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Maiti, K, Charette MA, Buesseler KO, Kahru M.  2013.  An inverse relationship between production and export efficiency in the Southern Ocean. Geophysical Research Letters. 40:1557-1561.   10.1002/grl.50219   AbstractWebsite

In the past two decades, a number of studies have been carried out in the Southern Ocean to look at export production using drifting sediment traps and thorium-234 based measurements, which allows us to reexamine the validity of using the existing relationships between production, export efficiency, and temperature to derive satellite-based carbon export estimates in this region. Comparisons of in situ export rates with modeled rates indicate a two to fourfold overestimation of export production by existing models. Comprehensive analysis of in situ data indicates two major reasons for this difference: (i) in situ data indicate a trend of decreasing export efficiency with increasing production which is contrary to existing export models and (ii) the export efficiencies appear to be less sensitive to temperature in this region compared to the global estimates used in the existing models. The most important implication of these observations is that the simplest models of export, which predict increase in carbon flux with increasing surface productivity, may require additional parameters, different weighing of existing parameters, or separate algorithms for different oceanic regimes.

Manzano-Sarabia, M, Salinas-Zavala CA, Kahru M, Lluch-Cota SE, Gonzalez-Becerril A.  2008.  The impact of the 1997-1999 warm-SST and low-productivity episode on fisheries in the southwestern Gulf of Mexico. Hydrobiologia. 610:257-267.   10.1007/s10750-008-9440-y   AbstractWebsite

Satellite-derived time-series of sea surface temperature (SST), chlorophyll a, and net primary productivity showed a period of warm SST and low productivity during 1997 and 1999 in the southwestern Gulf of Mexico followed by a period of colder than average SST (2000-2001). This shift between the warm and cold oceanic conditions might have caused significant changes in the structure of the ecosystem that is shown by changes in primary productivity and fishery landings between those periods.

Martinez-Fuentes, LM, Gaxiola-Castro G, Gomez-Ocampo E, Kahru M.  2016.  Effects of interannual events (1997-2012) on the hydrography and phytoplankton biomass of Sebastian Vizcaino Bay. Ciencias Marinas. 42:81-97.   10.7773/cm.v42i2.2626   AbstractWebsite

Sebastian Vizcaino Bay (Baja California Peninsula, Mexico) presents hydrographic conditions and phytoplankton biomass corresponding to a temperate/subtropical transition zone affected by large-scale tropical and subtropical events and those events originating in the subpolar Pacific region. Conditions in the first 50 m depth of the bay are mostly temperate (average temperature: 15.5 degrees C; average salinity: 33.6) and mesotrophic (phytoplankton biomass: >1 mg m(-3)). During spring and summer the bay is heavily influenced by the water transported by the California Current and the coastal upwelling generated off Punta Canoas. During the rest of the year the hydrography and phytoplankton biomass are mostly associated with subtropical conditions. The ENSO events arising in the period 1997-2012 affected the bay's water column. The extreme 1997-1998 El Nino generated increases of similar to 8 degrees C in temperature and similar to 0.8 in salinity. Local dynamic processes decreased the effects of moderate and weak El Nino events on phytoplankton biomass, with possible changes in the plankton functional groups. Due to the mostly temperate environment of the bay, the moderate 1998-2000 and 2010-2011 La Nina events did not generate a substantial change in the hydrography and phytoplankton biomass. However, the abundant subarctic water inflow in the period 2002-2006 abruptly decreased salinity and led to increased stratification of the water column and a reduction in phytoplankton chlorophyll.

McClatchie, S, Charter R, Watson W, Lo N, Hill K, Manzano-Sarabia M, Goericke R, Collins C, Bjorkstedt E, Schwing FB, Bograd SJ, Kahru M, Mitchell BG, Koslow JA, Ralston S, Field J, Peterson WT, Emmett R, Gomez-Valdes J, Lavaniegos BE, Caxiola-Castro G, Rogers-Bennet L, Gottschalck J, Heureux ML, Xue Y, Munger L, Campbell G, Merkens K, Camacho D, Havron A, Douglas A, Hildebrand J.  2009.  The state of the California Current, Spring 2008-2009: Cold conditions drive regional differences in coastal production. California Cooperative Oceanic Fisheries Investigations Reports. 50:43-68. AbstractWebsite

