Search results | Digital Commons of Moss Landing Marine Laboratories

Title: Corrigendum to "A closer look at regime shifts based on coastal observations along the eastern boundary of the North Pacific",
Description: , , ,
Author: Breaker
Date: 2008-01-01T00:00:00Z

Title: Tidal and nontidal oscillations in Elkhorn Slough, CA,
Description: Elkhorn Slough is a shallow, tidally forced estuary that is directly connected to Monterey Bay. It is ebb-dominated and, due to continued erosion, the tidal prism has tripled over the past 40 years. Water level measurements at four locations are used to examine tidal and nontidal oscillations in Elkhorn Slough. The tidal response of Elkhorn Slough differs from that of Monterey Bay primarily due to the generation of a relatively large number of shallow-water tidal constituents that are due to tidal distortion caused by friction along the bottom and lateral boundaries, intertidal storage, and nonlinear advection. The shallow-water constituents range from 3 to almost 15 cycles per day (cpd) and include a rich variety of overtides and compound tides, whose amplitudes generally increase toward the head of the slough. The tidal harmonics are seasonally dependent, with lower amplitudes during the fall and winter and higher amplitudes in summer. The tidal constituents were examined using two types of spectral decomposition, the conventional power spectrum and the more recent Hilbert spectrum. Unlike the power spectrum, the Hilbert spectrum does not reveal any harmonic structure in the data. Energy associated with tidal distortion in this case appears to be broadly distributed across the spectral continuum. At least four nontidal oscillations occur in Elkhorn Slough with frequencies of 26.0, 39.7, 52.7, and 66.9 cpd. The Hilbert spectrum reveals maxima at 26, 39.7, and 66.9 cpd, but not at 52.7 cpd, suggesting that it is harmonically related to the oscillation at 26.0 cpd. The nontidal oscillations fall into the range of frequencies associated with the natural oscillations of Monterey Bay. However, evolutionary power spectra indicate that they appear to be permanent features of the system and thus are not necessarily consistent with seiche-like oscillations that are often transient and subject to damping. These oscillations could be caused by several factors including edge waves along the coast of Monterey Bay, long-period surface waves of atmospheric origin that enter the bay from offshore, or breaking internal waves in and around the Monterey Submarine Canyon. In conclusion, detailed hydrodynamic models are needed to provide a better understanding of how tidal harmonics are generated and preserved in Elkhorn Slough, and to determine the origin of the natural oscillations in Monterey Bay. © 2007 Coastal and Estuarine Research Federation., Cited By (since 1996):12, ,
Author: Breaker, Broenkow, Watson, Jo
Date: 2008-01-01T00:00:00Z

Title: Expressions of 1976-1977 and 1988-1989 regime shifts in sea-surface temperature off Southern California and Hawai'i,
Description: Sea-surface temperatures off southern California from Scripps Pier and from Koko Head, Hawai'i, were examined to determine what impact regime shifts that occurred in 1976-1977 and 1988-1989 had on environmental conditions at each location. Cumulative sums were employed to enhance the detection process. The cumulative sum time histories revealed major turning points at both locations at the time of the 1976-1977 event. At both locations, increases in temperature were indicated, consistent with the phase change in the Pacific Decadal Oscillation that took place at that time. The cumulative sums also indicated major turning points at both locations during the 1988-1989 event. A new procedure called the method of expanding means was employed to determine the long-term impact of these events. By comparing means before and after a given event it is possible to observe the magnitude of the change and to what extent it is sustained. For the 1976-1977 regime shift, temperatures increased rapidly and remained consistently higher, by ∼1°C for 2-3 yr at Scripps Pier. This increase occurred over a period of approximately 7 months and accounts for more than half of the total warming that has occurred at that location since 1920. At Koko Head, a similar response was observed with a sustained increase of approximately +0.5°C. The oceanic response to the 1988-1989 event was quite different. At Scripps Pier, temperatures before and after this event did not show any tendency to converge to significantly different values out to periods of 2-3 yr. At Koko Head, mean temperatures did converge to slightly different values after 1 yr, with mean values being consistently lower after this event (∼-0.4°C). It was shown that in some cases changes associated with these events could be identified in the original data, but without the help of cumulative sums, it is usually not possible to make a clear distinction between changes of interest and other sources of variability. Finally, decorrelation time scales for the records at both locations were estimated and found to be on the order of a year, implying spatial scales that are at least synoptic (tens to hundreds of kilometers)., Cited By (since 1996):1, ,
Author: Breaker, Flora
Date: 2009-01-01T00:00:00Z

Title: A curious relationship between the winds and currents at the western entrance of the Santa Barbara Channel,
Description: , , , Relationships between the surface winds and Acoustic Doppler Current Profiler (ADCP) currents at 20 levels (25 to 329 m) at the western entrance of the Santa Barbara Channel (SBC) at National Data Buoy Center (NDBC) buoy 46054 are evaluated for the 1 year period from 1 June 1996 through 31 May 1997 using a relatively new technique for correlating vectors. Gaps in the data were filled and the resulting time series examined to insure that the statistical properties of the edited data had not been significantly altered. Vertical current profiles, averaged over the year, indicate that the mean signal, although well-defined, is smaller than the variability about the mean. Vertical profiles of current speed and direction suggest the possibility of at least a twolayer system of circulation in the SBC with flow between 25 and 180 m being to the SSW and flow from 260 to 329 m being to the ENE, in agreement with previous results. Because of the existing dynamical balances, the currents are oriented approximately SW/NE, and the direction of the vertical current shear (i.e., the thermal wind) is essentially constant with depth. Thus warmer waters lie to the north and west, and colder waters, essentially south of the buoy, are consistent with observed cyclonic circulation at the western entrance of the channel. Vector correlations over the entire year indicate that the winds and currents are poorly correlated,, ,
Author: Breaker, Gemmill, de Witt, Crosby
Date: 2003-01-01T00:00:00Z

