DOCSLIB.ORG

Linking Surface Ocean and the Deep Sea

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Linking Surface Ocean and the Deep Sea Linking Surface Ocean and the Deep Sea. Richard Lampitt Southampton Oceanography Centre With many thanks to: AvanAntia Dave Billett Adrian Burd Maureen Conte Roger Francois Sus Honjo And all the other people from George Jackson whom I have stolen ideas, data Christine Klaas and images. Corinne Lequere Alex Mustard Susanne Neuer Uta Passow Katya Popova Olivier Ragueneau Richard Rivkin Ben Wigham 1 Primary 50m Production 500m Seabed “Linking Surface Ocean and the Deep Sea.” 1. Processes responsible 2. Temporal, Vertical and Geographic variations 3. Modelling approaches 4. Significance for (and of) benthic communities 5. The major achievements of JGOFS 6. Challenges ahead of us 2 Processes responsible for downward flux: Downwelling-DOM and POM Diffusion - DOM Gravitational sinking - POM Vertical migration -DOM and POM DOC (mMol) 20 30 40 50 60 70 80 90 100 0 100 200 300 400 500 600 Depth (meters) 700 800 900 1000 Richard Rivkin & Louis Legendre 3 What is POM? The “Fabulous Faecal Photo“ -- Debbie Steinberg 4 Bacterial Biomass (mg C l-1) 10-2 10-1 100 101 102 0 100 200 300 400 500 600 Depth (meters) 700 800 900 1000 Richard Rivkin & Louis Legendre Mesozooplankton: A copepod 5 Marine Snow Inanimate particles greater than 0.5mm diameter. The principal vehicles for downward particle flux 6 Zooplankter feeding on marine snow aggregate Lampitt 1995 Breakup of an aggregate By Euphausia pacifica (16 mm in length) Dilling and Alldredge 2000 7 Holo-Cam 2.4 m long In situ holographic Imaging 1.0 m dia. 2.3 tonnes 10 ns pulse 50 litre view Marine Snow particle As recorded by in situ holographic camera 8 Aggregation models: Stickiness Abundance Size Sinking rate “Linking Surface Ocean and the Deep Sea.” 1. Processes responsible 2. Temporal, Vertical and Geographic variations 3. Modelling approaches 4. Significance for (and of) benthic communities 5. The major achievements of JGOFS 6. Challenges ahead of us 9 Means of examination: Inferences from twilight zone oxygen consumption Inferences from primary production Measurement by sediment trap Inference from biological processes e.g. Gut evacuation rates, vertical migration Model output Oxygen uptake rate based on tritium-helium tracer dating of water masses => oxygen demand => Export flux ~3.8 mol m-2 a-1 or 45 g m-2 a-1 Jenkins 1998 10 Annual export of organic carbon as calculated from PTE model, temp and net PP. Laws et al 2000 Means of examination: Inferences from upper ocean processes Measurement by sediment trap Inference from biological processes e.g. Gut evacuation rates, vertical migration Model output 11 BGC Provinces (Longhurst 1995) Qualifying deep ocean sediment trap stations. 12 230Th Trapping Efficiency (%) 0 20 40 60 80 100 120 140 160 180 200 0 500 1000 1500 2000 2500 Depth (m) 3000 3500 4000 4500 5000 ESTOC OMEX-2 L1 OMEX-3 L2 OMEX-4 L3 WAST NABE 34 CAST NABE 48 EAST BOFS ESTOC Yu et al 2001 Scholten et al 2002 Downward particle flux in contrasting environments Apr Jun Aug Oct Dec Feb Apr 700 SW Monsoon 600 Western Indian Ocean /d) 2 3016m depth 500 (Haake et al 1993) 400 300 200 NE Monsoon 100 DW Flux (mg/m 0 100 150 200 250 300 350 400 450 500 Day Number 1986 Jan Mar May Jul Sep Nov Jan 700 600 Equatorial Pacific /d) 2 3618m depth 500 (Honjo et al 1995) 400 300 200 100 DW Flux (mg/m 0 0 50 100 150 200 250 300 350 400 Day Number 1992 13 High frequency variability and episodic flux"events” off Bermuda at 3200m ) 1 - d 3200 m 120 2 - 80 40 0 1980 1985 1990 1995 2000 Mass flux (mg m Maureen Conte