This report describes the state of the California Current system (CCS) between the springs of 2008 and 2009 based on observations taken along the west coast of North America The dominant forcing on the CCS during this time period were La Nina-type conditions that prevailed from the summer of 2007 through early 2009, transitioning to neutral El Nino-Southern Oscillation conditions in the spring of 2009 The Pacific Decadal Oscillation index was negative during this time period and its values had not returned to normal by the spring of 2009 The general effects on the California Current system were stronger thin normal southward winds and upwelling as well as generally colder than normal SST and shallow nitraclines, however, there were repot-ill differences Off alp California sea surface temperatures did not respond to the La Nina conditions, however, concentrations of chlorophyll a (Chl a) were significantly above normal, probably due to the anomalously high upwelling off Baja during most of the year Off southern California there was no clear evidence of increased primary or secondary production, despite observations that previous La Nina conditions affected mixed layer depth, temperatures, nutrients, and nitracline depths In both central and northern California and Oregon, stronger than normal upwelling increased primary production and prevented potential spawning of sardine north of San Francisco In central California the midwater fish community resembled that of recent cool years, and cover by kelp was much reduced along the coast Off Oregon there was evidence of increased abundance of boreal copepods, although the neritic boreal species did not appear to extend as far south is central California Current predictions are for cooler conditions to change to El Nino conditions by the end of 2009, these are expected to last through the Northern Hemisphere wintet of 2009-10

McClatchie, S, Goericke R, Koslow JA, Schwing FB, Bograd SJ, Charter R, Lo WWN, Hill K, Gottschalck J, L'Heureux M, Xue Y, Peterson WT, Emmett R, Collins C, Gaxiola-Castro G, Durazo R, Kahru M, Mitchell BG, Hyrenbach KD, Sydeman WJ, Bradley RW, Warzybok P, Bjorkstedt E.  2008.  THE STATE OF THE CALIFORNIA CURRENT, 2007-2008: LA NINA CONDITIONS AND THEIR EFFECTS ON THE ECOSYSTEM. California Cooperative Oceanic Fisheries Investigations Reports. 49:39-76. AbstractWebsite

The state of the California Current system (CCS) between Oregon and Baja California is summarized in this report, covering spring of 2007 to winter/spring 2008. The 2006-07 period began with moderate El Nino conditions which decayed rapidly in early 2007. By summer 2007, a moderate-to-strong La Nina had developed. The North Pacific sea surface temperature (SST) anomalies displayed a negative pattern of Pacific Decadal Oscillation with below-normal SSTs in the California Current and Gulf of Alaska consistent with this pattern. The region experienced anomalously strong southward coastal winds, leading to positive anomalies of the West Coast upwelling index, in Strong contrast with 2005. The 2007 upwelling season also began early (in contrast to delayed onset in 2005 and 2006) and remained unseasonably strong through May. The cumulative upwelling for the 2007 season was greater than normal in the southern portion of the California Current system. Despite the La Nina conditions, nitrate and chlorophyll concentrations off Oregon were about average in 2007. On the other hand, copepod biomass rebounded strongly in 2006 after the exceptionally low biomass in 2005, and copepod species richness in 2006 was low, also indicating transport Of sub-arctic water into the northern California Current in 2006-07, which is relatively productive but low in diversity. Anomalously high salinities at 200 in depth were also observed during CalCOFI and IMECOCAL cruises off Southern and Baja California. In the CalCOFI area, where there has been a general trend toward a deepening mixed layer, the mixed layer responded to this year's La Nina conditions by shoaling. Nitrate (but not silicate and phosphate) concentrations in the mixed layer were anomalously high, but chlorophyll concentrations were about average, except for spring 2007, which was one of the lowest values on record. Spring chlorophyll a concentrations are notably variable during La Ninas. In the northern California Current, forage fish and predatory fish abundance remained low in 2007. In the southern California Current, Pacific sardine (Sardinops sagax) larval abundance was relatively high and distributed in relation to the inner edge of the California Current and the edge of an eddy. Northern anchovy (Engraulis mordax) larvae were relatively low in abundance, apparently related to a large downwelling feature. Reproductive success of all six seabirds monitored on Farallon Island was recovering slowly this year, following the previous two disastrous seasons. However, cluster analysis indicated that reproductive success is still relatively low. The cold-water planktivorous auklets (Ptychoramphus aleuticus) continued to be found at high densities in Southern waters. Overall, the transition in 2007 to La Nina conditions appeared to contribute to average to above average productivity in the California Current, but the physical, chemical, and biological (phytoplankton, zooplankton, Fish, and seabird) indices of productivity were far from consistent.