Title: Erratum,
Description: Oceanography, CODEN: CSHRD, , ,
Author: Breaker
Date: 2005-01-01T00:00:00Z

Title: Sea level variations in the regional seas around Taiwan,
Description: The patterns and trends of sea level rise in the regional seas around Taiwan have been investigated through the analyses of long-term tide-gauge and satellite altimetry data. Series of tide-gauge data extending over 50 years reveal decadal and interannual variations and spatially-inhomogeneous patterns of generally rising sea level. The East Asia tide-gauge stations around Taiwan show an average trend of +2.4 mm/yr from 1961-2003, which is larger than the reported global rate of +1.8 mm/yr for the same period. These stations also show significantly larger sea level rise rates (+5.7 mm/yr) than global values (+3.1 mm/yr) during the period from 1993-2003. Consistent with the coastal tide-gauge records, satellite altimetry data show similar increasing rates (+5.3 mm/yr) around Taiwan during the same period. Comparisons with temperature anomalies in the upper ocean suggest that thermal expansion and heat advection in the upper layer contribute significantly to the long-term sea level variations in this area with correlations >0.9 for observations after 1992. Thermosteric sea level variations may also explain the interannual and decadal variations of the observed sea level rises around Taiwan. Our analysis also indicates that the altimetry data are only part of a long-term, larger-scale signal. Finally, we have found that a non-linear smoother, LOESS, is more suitable for extracting long-term trends in sea level than the traditional linear regression approach. © Springer Science+Business Media B.V. 2010., Cited By (since 1996):3, ,
Author: Tseng, Breaker, Chang
Date: 2010-01-01T00:00:00Z

Title: Predicting offshore temperatures in Monterey Bay based on coastal observations using linear forecast models,
Description: The linear systems approach is used to forecast offshore near-surface and subsurface temperatures in Monterey Bay and further offshore based on coastal sea surface temperatures (SSTs) at Pacific Grove. SST from Pacific Grove provided the input to the system and the forecast parameters or outputs were temperature at 1 m and 100 m at the M1 buoy located 20 km from Pacific Grove near the center of Monterey Bay, and temperature at 1 m at the M2 buoy located 55 km from Pacific Grove. To forecast temperatures at the M1 and M2 buoys, Box-Jenkins, State-Space, ARX, and ARMAX models were employed. Model formulation, implementation, forecasting procedures, and methods of evaluation are presented. Seven and 30-day forecasts were routinely made for the daily observations although other forecast horizons were employed. For all models and variables, RMS differences between the forecasts and the observations increased rapidly between 1 and 15 days. Beyond about 30 days, RMS differences tended to remain almost constant with increasing forecast horizon. Overall, model forecasts were best for temperature at 100 m at the M1 buoy, due to the fact that temperature is well conserved at depth. Differences in performance between the models were small but the ARMAX model often produced forecasts that were slightly better than the rest, a result that we attribute to a more complete specification of the noise. Although the Box-Jenkins and State-Space models have the potential to produce better forecasts, because more terms must be specified to implement them, the opportunity to produce less-than-optimal results is also greater. Finally, because of seasonal changes in the circulation of Monterey Bay, it is possible that causality was violated, upon occasion, placing certain constraints on the results. Models based on the linear systems approach, where they can be implemented, could serve as a useful adjunct to hydrodynamic ocean circulation models by providing additional information for model initialization, evaluation, and data assimilation. Using the same approach, operational forecasts of the coastal circulation could be made by including forecast winds and the predicted tides as inputs, and CODAR-observed surface currents as the output. In a less glamorous but still useful role, they could be used to fill significant gaps in offshore records where data continuity and quality are important. © 2008 Elsevier Ltd. All rights reserved., Cited By (since 1996):2, ,
Author: Breaker, Brewster
Date: 2009-01-01T00:00:00Z