BTM upper ocean records: Oct 96 - Jan 97 Depth (m) Fluorescence (V) Passage of a warm mesoscale feature over the time-series site (Dickey et al. 2001) 14 High frequency variability and episodic flux"events” off Bermuda at 3200m ) 1 - d 3200 m 120 2 - 80 40 0 1980 1985 1990 1995 2000 Mass flux (mg m Maureen Conte COLLECTION DATE 10/18- 11/2 - 11/18- 12/2 - 12 /18- 12/31 - 11/2 11/18 12/2 12/18 12/31 1/14 70 Org C flux (mg m Fluorescence Increase at BTM 3.5 ) 1 Nov 27 - 60 d 3.0 2 - 50 MASS 2.5 40 Organic 2.0 Carbon 30 1.5 - 20 2 1.0 d - 1 10 0.5 ) Mass flux (mg m 0 0.0 8 Phytosterols diols+ketols+acylglycerols 1) - 6 d alkenones (x2) 2 - PUFAs(x4) 4 g m m ( 2 Biomarker Flux Maureen Conte 15 Vertical trends Organic Carbon Flux (g/m2/y) 1 10 0 1000 2000 Depth (m) 3000 Martin et al 1987 0.858 4000 J=J100/((Z/100) ) 5000 Downward particulate flux as a function of depth 16 Export Ratio (POC FLUX/PP) 0,00 0,05 0,10 0,15 0 WML 1000 2000 Betzer Depth (m) Pace 3000 Berger ThisAntia study Suess 4000 Significance of the mixed layer depth Export Ratio (POC FLUX/PP) 0,00 0,05 0,10 0,15 0 1000 WML 2000 Betzer Depth (m) Pace 3000 Berger ThisAntia study Suess 4000 Significance of the mixed layer depth 17 THE MINERAL ASSOCIATION MODEL “Free” POC POC associated with ballast POC flux tightly linked to flux of ballast (Armstrong et al., 2002) Annual export of organic carbon as calculated from PTE model, temp and net PP. Laws et al 2000 18 Roger Francois Roger Francois 19 Transfer efficiency Roger Francois Increased settling velocity with depth (Berelson 2002) 20 Conclusion High latitudes have high export ratio but low transfer efficiency to the deep ocean. Explanations may lie in: the effect of SST, the mineral association of the organic carbon Sinking rate of particles Frequency of episodic events. Means of examination: Inferences from primary production Inferences from twilight zone oxygen consumption Measurement by sediment trap Inference from biological processes e.g. Gut evacuation rates, vertical migration Model output 21 Plankton diel vertical migration Alex Mustard (SOC) Potential mechanisms for material transport by plankton migration Surface 1: Mortality 2: Defecation Seasonal Thermocline 3: Excretion 4: Reproduction 5: Respiration Permanent Thermocline 22 Contribution of migrating plankton to downward flux 80 60 40 % Passive flux 20 0 HOT NABE EQPAC BATS (All) BATS (M-A) Subtrop. and trop. Atl From Steinberg modified by Ducklow et al. 2001 Primary 50m Production 500m Migration Advection Seabed 23 “Linking Surface Ocean and the Deep Sea.” 1. Processes responsible 2. Temporal, Vertical and Geographic variations 3. Modelling approaches 4. Significance for (and of) benthic communities 5. The major achievements of JGOFS 6. Challenges ahead of us 1D model: 24 Labile Phytoplankton Nitrate DON Ammonium Slow Bacteria Zooplankton Detritus Fast Detritus Ecosystem model based on Fasham and Evans 1995 The Porcupine Abyssal Plain Study site 60 1000m 2000m Rockall Bank 55 3000m Rockall Trough 200m 4000m 50 PAP JGOFS Porcupine Abyssal Plain 45 North Iberian 40 Abyssal Plain 35 Madeira Abyssal Plain 30 -25 -20 -15 -10 -5 0 West 25 Downward particle flux at the PAP time series site at 3000m depth (49o N 16.5o W) 16 Modelled flux 14 /d) Measured flux 2 12 10 8 6 4 2 Organic carbon Flux (mg/m 0 89 90 91 92 93 94 95 96 97 98 99 Year Lampitt et al 2001 Annual downward flux of organic carbon at 3000m depth. 