McQuatters-Gollop, A, Reid PC, Edwards M, Burkill PH, Castellani C, Batten S, Gieskes W, Beare D, Bidigare RR, Head E, Johnson R, Kahru M, Koslow JA, Pena A.  2011.  Is there a decline in marine phytoplankton? Nature. 472:E6-E7.   10.1038/nature09950   AbstractWebsite

Phytoplankton account for approximately 50% of global primary production, form the trophic base of nearly all marine ecosystems, are fundamental in trophic energy transfer and have key roles in climate regulation, carbon sequestration and oxygen production. Boyce et al. compiled a chlorophyll index by combining in situ chlorophyll and Secchi disk depth measurements that spanned a more than 100-year time period and showed a decrease in marine phytoplankton biomass of approximately 1% of the global median per year over the past century. Eight decades of data on phytoplankton biomass collected in the North Atlantic by the Continuous Plankton Recorder (CPR) survey, however, show an increase in an index of chlorophyll (Phytoplankton Colour Index) in both the Northeast and Northwest Atlantic basinsFig. 1), and other long-term time series, including the Hawaii Ocean Time-series (HOT)8, the Bermuda Atlantic Time Series (BATS)8 and the California Cooperative Oceanic Fisheries Investigations (CalCOFI)9 also indicate increased phytoplankton biomass over the last 20–50 years. These findings, which were not discussed by Boyce et al.1, are not in accordance with their conclusions and illustrate the importance of using consistent observations when estimating long-term trends.

Melville, WK, Lenain L, Cayan DR, Kahru M, Kleissl JP, Linden PF, Statom NM.  2016.  The Modular Aerial Sensing System. Journal of Atmospheric and Oceanic Technology. 33:1169-1184.   10.1175/jtech-d-15-0067.1   AbstractWebsite

Satellite remote sensing has enabled remarkable progress in the ocean, earth, atmospheric, and environmental sciences through its ability to provide global coverage with ever-increasing spatial resolution. While exceptions exist for geostationary ocean color satellites, the temporal coverage of low-Earth-orbiting satellites is not optimal for oceanographic processes that evolve over time scales of hours to days. In hydrology, time scales can range from hours for flash floods, to days for snowfall, to months for the snowmelt into river systems. On even smaller scales, remote sensing of the built environment requires a building-resolving resolution of a few meters or better. For this broad range of phenomena, satellite data need to be supplemented with higher-resolution airborne data that are not tied to the strict schedule of a satellite orbit. To address some of these needs, a novel, portable, high-resolution airborne topographic lidar with video, infrared, and hyperspectral imaging systems was integrated. The system is coupled to a highly accurate GPS-aided inertial measurement unit (GPS IMU), permitting airborne measurements of the sea surface displacement, temperature, and kinematics with swath widths of up to 800 m under the aircraft, and horizontal spatial resolution as low as 0.2 m. These data are used to measure ocean waves, currents, Stokes drift, sea surface height (SSH), ocean transport and dispersion, and biological activity. Hydrological and terrestrial applications include measurements of snow cover and the built environment. This paper describes the system, its performance, and present results from recent oceanographic, hydrological, and terrestrial measurements.

Mitchell, BG, Bricaud A, Carder K, Cleveland J, Ferri GM, Gould RJ, Kahru M, Kishino M, Maske H, Moisan T, Moore L, Nelson NB, Phinney D, Reynolds RA, Sosik HM, Stramski D, Tassan S, Trees C, Weidemann A, Wieland JD, Vodacek A.  2000.  Determination of spectrl absorption coefficients of particles, dissolved material and phytoplankton for discrete water samples. Ocean optics protocols for satellite ocean color sensor validation, Revision 2, NASA Technical Memorandum 2000-209966m/cgaoer 12 m o. ( Fargion GS, Mueller JL, McClain CR, Eds.).:125-153., Greenbelt, Md.: National Aeronautics and Space Administration, Goddard Space Flight Center Abstract

"This document stipulates protocols for measuring bio-optical and radiometric data for the Senor Inter comparison and Merger for Biological and Interdisciplinary Oceanic Studies (SIMBIOS) Project activities and algorithm development. This document supersedes the earlier version published as Volume 25 in the SeaWiFS Technical report series ..."