Title: Nonlinear aspects of sea surface temperature in Monterey Bay,
Description: Nonlinear aspects of sea surface temperature (SST) in Monterey Bay are examined, based on an 85-year record of daily observations from Pacific Grove, California. Oceanic processes that affect the waters of Monterey Bay are described, processes that could contribute to nonlinearity in the record. Exploratory data analysis reveals that the record at Pacific Grove is non-Gaussian and, most likely, nonstationary. A more recent test for stationarity based on a power law approximation to the slope of the power spectrum indicates that the record is stationary for frequencies up to ∼8 cycles per year (∼45 days), but nonstationary at higher frequencies. To examine the record at Pacific Grove for nonlinear behavior, third-order statistics, including the skewness, statistical measures of asymmetry, the bicorrelation, and the bispectrum, were employed. The bicorrelation revealed maxima located approximately 365 days apart, reflecting a nonlinear contribution to the annual cycle. Based on a 365-day moving window, the running skewness is positive almost 80% of the time, reflecting the overall impact of warming influences. The asymmetry is positive approximately 75% of the time, consistent with the asymmetric shape of the mean annual cycle. Based on the skewness and asymmetry, nonlinearities in the record, when they occur, appear to be event-driven with time scales possibly as short as several days, to several years. In many cases, these events are related to warm water intrusions into the bay, and El Niño warming episodes. The power spectrum indicates that the annual cycle is a dominant source of variability in the record and that there is a relatively strong semiannual component as well. To determine whether or not the annual and semiannual cycles are harmonically related, the bispectrum and bicoherence were calculated. The bispectrum is nonzero, providing a strong indication of nonlinearity in the record. The bicoherence indicates that the annual cycle is a major source of nonlinearity and further implies that the annual and semiannual cycles are harmonically related. Based on the wavelet power spectrum (WPS), the appearance of the semiannual cycle is transitory; however, pathways between the annual and semiannual cycles appear at certain times when nonlinear interaction between them could occur. Comparisons between the WPS and the running skewness suggest that there is a tendency for periods when pathways exist, to coincide with increased positive skewness, and, often, with El Niño warming episodes. The Hilbert-Huang transform, a relatively new tool for nonstationary and nonlinear spectral analysis, was used to further examine the origin of the semiannual cycle. The time-dependent Hilbert spectrum reveals large and erratic variations in frequency associated with semiannual cycle but far greater stability associated with the annual cycle. As a result, the time-integrated Hilbert spectrum does not indicate the presence of a semiannual cycle. The method of surrogates from the field of nonlinear dynamics was also employed to test the Hopkins record for nonlinearity. Differences between the data and the surrogates were found that were statistically significant, implying the existence of nonlinearity in the record. Using the method of surrogates together with a one-year moving window, El Niño warming episodes appear to be a likely source of nonlinearity, consistent with the other analyses that were performed. Finally, the influence of stochastic variability due to serial correlation in the data was examined by comparing standardized statistics for the observations and for simulations based on an autoregressive model whose properties were obtained from the observations. The magnitude of the variability for the simulations was found to be far less than that associated with the original data, and thus stochastic variability does not appear to be a factor that significantly affects the interpretation of our results. © 2006 Elsevier Ltd. All rights reserved., Cited By (since 1996):5, CODEN: POCNA, ,
Author: Breaker
Date: 2006-01-01T00:00:00Z

Title: Sea surface temperature fronts in the California Current System from geostationary satellite observations,
Description: Sea surface temperature (SST) fronts are determined for the 2001-2004 time period from Geostationary Operational Environmental Satellites (GOES) data in the California Current System (CCS). The probability of detecting a SST front at an individual pixel location in the CCS is presented as a bi-monthly climatology. Fronts clearly indicate the seasonal evolution of coastal upwelling, as well as meanders and filaments that are often linked with irregularities in coastline geometry. Winter is characterized by low frontal activity along the entire coast. Fronts first appear close to the coast during spring, particularly south of Cape Blanco, where upwelling favorable winds are already persistent. The area of high frontal activity continues to increase during summer, especially between Monterey Bay and Cape Blanco, extending more than 300 km from the coast. The region with high frontal activity widens at ∼2.6 km day-1. Off northern Baja California, a band with persistent fronts is found close to the coast year-round, but there is no evidence of a seasonal widening of the area of higher activity. During fall, the weakening of upwelling favorable winds leads to a gradual decrease in frontal activity. An empirical orthogonal function (EOF) decomposition reveals the development of SST fronts associated with seasonal upwelling for locations north of Monterey Bay, with less summer intensification to the south. The first appearance of fronts close to the coast during spring and the occurrence of the fronts offshore later in the season are represented by additional statistically significant EOF modes. Copyright 2006 by the American Geophysical Union., , , ,
Author: Castelao, Mavor, Barth, Breaker
Date: 2006-01-01T00:00:00Z

Title: Energy production trend extraction using ensemble empirical mode decomposition
Description: The purpose of this study is to illustrate, by example, a method called Ensemble Empirical Mode Decomposition (EEMD). Specifically, the method was used to extract the long-term trend from a time series of energy production data from the United Kingdom for the period from January 1978 through July 2011. This record is dominated by two components: an annual cycle and a long-term trend. Using EEMD, it was not difficult to extract the long-term trend. However, three components or modes from the EEMD were required to capture the underlying pattern that was the basis for the trend. This trend was also evaluated in terms of a definition for the trend given in [6]. It was found that our trend did not conform to the definition given in [6], leading to the conclusion that it is indeed a difficult problem, or perhaps impossible, to arrive at a precise definition of the trend that will be universally applicable.
Author: Breaker
Date: 2013-01-01T00:00:00Z

