86 research outputs found
Bio-Optical Measurements in Upwelling Ecosystems in Support of SIMBIOS
No full textThe upwelling region of the equatorial Pacific Ocean, which spans one quarter of the earth s circumference, strongly impacts global biogeochemistry. This upwelling system has significant implications for global CO2 fluxes (Tans et al., 1990; Takahashi et al., 1997; Feely et al., 1999), as well as primary and secondary production (Chavez and Barber, 1987; Chavez and Toggweiler, 1995; Chavez et al., 1996; Dugdale and Wilkerson, 1998; Chavez et al., 1999; Strutton and Chavez, 2000). In addition, the region represents a vast oceanic (case 1) region over which validation data for SeaWiFS are needed. This project consists of an optical mooring program and cruise-based measurements focused on measuring biological and chemical variability in the equatorial Pacific and obtaining validation data for SeaWiFS
Satellite-based prediction of pCO2 in coastal waters of the eastern North Pacific
No full textContinental margin carbon cycling is complex, highly variable over a range of space and time scales, and forced by multiple physical and biogeochemical drivers. Predictions of globally significant air–sea CO2 fluxes in these regions have been extrapolated based on very sparse data sets. We present here a method for predicting coastal surface-water pCO2 from remote-sensing data, based on self organizing maps (SOMs) and a nonlinear semi-empirical model of surface water carbonate chemistry. The model used simple empirical relationships between carbonate chemistry (total dissolved carbon dioxide (TCO2) and alkalinity (TAlk)) and satellite data (sea surface temperature (SST) and chlorophyll (Chl)). Surface-water CO2 partial pressure (pCO2) was calculated from the empirically-predicted TCO2 and TAlk. This directly incorporated the inherent nonlinearities of the carbonate system, in a completely mechanistic manner. The model’s empirical coefficients were determined for a target study area of the central North American Pacific continental margin (22–50°N, within 370 km of the coastline), by optimally reproducing a set of historical observations paired with satellite data. The model-predicted pCO2 agreed with the highly variable observations with a root mean squared (RMS) deviation of 0.8 (r = 0.81; r2 = 0.66). This level of accuracy is a significant improvement relative to that of simpler models that did not resolve the biogeochemical sub-regions or that relied on linear dependences on input parameters. Air–sea fluxes based on these pCO2 predictions and satellite-based wind speed measurements suggest that the region is a ∼14 Tg C yr−1 sink for atmospheric CO2 over the 1997–2005 period, with an approximately equivalent uncertainty, compared with a ∼0.5 Tg C yr−1 source predicted by a recent bin-averaging and interpolation-based estimate for the same area.Fil: Hales, Burke. State University of Oregon; Estados UnidosFil: Strutton, Peter G.. University Of Tasmania; AustraliaFil: Saraceno, Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmosfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmosfera; ArgentinaFil: Letelier, Ricardo. State University of Oregon; Estados UnidosFil: Takahashi, Taro. Lamont-Doherty Earth Observatory; Estados UnidosFil: Feely, Richard. National Oceanic and Atmospheric Administration. Pacific Marine Environmental Laboratory; Estados UnidosFil: Sabine, Christopher. National Oceanic and Atmospheric Administration. Pacific Marine Environmental Laboratory; Estados UnidosFil: Chavez, Francisco. Monterey Bay Aquarium Research Institute; Estados Unido
Sounds of fishes in a Posidonia seagrass meadow (Ustica Island, 1999)
No full text<p>These fish sound recordings are issued from the original acoustic dataset of USTICA 99 experiment described in:</p>
<p>Chapter 5. Acoustic Remote Sensing of Photosynthetic Activity in Seagrass Beds</p>
<p>Jean-Pierre Hermand</p>
<p>Handbook of Scaling Methods in Aquatic Ecology<br>
Measurement, Analysis, Simulation<br>
Edited by Peter G. Strutton and Laurent Seuront<br>
CRC Press 2003<br>
Pages 65–96<br>
Print ISBN: 978-0-8493-1344-8<br>
eBook ISBN: 978-0-203-48955-0<br>
DOI: 10.1201/9780203489550.ch5</p>
<p> </p>
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Iron links river runoff and shelf width to phytoplankton biomass along the U.S. West Coast
No full textA poleward increase in phytoplankton biomass along
the West Coast of North America has been attributed to
increasing river runoff towards the north. We combine
streamflow and shelf width data with satellite-derived
estimates of phytoplankton biomass to quantify the
relationship between these variables. We find that a
combination of winter streamflow and shelf width can
account for over 80% of the spatial variance in summer
chlorophyll within 50 km of the coast. At a given
location, interannual variability in streamflow is not
associated with interannual variability in chlorophyll.
