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Inferences on Potential Seamount Locations from Mid-Resolution
T. Morato and D. Pauly (eds.), Seamounts: Biodiversity and Fisheries, Page 7 INFERENCES ON POTENTIAL SEAMOUNT LOCATIONS FROM MID- RESOLUTION BATHYMETRIC DATA Adrian Kitchingman and Sherman Lai Fisheries Centre, The University of British Columbia. 2259 Lower Mall, Vancouver, B.C., V6T 1Z4, Canada [email protected]; [email protected] ABSTRACT Seamounts are underwater volcanoes that did not grow tall enough to break to the sea surface and turn into islands. Once formed, seamounts tend to gradually sink under their own weight and the subsidence of the lithosphere. The ocean floor is littered with these former seamounts, here called ‘seamounds’. Seamounts occur throughout the world's oceans, but their number (which may surpass 50,000) is difficult to estimate, even roughly, because it depends on the resolution of the bathymetric map used and the specific definition of a seamount used, i.e., the limits used to distinguish between seamounts and seamounds. Here, the locations of a subset of the seamounts of the world were identified using two algorithms relying on the depth differences between adjacent cells of a digital global elevation map distributed by the U.S. National Oceanographic and Atmospheric Agency (NOAA). The overlap of both algorithms resulted in a set of about 14,000 seamounts, but a different number would have been found had we used different thresholds. Known seamount locations supplied by NOAA and SeamountsOnline (http://seamounts.sdsc.edu) were compared against the corresponding seamounts located by the study, which led to some degree of ground-truthing. The coordinates of the seamounts identified in this study are available on the CD-ROM attached to this report, and on http://www.seaaroundus.org. -
A Numerical Study of the Long- and Short-Term Temperature Variability and Thermal Circulation in the North Sea
JANUARY 2003 LUYTEN ET AL. 37 A Numerical Study of the Long- and Short-Term Temperature Variability and Thermal Circulation in the North Sea PATRICK J. LUYTEN Management Unit of the Mathematical Models, Brussels, Belgium JOHN E. JONES AND ROGER PROCTOR Proudman Oceanographic Laboratory, Bidston, United Kingdom (Manuscript received 3 January 2001, in ®nal form 4 April 2002) ABSTRACT A three-dimensional numerical study is presented of the seasonal, semimonthly, and tidal-inertial cycles of temperature and density-driven circulation within the North Sea. The simulations are conducted using realistic forcing data and are compared with the 1989 data of the North Sea Project. Sensitivity experiments are performed to test the physical and numerical impact of the heat ¯ux parameterizations, turbulence scheme, and advective transport. Parameterizations of the surface ¯uxes with the Monin±Obukhov similarity theory provide a relaxation mechanism and can partially explain the previously obtained overestimate of the depth mean temperatures in summer. Temperature strati®cation and thermocline depth are reasonably predicted using a variant of the Mellor±Yamada turbulence closure with limiting conditions for turbulence variables. The results question the common view to adopt a tuned background scheme for internal wave mixing. Two mechanisms are discussed that describe the feedback of the turbulence scheme on the surface forcing and the baroclinic circulation, generated at the tidal mixing fronts. First, an increased vertical mixing increases the depth mean temperature in summer through the surface heat ¯ux, with a restoring mechanism acting during autumn. Second, the magnitude and horizontal shear of the density ¯ow are reduced in response to a higher mixing rate. -
World Ocean Thermocline Weakening and Isothermal Layer Warming
applied sciences Article World Ocean Thermocline Weakening and Isothermal Layer Warming Peter C. Chu * and Chenwu Fan Naval Ocean Analysis and Prediction Laboratory, Department of Oceanography, Naval Postgraduate School, Monterey, CA 93943, USA; [email protected] * Correspondence: [email protected]; Tel.: +1-831-656-3688 Received: 30 September 2020; Accepted: 13 November 2020; Published: 19 November 2020 Abstract: This paper identifies world thermocline weakening and provides an improved estimate of upper ocean warming through replacement of the upper layer with the fixed depth range by the isothermal layer, because the upper ocean isothermal layer (as a whole) exchanges heat with the atmosphere and the deep layer. Thermocline gradient, heat flux across the air–ocean interface, and horizontal heat advection determine the heat stored in the isothermal layer. Among the three processes, the effect of the thermocline gradient clearly shows up when we use the isothermal layer heat content, but it is otherwise when we use the heat content with the fixed depth ranges such as 0–300 m, 0–400 m, 0–700 m, 0–750 m, and 0–2000 m. A strong thermocline gradient exhibits the downward heat transfer from the isothermal layer (non-polar regions), makes the isothermal layer thin, and causes less heat to be stored in it. On the other hand, a weak thermocline gradient makes the isothermal layer thick, and causes more heat to be stored in it. In addition, the uncertainty in estimating upper ocean heat content and warming trends using uncertain fixed depth ranges (0–300 m, 0–400 m, 0–700 m, 0–750 m, or 0–2000 m) will be eliminated by using the isothermal layer. -