3 Model Measured /y) 2 2 Flux (g/m 1 0 1988 1990 1992 1994 1996 1998 2000 Year Lampitt et al 2001 26 Global GCM’s with biogeochemistry The Seabed beneath: the ultimate sediment trap 27 The Porcupine Abyssal Plain Study site 60 1000m 2000m Rockall Bank 55 3000m Rockall Trough 200m 4000m 50 PAP JGOFS Porcupine Abyssal Plain 45 North Iberian 40 Abyssal Plain 35 Madeira Abyssal Plain 30 -25 -20 -15 -10 -5 0 West Time lapse photographs Of the seabed at 4000m on eastern side of PAP. Mound is 18cm across. Lampitt 1985 28 15cm long specimen of Benthogone rosea feeding on the phtodetrital layer at 2000m depth 16 100 14 Benthic phytodetritus /d) 2 12 80 10 60 8 6 40 4 20 % Benthic coverage 2 0 Organic carbon Flux (mg/m 0 89 90 91 92 93 94 95 96 97 98 99 Year Lampitt et al 2001 29 A movie of 9 months on the floor of the PAP Billett et al pers comm. Three specimens of the Holothurian Amperima rosea 30 600 Amperima rosea 500 400 300 200 100 2.2 6.7 3.9 Abundance (#/hectare) 0 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 Year Bett & Wigham Annual downward flux of organic carbon at 3000m depth. 3 Model Measured /y) 2 2 Flux (g/m 1 0 1988 1990 1992 1994 1996 1998 2000 Year Lampitt et al 2001 31 “Linking surface ocean and the deep sea” Major achievement of JGOFS 1. How to measure flux. 2. Temporal and geographical variability in flux and composition of material. 3. Ballast affects transfer efficiency. 4. Benthic communities are highly sensitive to upper ocean processes. 5. Models and data are converging. 6. Establishment of time series sites “Linking surface ocean and the deep sea” Future challenges 1. How does the “Martin curve” change in time and space? 2. What components of the midwater biosphere are the major players? 3. What is the effect of temporal variation in flux on aphotic communities? 4. Develop models. 5. Maintain time series sites. 32 A poor understanding of spatial and temporal distributions can have surprising and adverse effects.
Load more

Recommended publications
  • Marine Ecology Progress Series 600:21
    Vol. 600: 21–39, 2018 MARINE ECOLOGY PROGRESS SERIES Published July 30 https://doi.org/10.3354/meps12663 Mar Ecol Prog Ser OPENPEN ACCESSCCESS Short-term processing of ice algal- and phytoplankton- derived carbon by Arctic benthic communities revealed through isotope labelling experiments Anni Mäkelä1,*, Ursula Witte1, Philippe Archambault2 1School of Biological Sciences, University of Aberdeen, Aberdeen AB24 3UU, UK 2Département de biologie, Québec Océan, Université Laval, Québec, QC G1V 0A6, Canada ABSTRACT: Benthic ecosystems play a significant role in the carbon (C) cycle through remineral- ization of organic matter reaching the seafloor. Ice algae and phytoplankton are major C sources for Arctic benthic consumers, but climate change-mediated loss of summer sea ice is predicted to change Arctic marine primary production by increasing phytoplankton and reducing ice algal contributions. To investigate the impact of changing algal C sources on benthic C processing, 2 isotope tracing experiments on 13C-labelled ice algae and phytoplankton were conducted in the North Water Polynya (NOW; 709 m depth) and Lancaster Sound (LS; 794 m) in the Canadian Arc- tic, during which the fate of ice algal (CIA) and phytoplankton (CPP) C added to sediment cores was traced over 4 d. No difference in sediment community oxygen consumption (SCOC, indicative of total C turnover) between the background measurements and ice algal or phytoplankton cores was found at either site. Most of the processed algal C was respired, with significantly more CPP than CIA being released as dissolved inorganic C at both sites. Macroinfaunal uptake of algal C was minor, but bacterial assimilation accounted for 33−44% of total algal C processing, with no differences in bacterial uptake of CPP and CIA found at either site.