Title: Nonhydrostatic simulations of the regional circulation in the Monterey Bay area,
Description: The regional circulation in the vicinity of Monterey Bay is complex and highly variable. We use a one-way coupled, nonhydrostatic version of the Dietrich Center for Air Sea Technology (DieCAST) ocean model to simulate the regional circulation. Seasonally varying local wind stress, topographic irregularities, coastal upwelling, and forcing from the open ocean are all important in this region. Satellite imagery often shows a cyclonic eddy inside the bay and an anticyclonic eddy outside the bay. The offshore anticyclonic eddy is also associated with a year-round anticyclonic eddy over the Monterey Submarine Canyon (MSC). The offshore eddy is better organized during winter. It is found that the California Undercurrent (200-400 m) does not enter the bay itself but is diverted offshore past the entrance of the bay, presumably to reform farther north along the coast. The main branch flows northward contributing to the deep anticyclonic eddy located approximately 50 km offshore of Monterey Bay. The simulations show that vertical motion is greater during summer than winter, as expected. During spring upwelling, the deep waters often upwell along the walls of the canyon and then spread and mix with surrounding waters. The deep circulation enhances mixing significantly due to the topography. We further investigate the regional circulation by comparing it with the cases where the deep canyon was filled gradually. Vortex stretching over the canyon just beyond the entrance to Monterey Bay and along the adjacent continental slopes contributes to cyclonic circulation at deeper levels. Vertical sections of velocity along the axis of MSC indicate horizontal and vertical patterns of flow that are generally consistent with past observations on the circulation of Monterey Bay. Copyright 2007 by the American Geophysical Union., , , ,
Author: Tseng, Breaker
Date: 2007-01-01T00:00:00Z

Title: Mapping and monitoring large-scale ocean fronts off the California coast using imagery from the GOES-10 geostationary satellite,
Description: , , ,
Author: Breaker, Mavor, Broenkow
Date: 2005-01-01T00:00:00Z

Title: Establishing an objective basis for image compositing in satellite oceanography,
Description: This study strives to establish an objective basis for image compositing in satellite oceanography. Image compositing is a powerful technique for cloud filtering that often emphasizes cloud clearing at the expense of obtaining synoptic coverage. Although incomplete cloud removal in image compositing is readily apparent, the loss of synopticity, often, is not. Consequently, the primary goal of image compositing should be to obtain the greatest amount of cloud-free coverage or clarity in a period short enough that synopticity, to a significant degree, is preserved. To illustrate the process of image compositing and the problems associated with it, we selected a region off the coast of California and constructed two 16-day image composites, one, during the spring, and the second, during the summer of 2006, using Advanced Very High Resolution Radiometer (AVHRR) InfraRed (IR) satellite imagery. Based on the results of cloud clearing for these two 16-day sequences, rapid cloud clearing occurred up to day 4 or 5, followed by much slower cloud clearing out to day 16, suggesting an explicit basis for the growth in cloud clearing. By day 16, the cloud clearing had, in most cases, exceeded 95%. Based on these results, a shorter compositing period could have been employed without a significant loss in clarity. A method for establishing an objective basis for selecting the period for image compositing is illustrated using observed data. The loss in synopticity, which, in principle, could be estimated from pattern correlations between the images in the composite, was estimated from a separate time series of SST since the loss of synopticity, in our approach, is only a function of time. The autocorrelation function of the detrended residuals provided the decorrelation time scale and the basis for the decay process, which, together, define the loss of synopticity. The results show that (1) the loss of synopticity and the gain in clarity are inversely related, (2) an objective basis for selecting a compositing period corresponds to the day number where the decay and growth curves for synopticity and clarity intersect, and (3), in this case, the point of intersection occurred 3.2 days into the compositing period. By applying simple mathematics it was shown that the intersection time for the loss in synopticity and the growth in clarity is directly proportional to the initial conditions required to specify the clarity at the beginning of the compositing period, and inversely proportional to the sum of the rates of growth for clarity and the loss in synopticity. Finally, we consider these results to be preliminary in nature, and, as a result, hope that future work will bring forth significant improvements in the approach outlined in this study. © 2009 Elsevier Inc. All rights reserved., Cited By (since 1996):3, Oceanography, CODEN: RSEEA, ,
Author: Breaker, Armstrong, Endris
Date: 2010-01-01T00:00:00Z

Title: The response of Monterey Bay to the 2010 Chilean earthquake,
Description: The primary frequencies contained in the arrival sequence produced by the tsunami from the Chilean earthquake of 2010 in Monterey Bay were extracted to determine the seiche modes that were produced. Singular Spectrum Analysis (SSA) and Ensemble Empirical Mode Decomposition (EEMD) were employed to extract the primary frequencies of interest. The wave train from the Chilean tsunami lasted for at least four days due to multipath arrivals that may not have included reflections from outside the bay but most likely did include secondary undulations, and energy trapping in the form of edge waves, inside the bay. The SSA decomposition resolved oscillations with periods of 52-57, 34-35, 26-27, and 21-22 minutes, all frequencies that have been predicted and/or observed in previous studies. The EEMD decomposition detected oscillations with periods of 50-55 and 21-22 minutes. Periods in the range of 50-57 minutes varied due to measurement uncertainties but almost certainly correspond to the first longitudinal mode of oscillation for Monterey Bay, periods of 34-35 minutes correspond to the first transverse mode of oscillation that assumes a nodal line across the entrance of the bay, a period of 26- 27 minutes, although previously observed, may not represent a fundamental oscillation, and a period of 21-22 minutes has been predicted and observed previously. A period of ~37 minutes, close to the period of 34-35 minutes, was generated by the Great Alaskan Earthquake of 1964 in Monterey Bay and most likely represents the same mode of oscillation. The tsunamis associated with the Great Alaskan Earthquake and the Chilean Earthquake both entered Monterey Bay but initially arrived outside the bay from opposite directions. Unlike the Great Alaskan Earthquake, however, which excited only one resonant mode inside the bay, the Chilean Earthquake excited several modes suggesting that the asymmetric shape of the entrance to Monterey Bay was an important factor and that the directions of the incoming tsunami-generated waves were most likely different. The results from SSA and EEMD produced results that differed. Although a period of 34-35 minutes was observed in the SSA, it was not detected in the EEMD. In previous comparisons, however, we have observed that oscillations detected in EEMD were not detected in SSA. SSA also revealed an oscillation with a period of 26-27 minutes, not observed in the EEMD. This oscillation, however, may not represent a fundamental mode but instead a harmonic related to the first longitudinal mode of oscillation whose period is ~55 minutes. We conclude that both methods were useful in helping to interpret the results of this study., Cited By (since 1996):2, Oceanography, ,
Author: Breaker, Murty, Flora, Hunter
Date: 2011-01-01T00:00:00Z