Mitchell, BG, Kahru M.  2009.  Bio-optical algorithms for ADEOS-2 GLI. Journal of The Remote Sensing Society of Japan. 29:80-85. Abstract

Empirical bio-optical algorithms developed for GLI are described. These algorithms can be used to retrieve in-water properties from GLI normalized water leaving radiances in temperate Case + waters. The OC. Chl-a algorithm uses the maximum band ratio switching procedure for bands that do not saturate over the ocean. GLI is the only ocean color sensor that has ultra-violet (UV) bands and we developed an experimental red tide UV index for the early detection of dinoflagellate blooms. The red tide index uses the increased absorption of UV light by mycosporine-like amino-acids (MAAs). A special version of the Chl-a algorithm was developed for the Southern Ocean Case + waters. The standard algorithms cannot be applied to turbid near-shore waters, e.g. o# Korea and Hong Kong where bio-optical characteristics deviate drastically from Case + characteristics. Developing new and improved algorithms for Case , waters is a major challenge in bio-optical oceanography.

Mitchell, BG, Kahru M.  1998.  Algorithms for SeaWiFS standard products developed with the CalCOFI big-optical data set. California Cooperative Oceanic Fisheries Investigations Reports. 39:133-147. AbstractWebsite

Funding from NASA's Ocean Biogeochemistry Program and the Goddard Space Flight Center SeaWiFS Project was used to implement an ocean optics program as part of the routine cruises of the California Cooperative Oceanic Fisheries Investigations (CalCOFI). Since August 1993, data from more than 300 bio-optical stations have been acquired, merged with complementary data, and made available for developing remote sensing algorithms. The profiling instrument consisted of a Biospherical Instruments, Inc. MER-2040/2041 radiometer integrated with CTD probes, a transmissometer, and a fluorometer. A detailed calibration time series of the radiance and irradiance sensors has been maintained to ensure maximum accuracy. The data set has been used to develop empirical algorithms for Sea WiFS standard products including chlorophyll a (chl a), "CZCS pigments," and diffuse attenuation coefficient K-d(490). Algorithms using cubic regressions of remote sensing reflectance (R-rs) ratios provided the best estimation of chi a and pigments over the full range of chl a (0.05-22.3 mg m(-3)). Multiple linear regressions of multiple-band ratios proved to be less robust. Relationships between spectral K and chi a suggest that previous K algorithms may have errors due to estimates of pure-water absorption.

Mitchell, BG, Kahru M, Wieland JD, Stramska M.  2002.  Determination of spectral absorption coefficients of particles, dissolved material and phytoplankton for discrete water samples. Ocean optics protocols for satellite ocean color sensor validation, revision 3. 2( Mueller JL, Fargion GS, Eds.)., Greenbelt, Md.: National Aeronautics and Space Administration, Goddard Space Flight Center Abstract
Murakami, H, Sasaoka K, Hosoda K, Fukushima H, Toratani M, Frouin R, Mitchell BG, Kahru M, Deschamps PY, Clark D, Flora S, Kishino M, Saitoh S, Asanuma I, Tanaka A, Sasaki H, Yokouchi K, Kiyomoto Y, Saito H, Dupouy C, Siripong A, Matsumura S, Ishizaka J.  2006.  Validation of ADEOS-II GLI ocean color products using in-situ observations. Journal of Oceanography. 62:373-393.   10.1007/s10872-006-0062-6   AbstractWebsite

The Global Imager (GLI) aboard the Advanced Earth Observing Satellite-II (ADEOS-II) made global observations from 2 April 2003 to 24 October 2003. In cooperation with several institutes and scientists, we obtained quality controlled match-ups between GLI products and in-situ data, 116 for chlorophyll-a concentration (CHLA), 249 for normalized water-leaving radiance (nLw) at 443 nm, and 201 for aerosol optical thickness at 865 nm (Tau_865) and Angstrom exponent between 520 and 865 nm (Angstrom). We evaluated the GLI ocean color products and investigated the causes of errors using the match-ups. The median absolute percentage differences (MedPD) between GLI and in-situ data were 14.1-35.7% for nLws at 380-565 nm 52.5-74.8% nLws at 625-680 nm, 47.6% for Tau_865, 46.2% for Angstrom, and 46.6% for CHLA, values that are comparable to the ocean-color products of other sensors. We found that some errors in GLI products are correlated with observational conditions; nLw values were underestimated when nLw at 680 nm was high, CHLA was underestimated in absorptive aerosol conditions, and Tau_865 was overestimated in sunglint regions. The error correlations indicate that we need to improve the retrievals of the optical properties of absorptive aerosols and seawater and sea surface reflection for further applications, including coastal monitoring and the combined use of products from multiple sensors.