    [Show full text]
  • Phytoplankton As Key Mediators of the Biological Carbon Pump: Their Responses to a Changing Climate
    sustainability Review Phytoplankton as Key Mediators of the Biological Carbon Pump: Their Responses to a Changing Climate Samarpita Basu * ID and Katherine R. M. Mackey Earth System Science, University of California Irvine, Irvine, CA 92697, USA; [email protected] * Correspondence: [email protected] Received: 7 January 2018; Accepted: 12 March 2018; Published: 19 March 2018 Abstract: The world’s oceans are a major sink for atmospheric carbon dioxide (CO2). The biological carbon pump plays a vital role in the net transfer of CO2 from the atmosphere to the oceans and then to the sediments, subsequently maintaining atmospheric CO2 at significantly lower levels than would be the case if it did not exist. The efficiency of the biological pump is a function of phytoplankton physiology and community structure, which are in turn governed by the physical and chemical conditions of the ocean. However, only a few studies have focused on the importance of phytoplankton community structure to the biological pump. Because global change is expected to influence carbon and nutrient availability, temperature and light (via stratification), an improved understanding of how phytoplankton community size structure will respond in the future is required to gain insight into the biological pump and the ability of the ocean to act as a long-term sink for atmospheric CO2. This review article aims to explore the potential impacts of predicted changes in global temperature and the carbonate system on phytoplankton cell size, species and elemental composition, so as to shed light on the ability of the biological pump to sequester carbon in the future ocean.
    [Show full text]
  • Atlas of the Mediterranean Seamounts and Seamount-Like Structures
    Atlas of the Mediterranean Seamounts and Seamount-like Structures ULISSE 44 N JANUA S.LUCIA SPINOLA OCCHIALI ARAGÓ CALYPSO HILLS 42 CIALDI FELIBRES HILLS 42 TIBERINO ETRUSCHI LA RENAIXENÇA HILLS ALBANO MONTURIOL S.FELIÙ SMS DAUNO VERCELLI SALVÁ BRUTUS SPARTACUS CASSINIS EBRO BARONIE-K MARUSSI SECCHI-ADRIANO FARFALLE ALBATROS-CICERONE CRESQUES BERTRAN SELLI VENUS MORROT DE LA CIUTADELLA GORTANI SELE MONTE DELLA RONDINE TACITO SÓLLER ALABE DE MARCHI SIRENE SARDINIA D’ANCONA FLAVIO GIOIA AMENDOLARA 40 SALLUSTIO 40 MAGNAGHI POSEIDONE ROSSANO APHRODITI VAVILOV TIBULLO DIAMANTE MORROT CORNAGLIA V.EMANUELE CARIATI DE SA DRAGONERA MAJOR ISSEL PALINURO-STRABO OVIDIO VILADESTERS CATULLO GLAVKI ORAZIO MARSILI-PLINIO GLABRO ENOTRIO MANSEL JOHNSTON STONY SPONGE QUIRRA ENEA TITO LIVIO VIRGILIO ALCIONE AUGUSTO SES OLIVES GARIBALDI-GLAUCO LAMETINO 1 BROUKER JAUME 1 CORNACYA LAMETINO 2 COLOM TRAIANO LUCREZIO STOKES XABIA-IBIZA VESPASIANO LITERI SINAYA VALLSECA SISIFO EMILE BAUDOT GIULIO CESARE-CAESAR DREPANO ENARETE CASONI FONTSERÈ ICHNUSA IRA NAVTILOS CABO DE LA NAO AUSIÀS MARCH ANCHISE BELL GUYOT POMPEO PROMETEO MARTORELL ACESTE-TIBERIO EOLO FORMENTERA SOLUNTO ALKYONI FERRER SCUSO SAN VITO LOS MARTINES ALÍ BEI FINALE DON JUAN RESGUI RIBA SENTINELLE (SKERKI) BALIKÇI EL38 PLANAZO BIDDLECOMBE SILVIA 38 PLIS PLAS KEITH SECO DE PALOS ESTAFETTE HECATE ADVENTURE TALBOT TETIDE 170 km ÁGUILAS GALATEA PANTELLERIA ANFITRITE EMPEDOCLE PINNE ANTEO 2 KHAYR-AL-DIN CIMOTOE ANTEO 3 ABUBACER FOERSTNER NAMELESS PNT. E MADREPORE ANTEO 1 AVENZOAR PNT. CB CHELLA CABO DE GATA ANGELINA ALFEO SABINAR PNT. SW AVEMPACE-ALGARROBO MAIMONIDES RIDGE BANNOCK KOLUMBO DJIBOUTI-HERRADURA POLLUX BILIM ADRA-AVERROES MAIMONIDES BIRSA PNT. SE HERRADURA-DJIBOUTI LINOSA III AL-MANSOUR A EL SEGOVIANO DJIBOUTI VILLE ALBORÁN LINOSA I LINOSA II HÉSPERIDES HÉRCULES EL IDRISSI YUSUF KARPAS CATIFAS-W.