Title: Use of acoustic tags to estimate natural mortality, spillover, and movements of lingcod (Ophiodon elongatus) in a marine reserve,
Description: Advances in electronic telemetry systems have led to fish tagging studies that are sufficiently long to provide estimates of natural mortality of many marine fishes. We used acoustic transmitters and an array of recording receivers to estimate natural mortality, residence times, and rates of movements of lingcod (Ophiodon elongatus) in a marine reserve in southeast Alaska. We surgically implanted acoustic tags in a total of 83 lingcod in December 1999 and July 2000, and distributed recording monitors with receiving ranges of at least 800 m throughout the reserve. The receivers were anchored on the seafloor in locations that resulted in overlapping receiving ranges, and thus created an array of receivers that completely encompassed an 8 km 2 reserve. In this way, we were able to estimate natural mortality rates and track movements of tagged lingcod into and out of the reserve from December 1999 through October 2001. Acoustic tag results indicated that most of the tagged fish frequently left the reserve, but were only absent for short time periods. Tagged fish showed a high degree of site fidelity. The large number of signals received from tagged fish enabled us to generate models that provided a way to predict the effects of marine reserves on yield and eggs per recruit for a cohort of female lingcod., Cited By (since 1996):8, Fish and Fisheries, ,
Author: Starr, O'Connell, Ralston, Breaker
Date: 2005-01-01T00:00:00Z

Title: On the natural oscillations of Monterey Bay: Observations, modeling, and origins,
Description: Observations of the natural oscillations of Monterey Bay have revealed periods that range from several minutes to almost one hour. These oscillations can be excited by winter storm events, and historical data show that they were also excited by tsunamis produced by the 1989 Loma Prieta Earthquake and the 1964 Great Alaskan Earthquake. However, these oscillations also tend to be continuous in nature although low in amplitude. The four lowest frequency oscillations have periods of approximately 55, 36, 27, and 22. min. The 55-min period corresponds to the first longitudinal mode of oscillation, and the 36-min period, to the first transverse mode. Numerical simulations are employed to examine the oscillating characteristics of the bay and to help ascertain their origin. The model results are consistent with earlier studies, suggesting that Monterey Submarine Canyon divides the bay into two separate oscillating basins, although water level and pressure data indicate that at least for the four lowest frequencies, these oscillations tend to be bay-wide. Spatial patterns extracted from model-generated power spectra at the four lowest frequencies show good agreement with the modal patterns predicted by Wilson et al. (1965).Impulsively generated seiche oscillations should be subject to relatively strong damping and consequently decay within several cycles. Thus, it is not clear why the oscillations tend to be continuous, since the natural oscillations that are observed in most basins are transient, due to the transient nature of the forcing. Model simulations further indicate that both wind and tidal forcing contribute to the oscillations. Several mechanisms that could be responsible for the natural oscillations of Monterey Bay on a continuous basis were considered but it is not clear which, if any, of these mechanisms is ultimately responsible for exciting them. However, if the source of their excitation is wide-ranging or global, then they are likely to occur elsewhere around the world as well. © 2010 Elsevier Ltd., Cited By (since 1996):5, CODEN: POCNA, ,
Author: Breaker, Tseng, Wang
Date: 2010-01-01T00:00:00Z

Title: Comparing sea level response at Monterey, California from the 1989 Loma prieta earthquake and the 1964 great Alaskan earthquake,
Description: Two of the largest earthquakes to affect water levels in Monterey Bay in recent years were the Loma Prieta Earthquake (LPE) of 1989 with a moment magnitude of 6.9, and the Great Alaskan Earthquake (GAE) of 1964 with a moment magnitude of 9.2. In this study, we compare the sea level response of these events with a primary focus on their frequency content and how the bay affected it, itself. Singular Spectrum Analysis (SSA) was employed to extract the primary frequencies associated with each event. It is not clear how or exactly where the tsunami associated with the LPE was generated, but it occurred inside the bay and most likely began to take on the characteristics of a seiche by the time it reached the tide gauge in Monterey Harbor. Results of the SSA decomposition revealed two primary periods of oscillation, 9-10 minutes, and 31-32 minutes. The first oscillation is in agreement with the range of periods for the expected natural oscillations of Monterey Harbor, and the second oscillation is consistent with a bay-wide oscillation or seiche mode. SSA decomposition of the GAE revealed several sequences of oscillations all with a period of approximately 37 minutes, which corresponds to the predicted, and previously observed, transverse mode of oscillation for Monterey Bay. In this case, it appears that this tsunami produced quarter-wave resonance within the bay consistent with its seiche-like response. Overall, the sea level responses to the LPE and GAE differed greatly, not only because of the large difference in their magnitudes but also because the driving force in one case occurred inside the bay (LPE), and in the second, outside the bay (GAE). As a result, different modes of oscillation were excited., Cited By (since 1996):4, ,
Author: Breaker, Murty, Norton, Carroll
Date: 2009-01-01T00:00:00Z