We attribute these relationships to the role of rivers as
suppliers of the micronutrient iron, and the role of the
shelf as a ‘capacitor’ for riverine iron, charging during
the high-flow winter season and discharging during the
upwelling season. Data from the Oregon shelf confirm
that, during winter, a significant fraction of riverine iron
escapes the estuary and reaches the coastal ocean.Keywords: iron, runoff, productivit
Regional variations in the influence of mesoscale eddies on near‐surface chlorophyll
No full textAuthor Posting. © American Geophysical Union, 2014. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 119 (2014): 8195–8220, doi:10.1002/2014JC010111.Eddies can influence biogeochemical cycles through a variety of mechanisms, including the excitation of vertical velocities and the horizontal advection of nutrients and ecosystems, both around the eddy periphery by rotational currents and by the trapping of fluid and subsequent transport by the eddy. In this study, we present an analysis of the influence of mesoscale ocean eddies on near-surface chlorophyll (CHL) estimated from satellite measurements of ocean color. The influences of horizontal advection, trapping, and upwelling/downwelling on CHL are analyzed in an eddy-centric frame of reference by collocating satellite observations to eddy interiors, as defined by their sea surface height signatures. The influence of mesoscale eddies on CHL varies regionally. In most boundary current regions, cyclonic eddies exhibit positive CHL anomalies and anticyclonic eddies contain negative CHL anomalies. In the interior of the South Indian Ocean, however, the opposite occurs. The various mechanisms by which eddies can influence phytoplankton communities are summarized and regions where the observed CHL response to eddies is consistent with one or more of the mechanisms are discussed. This study does not attempt to link the observed regional variability definitively to any particular mechanism but provides a global overview of how eddies influence CHL anomalies.This work was funded by NASA grants NNX08AI80G, NNX08AR37G, and NNX10AO98G. DJM gratefully acknowledges NASA grant NNX13AE47G and NSF grant OCE-1048897.2015-06-0
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Seasonal cycle of surface ocean pCO₂ on the Oregon shelf
No full textPrevious work has shown that the Oregon shelf is a sink for atmospheric carbon dioxide (CO₂) during the upwelling season; however, until now, summertime variability in CO₂ exchange and sign of the flux for the rest of the year were unknown. Observations of the partial pressure of CO₂ (pCO₂) in surface waters from August 2007 to May 2010 from ships and a buoy were used with historical data to produce a composite seasonal cycle for the central Oregon midshelf. These data indicate that the region is highly variable, at times being either a sink or strong source for atmospheric CO₂. Interannual wind variability was an important determining factor in shaping the sink/source nature of this system. Late summer and early autumn was most variable relative to the rest of the year. Winter pCO₂ was near or slightly below atmospheric levels. Strong shelf-wide undersaturated conditions were first observed in early spring and lasted until the upwelling season became developed. Peak upwelling season pCO₂ ranged from 1000 μatm. In July 2008, ship and buoy data revealed previously unobserved high-pCO₂ waters (∼1000 μatm) at the surface. These conditions persisted for nearly 2 months and drove this system to be only a weak net annual atmospheric CO₂ sink of −0.3 ± 6.8 mol m⁻² yr⁻¹. These data showed, for the first time, the seasonal cycle of surface ocean pCO₂ on the central Oregon midshelf and the impact of heretofore undocumented pCO₂ levels on an estimate of sea-air CO₂ flux for this region.This is the publisher's final pdf. The published article is copyrighted by American Geophysical Union and can be found at: http://www.agu.org/journals/jc
Primary productivity in the equatorial Pacific during the 1997-98 El Niño
No full textShipboard biological and physical measurements made during 1996, 1997, and 1998 in the equatorial Pacific are used to quantify the effect of the 1997–1998 El Niño on the phytoplankton community. This El Niño was by some measures the strongest ever observed and resulted in extremely low phytoplankton biomass and productivity throughout this normally moderately productive region. At the height of the event in late 1997 to early 1998, in the central Pacific, nitrate was absent throughout the entire euphotic zone (∼100 m), resulting in chlorophyll concentrations (0.05 μgL−1) that were among the lowest ever observed in the region and rates of primary production (∼0.41 g C m−2 d−1) that were approximately half the climatological mean. These conditions persisted until May 1998 when the trade winds resumed and upwelling, with its associated supply of nutrients, was restored along the equatorial Pacific. The phytoplankton community quickly recovered, and by June 1998, nitrate, chlorophyll, and primary productivity levels were comparable to, or in excess of, their respective climatological means.</p
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Silicon biogeochemistry in the open-ocean surface waters : insights from the Sargasso Sea and equatorial Pacific
No full textDiatoms are a ubiquitous group of plankton responsible for 20-40% of oceanic
primary production, and a higher fraction of organic matter export to the ocean
interior. Diatoms actively transport dissolved inorganic silicon into their cells, and
through the process of silicification (i.e. biogenic silica production) they build tough
and intricate shells, known as frustules. With a global distribution and the ability to
persist in high numerical abundances, diatoms dominate the biological cycling of Si in
the oceans. The biogeochemical cycling of Si has been well studied in the coastal
ocean, specifically in upwelling regions where diatoms are generally the dominant
phytoplankton group. However, much less is known about the role diatoms play in the
open ocean; which comprises the vast majority of the oceanic surface area. Outside of
the Southern Ocean, only 11 studies (prior to 2003) directly examined surface-water Si
biogeochemistry in the open ocean. Current knowledge about Si biogeochemistry in
the open ocean suffers from what can only be described as gross under-sampling. This
dissertation reports on the surface-water Si biogeochemistry in two open-ocean
regions: the northwestern Sargasso Sea and the eastern equatorial Pacific. The three
research chapters are linked by the examination of spatial or temporal variability in
surface-water Si biogeochemistry. Chapters 2 and 4 examine scales of temporal
variability in Si biogeochemistry in the Sargasso Sea. The results demonstrate that
biogenic silica concentrations, and presumably Si biogeochemical processes, vary on daily, seasonal, multi-year (e.g. ~3-4 years), and decadal time scales. In Chapter 3
data were gathered over a ~2.6x106 km2 area (i.e. larger than the Bering Sea) in the
equatorial Pacific. Within that area biogenic silica production showed little spatial or
temporal variability. Additionally, the estimated contribution to new production
(productivity supporting the export of organic matter to the ocean interior) by diatoms
in this region was 4-10 times higher than the diatom contribution to total autotrophic
biomass
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