    [Show full text]
  • Ocean-Climate.Org
    ocean-climate.org THE INTERACTIONS BETWEEN OCEAN AND CLIMATE 8 fact sheets WITH THE HELP OF: Authors: Corinne Bussi-Copin, Xavier Capet, Bertrand Delorme, Didier Gascuel, Clara Grillet, Michel Hignette, Hélène Lecornu, Nadine Le Bris and Fabrice Messal Coordination: Nicole Aussedat, Xavier Bougeard, Corinne Bussi-Copin, Louise Ras and Julien Voyé Infographics: Xavier Bougeard and Elsa Godet Graphic design: Elsa Godet CITATION OCEAN AND CLIMATE, 2016 – Fact sheets, Second Edition. First tome here: www.ocean-climate.org With the support of: ocean-climate.org HOW DOES THE OCEAN WORK? OCEAN CIRCULATION..............................………….....………................................……………….P.4 THE OCEAN, AN INDICATOR OF CLIMATE CHANGE...............................................…………….P.6 SEA LEVEL: 300 YEARS OF OBSERVATION.....................……….................................…………….P.8 The definition of words starred with an asterisk can be found in the OCP little dictionnary section, on the last page of this document. 3 ocean-climate.org (1/2) OCEAN CIRCULATION Ocean circulation is a key regulator of climate by storing and transporting heat, carbon, nutrients and freshwater all around the world . Complex and diverse mechanisms interact with one another to produce this circulation and define its properties. Ocean circulation can be conceptually divided into two Oceanic circulation is very sensitive to the global freshwater main components: a fast and energetic wind-driven flux. This flux can be described as the difference between surface circulation, and a slow and large density-driven [Evaporation + Sea Ice Formation], which enhances circulation which dominates the deep sea. salinity, and [Precipitation + Runoff + Ice melt], which decreases salinity. Global warming will undoubtedly lead Wind-driven circulation is by far the most dynamic. to more ice melting in the poles and thus larger additions Blowing wind produces currents at the surface of the of freshwaters in the ocean at high latitudes.
    [Show full text]
  • Chapter 51. Biological Communities on Seamounts and Other Submarine Features Potentially Threatened by Disturbance
    Chapter 51. Biological Communities on Seamounts and Other Submarine Features Potentially Threatened by Disturbance Contributors: J. Anthony Koslow, Peter Auster, Odd Aksel Bergstad, J. Murray Roberts, Alex Rogers, Michael Vecchione, Peter Harris, Jake Rice, Patricio Bernal (Co-Lead members) 1. Physical, chemical, and ecological characteristics 1.1 Seamounts Seamounts are predominantly submerged volcanoes, mostly extinct, rising hundreds to thousands of metres above the surrounding seafloor. Some also arise through tectonic uplift. The conventional geological definition includes only features greater than 1000 m in height, with the term “knoll” often used to refer to features 100 – 1000 m in height (Yesson et al., 2011). However, seamounts and knolls do not appear to differ much ecologically, and human activity, such as fishing, focuses on both. We therefore include here all such features with heights > 100 m. Only 6.5 per cent of the deep seafloor has been mapped, so the global number of seamounts must be estimated, usually from a combination of satellite altimetry and multibeam data as well as extrapolation based on size-frequency relationships of seamounts for smaller features. Estimates have varied widely as a result of differences in methodologies as well as changes in the resolution of data. Yesson et al. (2011) identified 33,452 seamount and guyot features > 1000 m in height and 138,412 knolls (100 – 1000 m), whereas Harris et al. (2014) identified 10,234 seamount and guyot features, based on a stricter definition that restricted seamounts to conical forms. Estimates of total abundance range to >100,000 seamounts and to 25 million for features > 100 m in height (Smith 1991; Wessel et al., 2010).