Title: Intraseasonal oscillations in sea surface temperature, wind stress, and sea level off the central California coast,
Description: , , , The wavelet transform is used to conduct spectral and cross-spectral analysis of daily time series of sea surface temperature (SST), surface wind stress, and sea level off the central California coast for an 18-year period from 1974 through 1991. The spectral band of primary interest is given by intraseasonal time scales ranging from 30 to 70 days. Using the wavelet transform, we examine the evolutionary behavior of the frequently observed 40–50 day oscillation originally discovered in the tropics by Madden and Julian, and explore the relative importance of atmospheric vs oceanic forcing for a range of periods where both could be important. Wavelet power spectra of each variable reveal the event-like, nonstationary nature of the intraseasonal band. Peaks in wavelet power typically last for 3–4 months and occur, on average, approximately once every 18 months. Thus, their occurrence and/or duration off central California is somewhat reduced in comparison to their presence in the tropics. Although peaks in wind stress often coincide with peaks in SST and/or sea level, no consistent relationships between the variables was initially apparent. The spectra suggest, however, that relationships between the variables, if and where they do exist, are event-dependent and thus have time scales of the same order. Cross-wavelet spectra between wind stress and SST indicate that periods of high coherence (>0.90) occur on at least six occasions over the 18-year period of record. Phase differences tend to be positive, consistent with wind forcing. For wind stress vs sea level, the cross-wavelet spectra indicate that periods of high coherence, which tend to correlate with lags close to zero, also occur, but are less frequent. As with SST, the periods of high coherence usually coincide with events in the wavelet power spectra. The somewhat weaker relationship between wind stress and sea level may be due to an independent contribution to sea level through remote forcing by the ocean originating in the tropics. Finally, simple dynamical arguments regarding the lag relationships between the variables appear to be consistent with the cross-wavelet results., ,
Author: Breaker, Liu, Torrence
Date: 2001-01-01T00:00:00Z

Title: The response of Monterey bay to the great Tohoku earthquake of 2011
Description: Cited By (since 1996):1, Export Date: 28 April 2014
Author: Breaker, Murty, Carroll, Teague
Date: 2011-01-01T00:00:00Z

Title: Estimating rates of acceleration based on the 157-year record of sea level from San Francisco, California, U.S.A.
Description: Breaker, L.C. and Ruzmaikin, A., 2013. Estimating rates of acceleration based on the 157-year record of sea level from San Francisco, California, U.S.A. The question of the acceleration of global sea level rise has gained increasing attention because the present rate of sea level rise is relatively small in comparison to the rates that are predicted to occur in the near future. Recent measurements have come under scrutiny on how to correctly analyze and interpret regional estimates of acceleration. In this context, we employ the Ensemble Empirical Mode Decomposition (EEMD), a data-adaptive method developed for the analysis of nonstationary and nonlinear data to estimate acceleration over the 157-year record of sea level from San Francisco, California. We define sea level acceleration (SLA) as the mean of the second differences of the residual from an EEMD. Using the residual provides a means by which to reduce or eliminate the contaminating influence of decadal and longer-period oscillations in sea level that are folded into estimates obtained using the conventional approach. For the entire record, a value of +0.011 ± 0.003 mm/y2 was obtained for the acceleration and its uncertainty, compared with +0.013 mm/y2, using the conventional approach. The effect of record length is examined by estimating the accelerations for truncated versions of the record, one starting in 1900 and a second in 1925. The accelerations differed in each case from the conventional values, as expected, because the methods are based on different definitions of SLA. © Coastal Education & Research Foundation 2013., Cited By (since 1996):1, Oceanography, CODEN: JCRSE
Author: Breaker, Ruzmaikin
Date: 2013-01-01T00:00:00Z

Title: Trends in sea surface temperature off the coast of Ecuador and the major processes that contribute to them
Description: Article, Monthly-averaged sea surface temperatures (SSTs) from seven adjoining sub-regions spanning the coast of Ecuador have been examined for long-term trends and the major processes that contribute to them. The study area extends from the coast out to 84°W longitude, and from 4°S to 2°N latitude. The period of observation extends from 1900 through 2014, a period of 115 years. Linear trend analysis shows that the slopes are positive in all sub-regions and statistically significant in 5 out of 7 of them. Based on the trends SSTs increased from + 0.10 °C to + 1.42 °C over the entire period with the greatest increases occurring in the sub-regions next to the coast and to a lesser extent in the northern and southern sub-regions. A second non-linear trend analysis was conducted using Ensemble Empirical Mode Decomposition (EEMD). The results from EEMD for the various sub-regions indicate that SSTs increased significantly from 1900 to at least 1940 in the majority of cases. After 1950, SSTs tended to fluctuate with a minimum that often occurred during the 1960s or 1970s. Since circa 1990, SSTs have experienced little change. Because the data tended to be spatially homogeneous, with two sub-regions being possible exceptions, a mean data set was calculated and likewise subjected to EEMD. The results show that SSTs have increased by approximately 1 °C since 1900 but the process has not been uniform. The increase in temperature between 1900 and at least 1940 approaches 1 °C, similar to the trends found in the majority of sub-regions. Between ~ 1950 and 1990, temperatures decreased slightly until the mid-1960s and then gradually increased until about 1990. Since ~ 1990 there has been no significant change in SST. Overall, the results of the global mean analysis are generally consistent with the sub-regional results. Several sources of variability have been tentatively identified that may contribute to the long-term changes in temperature that we have observed. Both spectral analysis and EEMD suggest the importance of the Pacific Decadal Oscillation as possibly the greatest contributor. The two major maxima in the PDO index that occurred during the past century (~ 1940 and ~ 1990) are generally consistent with maxima and/or inflection points that occur both in the sub-regional and regional long-term trends. It has been difficult to associate specific ENSO episodes with the long-term trends. However, ENSO and the PDO are closely related. Recent modeling studies have shown that the PDO essentially owes its existence to ENSO. Thus, ENSO appears to be a major contributor to the long-term trends through its primary contribution to the PDO. Finally, spectral analysis also revealed the existence of an oscillation whose period is ~ 73 years, easily of sufficient length to influence the long-term trends. Climate-related oscillations in the range of 70–100 years are often associated with the Gleissberg sunspot cycle and this could be a contributing factor. The long-term trends are not necessarily a dominant feature in our data. However, had the observations been limited to the period from 1900 to ~ 1940, the trends would have been, without a doubt, dominant. Overall, the likely influence of the PDO on the observed long-term trends in SST must be emphasized. Finally, over the past 25 years there has been no significant change in surface temperature over the study area and this may be due in part to the cooling influence of the PDO since ~ 1990.
Author: Breaker, Loor, Carroll

