (2) comparison of Landsat to traditional surveys, (3) differences across Landsat sensors, (4) tidal influence on canopy area, and (5) trends in the decadal timeseries. We found that there was no statistical difference (p = 0.53) between MESMA platforms (IDL-based and a Python-scripted method; RMSE 1.5 km2 or 17.6% when normalized by the range in CDFW), and that a 7-endmember MESMA model provided the lowest RMSE (1.4 km2 or 16.9%). Furthermore, while tidal phases can submerge or emerge kelp canopy and thus potentially affect kelp detection, we found a weak and statistically insignificant correlation between tides and performance of our remote estimate of kelp canopy area. Canopy estimations from Landsat-8 images yielded a higher NRMSE than Landsat-4 and -5 images, but the lack of matchup limits comparison. Imagery from early fall yielded the largest coverage estimates. Overall, our results show that Landsat enables broad remote measurement of bull kelp canopy coverage to supplement existing survey methods and increase continuity of timeseries for monitoring long-term trends.