    [Show full text]
  • Intern Report
    Insights from abyssal lebensspuren Jennifer Durden, University of Southampton, UK Mentors: Ken Smith, Jr., Christine Huffard, Katherine Dunlop Summer 2014 Keywords: lebensspuren, traces, abyss, megafauna, deposit-feeding, benthos, sediment ABSTRACT The seasonal input of food to the abyss impacts the benthic community, and changes to that temporal cycle, through changes to the climate and surface ocean conditions impact the benthic assemblage. Most of the benthic fauna are deposit feeders, and many leave traces (‘lebensspuren’) of their activity in the sediment. These traces provide an avenue for examining the temporal variations in the activity of these animals, with insights into the usage of food inputs to the system. Traces of a variety of functions were identified in photographs captured in 2011 and 2012 from Station M, a soft-sedimented abyssal site in the northeast Pacific. Lebensspuren creation, holothurian tracking, and lebensspuren duration were estimated from hourly time-lapse images, while trace densities, diversity and seabed coverage were assessed from photographs captured with a seabed- transiting vehicle. The creation rates and duration of traces on the seabed appeared to vary over time, and may have been related to food supply, as may tracking rates of holothurians. The density, diversity and seabed coverage by lebensspuren of different types varied with food supply, with different lag times for POC flux and salp coverage. These are interpreted to be due to selectivity of 1 deposit feeders, and different response times between trace creators. These variations shed light on the usage of food inputs to the abyss. INTRODUCTION Deep-sea benthic communities rely on a seasonal food supply of detritus from the surface ocean (Billett et al., 1983, Rice et al., 1986).
    [Show full text]
  • Drivers and Effects of Karenia Mikimotoi Blooms in the Western English Channel ⇑ Morvan K
    Progress in Oceanography 137 (2015) 456–469 Contents lists available at ScienceDirect Progress in Oceanography journal homepage: www.elsevier.com/locate/pocean Drivers and effects of Karenia mikimotoi blooms in the western English Channel ⇑ Morvan K. Barnes a,1, Gavin H. Tilstone a, , Timothy J. Smyth a, Claire E. Widdicombe a, Johanna Gloël a,b, Carol Robinson b, Jan Kaiser b, David J. Suggett c a Plymouth Marine Laboratory, Prospect Place, West Hoe, Plymouth PL1 3DH, UK b Centre for Ocean and Atmospheric Sciences, School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK c Functional Plant Biology & Climate Change Cluster, University of Technology Sydney, PO Box 123, Broadway, NSW 2007, Australia article info abstract Article history: Naturally occurring red tides and harmful algal blooms (HABs) are of increasing importance in the coastal Available online 9 May 2015 environment and can have dramatic effects on coastal benthic and epipelagic communities worldwide. Such blooms are often unpredictable, irregular or of short duration, and thus determining the underlying driving factors is problematic. The dinoflagellate Karenia mikimotoi is an HAB, commonly found in the western English Channel and thought to be responsible for occasional mass finfish and benthic mortali- ties. We analysed a 19-year coastal time series of phytoplankton biomass to examine the seasonality and interannual variability of K. mikimotoi in the western English Channel and determine both the primary environmental drivers of these blooms as well as the effects on phytoplankton productivity and oxygen conditions. We observed high variability in timing and magnitude of K. mikimotoi blooms, with abun- dances reaching >1000 cells mLÀ1 at 10 m depth, inducing up to a 12-fold increase in the phytoplankton carbon content of the water column.