Title: The 154-year record of sea level at San Francisco: Extracting the long-term trend, recent changes, and other tidbits,
Description: A data adaptive method called ensemble empirical mode decomposition (EEMD) is used to examine the 154-year record of monthly sea level at San Francisco. The mode that is lowest in frequency corresponds to the long-term trend. The next highest mode corresponds to an oscillation with a period of ~100 years and may be related to solar variability. When this mode is combined with the long-term trend, the rate of increase in sea level starts to decrease by ~1980. The next lower mode corresponds to interdecadal time scales and thus includes the Pacific Decadal Oscillation. When combined with the two lower modes, sea level itself starts to decrease by the mid-1990s. These results are consistent with the most recent results from the intergovernmental panel on climate change (IPCC), and may be the first obtained from a tidal record. Prior to conducting EEMD, corrections for glacial isostatic adjustment (GIA) and the inverse barometer (IB) effect were applied. The effect of applying the GIA correction was relatively small, but the IB correction reduced the slope of the long-term trend in sea level by almost 15%. This reduction is due to a long-term increase in the variance of sea level pressure. To determine if the 10-15 year ENSO modulation cycle could be detected from the decomposition we first compared the envelope from the mode associated with ENSO, with the two adjacent modes that were lower in frequency. Spectral analysis revealed no significant maxima in the ENSO mode envelope, but a major peak in the spectrum for the two adjacent modes, with a period of 12. 8 years. This is consistent with a local response to El Niño warming for the ENSO mode, but a non-local response for the two adjacent modes. A similar analysis was performed for the Southern Oscillation Index and a spectral maximum was found between 12 and 16 years, consistent with our non-local interpretation of the previous two modes. © 2010 Springer-Verlag., Cited By (since 1996):5, Oceanography, ,
Author: Breaker, Ruzmaikin
Date: 2011-01-01T00:00:00Z

Title: Development of a real-time regional ocean forecast system with application to a domain off the U.S east coast,
Description: This paper discusses the needs to establish a capability to provide real-time regional ocean forecasts and the feasibility of producing them on an operational basis. Specifically, the development of a Regional Ocean Forecast System using the Princeton Ocean Model (POM) as a prototype and its application to the East Coast of the U.S. are presented. The ocean forecasts are produced using surface forcing from the Eta model, the operational mesoscale weather prediction model at the National Centers for Environmental Prediction (NCEP). At present, the ocean forecast model, called the East Coast-Regional Ocean Forecast System (EC-ROFS) includes assimilation of sea surface temperatures from in situ and satellite data and sea surface height anomalies from satellite altimeters. Examples of forecast products, their, evaluation, problems that arose during the development of the system, and solutions to some of those problems are also discussed. Even though work is still in progress to improve the performance of EC-ROFS, it became clear that the forecast products which are generated can be used by marine forecasters if allowances for known model deficiencies are taken into account. The EC-ROFS became fully operational at NCEP in March 2002, and is the first forecast system of its type to become operational in the civil sector of the United States., Cited By (since 1996):2, Oceanography, ,
Author: Breaker, Rao, Kelley, Balasubramaniyan
Date: 2004-01-01T00:00:00Z

Title: What's happening in Monterey Bay on seasonal to interdecadal time scales,
Description: Daily observations of sea-surface temperature (SST) have been acquired at the southern end of Monterey Bay in Pacific Grove, California since 1919. It is one of the longest oceanographic records off the west coast of North America. The record is examined to determine the major sources of variability in Monterey Bay and beyond, on time scales from seasonal to interdecadal. On seasonal time scales, the spring transition to coastal upwelling, often a major event along the coast of central California, is not well-expressed inside the bay but is detectable, occurring, on average, between mid-March and mid-April. The onset of the Davidson Current in Monterey Bay is well-defined, occurring, on average, in mid-October, ±2-3 weeks. Intraseasonal changes also occur during the spring and summer that may correspond to intrusions of warmer offshore waters into Monterey Bay. Intraseasonal oscillations with periods in the range of 40-50 days occur in Monterey Bay, but compared to their signature along the open coast, their event-like behavior is modified. The annual cycle of surface temperature in Monterey Bay is asymmetric with seasonal warming occurring during the spring and summer, and cooling during the fall. This asymmetry is primarily due to the net surface heat exchange which is positive for most of the year, and, to a lesser extent, the influence cold upwelled waters that are advected into the bay during the spring and summer, observations supported by a simple model that combines both the net surface heat exchange and thermal advection. On interannual time scales, the influence of El Niño warming events is strong. A comparison with the Northern Oscillation Index (NOI) using Singular Spectrum Analysis (SSA), shows that the El Niño signal is often as strong in SST at Pacific Grove as it is in the NOI. On interdecadal time scales, the influence of the Pacific Decadal Oscillation (PDO) is also relatively strong in Monterey Bay, again based on SSA. The integrated anomaly was calculated from the record and reveals regime shifts in Monterey Bay that occurred in 1929, an event that was apparently regional in scale, reflecting a transition from unusually cold to warmer conditions, and the regime change in the PDO that occurred in 1976. Each regime change can be approximated by a step-wise increase in temperature. Finally, linear trends were estimated for the entire record (∼+0.01°C/year), and for the 72-year period from 1930 to 2001 (+0.0042°C/year), i.e., following the regional regime change in 1929. The estimated trend for the last 72 years is not statistically significant; however, it is in close agreement with the long-term trend for the Intergovernmental Panel on Climate Change (IPCC) record of global surface temperature that spans almost 140 years (∼+0.005°C/year). Although the long-term increase in SST at Pacific Grove appears to be consistent with global warming, the integrated anomaly suggests that temperature increases in Monterey Bay have occurred rather abruptly and thus it becomes more difficult to invoke the global warming scenario. Finally, based on the monthly averaged data, the annual cycle, El Niño warming episodes, the PDO, the long-term trend, and the semiannual cycle account for approximately 44%, 18%, 6%, 4%, and 3% of the total variance, respectively, in SST at Pacific Grove. © 2005 Elsevier Ltd. All rights reserved., Cited By (since 1996):11, Oceanography, CODEN: CSHRD, ,
Author: Breaker
Date: 2005-01-01T00:00:00Z

Title: A closer look at regime shifts based on coastal observations along the eastern boundary of the North Pacific,
Description: At least six regime shifts have been reported in the North Pacific since 1920. They occurred in 1925, 1939, 1946, 1976-1977, 1989 and 1999. The major change in 1976-1977 corresponds to a regime shift that is now widely accepted as a canonical event since it had a significant impact on virtually all climatic and ecosystem indicators. We seek to determine if daily sea surface temperature (SST) from Pacific Grove, in central California, and Scripps Pier, in southern California, and coastal observations from several other locations along the west coast of North America can be used to detect and resolve these events. Cumulative sums (CUSUMs) were initially calculated to enhance the detection process. The CUSUM trajectories during the 1976-1977 event at Pacific Grove and Scripps Pier were distinctive, highly correlated, and in phase. The turning point patterns from this event were then used to search for other events that have been reported since 1920. Turning point patterns very similar to the 1976-1977 event were detected in 1946 and 1989. The events in 1925 and 1939 were generally similar, but the CUSUM patterns for the event in 1999 departed significantly from the other events. Further examination of the 1976 and 1989 events revealed inflection points in the CUSUMs near the beginning and end of each transition that correspond to critical values or extrema in the original data. The inflection points and/or critical values provide an improved basis for determining the duration of these events. The robustness of the CUSUM approach for detecting regime shifts was examined by posing the inverse problem to determine if other possible regime changes could be detected that have not been previously reported. The period between 1946 and 1976 was examined, and one match in 1972 was found, which coincided with a large shift in the Aleutian Low Pressure Index. The CUSUM patterns associated with well-defined regime shifts may be essentially unique and thus useful in searching for other events. Whether the temperature ultimately increases or decreases following a regime shift is well-predicted by the sign of the CUSUM slope during an event. Testing regime shifts for statistical significance may be problematic, but our results suggest that when CUSUMs are employed, the detection problem becomes one that is more closely related to pattern recognition where other tests could be applied. CUSUMs often produce a distinct pattern that appears to be characteristic of regime shifts. During well-defined events such as those that occurred in 1946, 1976, and 1989, the CUSUM trajectories from Pacific Grove and Scripps Pier were highly synchronized and nearly identical in form. The CUSUM transformation allows us to identify, localize and observe how these events evolve. We have only been able to examine these events in such detail because daily observations from single locations were used. Based on the events we have examined, they have time scales that range from about 4-9 months. Salinity and sea level data were also employed in this study and were found to be less sensitive to the changes associated with regime shifts than SST. Regime shifts detected in CUSUMs of SST at two locations off Vancouver Island were found to be weaker in amplitude and less well-defined than those detected at Pacific Grove and Scripps Pier. However, they were in phase with the events observed further south. Establishing the connection between these results, and changes in the ecosystems of the North Pacific, should be given a high priority. Finally, the results of this study are related to decadal climate variability and provide additional insight into the nature of this phenomenon. © 2007 Elsevier Ltd. All rights reserved., Cited By (since 1996):8, Oceanography, ,
Author: Breaker
Date: 2007-01-01T00:00:00Z