    [Show full text]
  • Ridge Migration, Asthenospheric Flow and the Origin of Magmatic Segmentation in the Global Mid-Ocean Ridge System Richard F
    GEOPHYSICAL RESEARCH LETTERS, VOL. 31, L15605, doi:10.1029/2004GL020388, 2004 Ridge migration, asthenospheric flow and the origin of magmatic segmentation in the global mid-ocean ridge system Richard F. Katz, Marc Spiegelman, and Suzanne M. Carbotte Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York, USA Received 28 April 2004; accepted 7 July 2004; published 4 August 2004. [1] Global observations of mid-ocean ridge (MOR) [3] Previous authors have considered the possible effect bathymetry demonstrate an asymmetry in axial depth of ridge migration on MOR processes. A kinematic model across ridge offsets that is correlated with the direction of asthenospheric flow beneath a migrating ridge was used of ridge migration. Motivated by these observations, we by Davis and Karsten [1986] to explain the asymmetric have developed two-dimensional numerical models of distribution of seamounts about the Juan de Fuca ridge and asthenospheric flow and melting beneath a migrating MOR. by Schouten et al. [1987] to study the migration of non- The modification of the flow pattern produced by ridge transform offsets at spreading centers. Modeling studies migration leads to an asymmetry in melt production rates [Conder et al., 2002; Toomey et al., 2002] of the MELT on either side of the ridge. By coupling a simple parametric region of the EPR [Forsyth et al., 1998b] found the dynamic model of three dimensional melt focusing to our simulations, effect of ridge migration could produce an asymmetry in we generate predictions of axial depth differences across melt production, but not of the magnitude inferred from offsets in the MOR. These predictions are quantitatively across-ridge differences in P, S and Rayleigh wave veloc- consistent with the observed asymmetry.
    [Show full text]
  • Modelling an Alkenone-Like Proxy Record in the NW African Upwelling
    Biogeosciences, 3, 251–269, 2006 www.biogeosciences.net/3/251/2006/ Biogeosciences © Author(s) 2006. This work is licensed under a Creative Commons License. Modelling an alkenone-like proxy record in the NW African upwelling X. Giraud Research Center Ocean Margins, Universitat¨ Bremen, Postfach 330 440, 28 334 Bremen, Germany Received: 28 November 2005 – Published in Biogeosciences Discuss.: 27 January 2006 Revised: 16 May 2006 – Accepted: 30 May 2006 – Published: 21 June 2006 Abstract. A regional biogeochemical model is applied to temperature of these algae (Marlowe, 1984; Brassell et al., the NW African coastal upwelling between 19◦ N and 27◦ N 1986; Conte et al., 1998). Prahl et al. (1988) calibrated a lin- K0 to investigate how a water temperature proxy, alkenones, are ear relation between an unsaturation alkenone index (U37 ) produced at the sea surface and recorded in the slope sed- and the growth temperature of an E. huxleyi strain in cul- iments. The biogeochemical model has two phytoplankton ture experiments. It was then confirmed that this index could groups: an alkenone producer group, considered to be coc- be used in the open ocean to reconstruct SSTs from coretop colithophores, and a group comprising other phytoplankton. alkenone measurements (Muller¨ et al., 1998). K0 The Regional Ocean Modelling System (ROMS) is used to In order to be used as a paleotemperature proxy, the U37 simulate the ocean circulation and takes advantage of the K0 has to fulfil certain criteria. The stability of the U37 signal Adaptive Grid Refinement in Fortran (AGRIF) package to in the water and sedimentary diagenesis are still questions.
    [Show full text]
  • OCEAN SUBDUCTION Show That Hardly Any Commercial Enhancement Finney B, Gregory-Eaves I, Sweetman J, Douglas MSV Program Can Be Regarded As Clearly Successful
    1982 OCEAN SUBDUCTION show that hardly any commercial enhancement Finney B, Gregory-Eaves I, Sweetman J, Douglas MSV program can be regarded as clearly successful. and Smol JP (2000) Impacts of climatic change and Model simulations suggest, however, that stock- Rshing on PaciRc salmon over the past 300 years. enhancement may be possible if releases can be Science 290: 795}799. made that match closely the current ecological Giske J and Salvanes AGV (1999) A model for enhance- and environmental conditions. However, this ment potentials in open ecosystems. In: Howell BR, Moksness E and Svasand T (eds) Stock Enhancement requires improvements of assessment methods of and Sea Ranching. Blackwell Fishing, News Books. these factors beyond present knowledge. Marine Howell BR, Moksness E and Svasand T (1999) Stock systems tend to have strong nonlinear dynamics, Enhancement and Sea Ranching. Blackwell Fishing, and unless one is able to predict these dynamics News Books. over a relevant time horizon, release efforts are Kareiva P, Marvier M and McClure M (2000) Recovery not likely to increase the abundance of the target and management options for spring/summer chinnook population. salmon in the Columbia River basin. Science 290: 977}979. Mills D (1989) Ecology and Management of Atlantic See also Salmon. London: Chapman & Hall. Ricker WE (1981) Changes in the average size and Mariculture, Environmental, Economic and Social average age of PaciRc salmon. Canadian Journal of Impacts of. Salmonid Farming. Salmon Fisheries: Fisheries and Aquatic Science 38: 1636}1656. Atlantic; Paci\c. Salmonids. Salvanes AGV, Aksnes DL, FossaJH and Giske J (1995) Simulated carrying capacities of Rsh in Norwegian Further Reading fjords.
    [Show full text]
  • Diatom Fluxes to the Deep Sea in the Oligotrophic North Pacific Gyre at Station ALOHA
    MARINE ECOLOGY PROGRESS SERIES Published June 11 Mar Ecol Prog Ser Diatom fluxes to the deep sea in the oligotrophic North Pacific gyre at Station ALOHA Renate Scharek*, Luis M. Tupas, David M. Karl Department of Oceanography, School of Ocean and Earth Science and Technology, University of Hawaii, Honolulu, Hawaii 96822, USA ABSTRACT: Planktonic diatoms are important agents of vertical transport of photosynthetically fixed organic carbon to the ocean's interior and seafloor. Diatom fluxes to the deep sea were studied for 2 yr using bottom-moored sequencing sediment traps located in the vicinity of the Hawaii Ocean Time- series (HOT) program station 'ALOHA' (22'45'N, 158" W). The average flux of empty diatom frustules was around 2.8 X 10' cells m-' d ' in both years, except in late summer when it increased approximately 30-fold. Flux of cytoplasm-containing diatom cells was much lower (about 8 X 103 cells n1Y2 d") but increased 500-fold in late July 1992 and 1250-fold in August 1994. Mastogloia woodiana Taylor, Hemj- aulus hauckii Grunow and Rliizosolenia cf. clevei var. communis Sundstrom were the domlnant diatom species observed during the July 1992 event, with the former 2 species again dominant in August 1994. The 1994 summer flux event occurred about 3 wk after a documented bloom of H. hauckii and M. woodiana in the mixed-layer and a simultaneous increase in vertical flux of these species. This surface flux signal was clearly detectable at 4000 m, suggesting rapid settling rates. A further indication of very high sinking speeds of the diatoms was the much larger proportion of cytoplasm-containing cells in the bottom-moored traps during the 2 summer events.
    [Show full text]
  • Lecture 4: OCEANS (Outline)
    LectureLecture 44 :: OCEANSOCEANS (Outline)(Outline) Basic Structures and Dynamics Ekman transport Geostrophic currents Surface Ocean Circulation Subtropicl gyre Boundary current Deep Ocean Circulation Thermohaline conveyor belt ESS200A Prof. Jin -Yi Yu BasicBasic OceanOcean StructuresStructures Warm up by sunlight! Upper Ocean (~100 m) Shallow, warm upper layer where light is abundant and where most marine life can be found. Deep Ocean Cold, dark, deep ocean where plenty supplies of nutrients and carbon exist. ESS200A No sunlight! Prof. Jin -Yi Yu BasicBasic OceanOcean CurrentCurrent SystemsSystems Upper Ocean surface circulation Deep Ocean deep ocean circulation ESS200A (from “Is The Temperature Rising?”) Prof. Jin -Yi Yu TheThe StateState ofof OceansOceans Temperature warm on the upper ocean, cold in the deeper ocean. Salinity variations determined by evaporation, precipitation, sea-ice formation and melt, and river runoff. Density small in the upper ocean, large in the deeper ocean. ESS200A Prof. Jin -Yi Yu PotentialPotential TemperatureTemperature Potential temperature is very close to temperature in the ocean. The average temperature of the world ocean is about 3.6°C. ESS200A (from Global Physical Climatology ) Prof. Jin -Yi Yu SalinitySalinity E < P Sea-ice formation and melting E > P Salinity is the mass of dissolved salts in a kilogram of seawater. Unit: ‰ (part per thousand; per mil). The average salinity of the world ocean is 34.7‰. Four major factors that affect salinity: evaporation, precipitation, inflow of river water, and sea-ice formation and melting. (from Global Physical Climatology ) ESS200A Prof. Jin -Yi Yu Low density due to absorption of solar energy near the surface. DensityDensity Seawater is almost incompressible, so the density of seawater is always very close to 1000 kg/m 3.
    [Show full text]