Seafloor Mapping of the Continental Slope of the U.S. Atlantic Margin to Study Submarine Landslides That Could Trigger Tsunamis
Seafloor Mapping of the Continental Slope of the U.S. Atlantic Margin to Study Submarine Landslides that Could Trigger Tsunamis An additional Report to the Nuclear Regulatory Commission Job Code Number: N6480 By Atlantic and Gulf of Mexico Tsunami Hazard Assessment Group Seafloor Mapping of the Continental Slope of the U.S. Atlantic Margin to Study Submarine Landslides that Could Trigger Tsunamis An Additional Report to the Nuclear Regulatory Commission By Atlantic and Gulf of Mexico Tsunami Hazard Assessment Group: Uri ten Brink, David Twichell, Jason Chaytor, Bill Danforth, Brian Andrews, and Elizabeth Pendleton U.S. Geological Survey, Woods Hole Coastal and Marine Science Center, Woods Hole, Massachusetts, USA This reports provides additional information to the report Evaluation of Tsunami Sources with Potential to Impact the U.S. Atlantic and Gulf Coasts, submitted to the Nuclear Regulatory Commission on August 22, 2008. October 15, 2010 NOTICE FROM USGS This publication was prepared by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, make any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed in this report, or represent that its use would not infringe privately owned rights. Reference therein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. Any views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. -
Shear Dispersion in the Thermocline and the Saline Intrusion$
Continental Shelf Research ] (]]]]) ]]]–]]] Contents lists available at SciVerse ScienceDirect Continental Shelf Research journal homepage: www.elsevier.com/locate/csr Research papers Shear dispersion in the thermocline and the saline intrusion$ Hsien-Wang Ou a,n, Xiaorui Guan b, Dake Chen c,d a Division of Ocean and Climate Physics, Lamont-Doherty Earth Observatory, Columbia University, 61 Rt. 9W, Palisades, NY 10964, United States b Consultancy Division, Fugro GEOS, 6100 Hillcroft, Houston, TX 77081, United States c Lamont-Doherty Earth Observatory, Columbia University, United States d State Key Laboratory of Satellite Ocean Environment Dynamics, Hangzhou, China article info abstract Article history: Over the mid-Atlantic shelf of the North America, there is a pronounced shoreward intrusion of the Received 11 March 2011 saltier slope water along the seasonal thermocline, whose genesis remains unexplained. Taking note of Received in revised form the observed broad-band baroclinic motion, we postulate that it may propel the saline intrusion via the 15 March 2012 shear dispersion. Through an analytical model, we first examine the shear-induced isopycnal diffusivity Accepted 19 March 2012 (‘‘shear diffusivity’’ for short) associated with the monochromatic forcing, which underscores its varied even anti-diffusive short-term behavior and the ineffectiveness of the internal tides in driving the shear Keywords: dispersion. We then derive the spectral representation of the long-term ‘‘canonical’’ shear diffusivity, Saline intrusion which is found to be the baroclinic power band-passed by a diffusivity window in the log-frequency Shear dispersion space. Since the baroclinic power spectrum typically plateaus in the low-frequency band spanned by Lateral diffusion the diffusivity window, canonical shear diffusivity is simply 1/8 of this low-frequency plateau — Isopycnal diffusivity Tracer dispersion independent of the uncertain diapycnal diffusivity. -
Importance of Seamount-Like Features for Conserving Mediterranean Marine Habitats and Threatened Species
Nº. 1105 IMPORTANCE OF SEAMOUNT-LIKE FEATURES FOR CONSERVING MEDITERRANEAN MARINE HABITATS AND THREATENED SPECIES Ricardo Aguilar, Xavier Pastor, Silvia García & Pilar Marín Oceana. Leganitos, 47 - 28013 Madrid. Spain - *[email protected] INTRODUCTION HABITAT LOCATION MAIN SPECIES 16 of the more than 200 seamount‑like peaks in the Mediterranean1 have been observed using ROV. Coral reefs 4, 5, 6, 7 Lophelia pertusa, Madrepora oculata Desmophyllum dianthus, Stenocyathus vermiformis, The findings, which include carnivorous sponges, elasmobranches, coral gardens, sponge aggregations, Cold water corals All sites Caryophyllia spp. Pourtalosmilia anthophyllites, Javania caileti, coralligenous beds, as well as species new to science like the giant foraminifera Spiculosiphon oceana, Anomocora fecunda, Dendrophyllia spp. Paramuricea spp., Eunicella spp., Viminella flagellum, or new to the Mediterranean, like the scleractinian Anomocora fecunda, underscore the importance of 1, 2, 3, 4, 5, Callogorgia verticillata, Acanthogorgia spp., Placogorgia these geological features as hotspots and shelters/refuges species and habitats that are threatened, in Gorgonian/coral gardens: 6, 7, 8, 9, 11, coronata, Swiftia pallida, Muriceides lepida, Villogorgia regression, or rare in other Mediterranean areas. 12, 13, 14 bebrycoides, Bebryce mollis, Nicella granifera 1, 4, 5, 6, 7, Leiopathes glaberrima, Antipathes dichotoma, Antipathella METHODOLOGY Black corals Since 2006, Oceana has carried out six expeditions in the Mediterranean performing 129 ROV’s dives 9, 11, 15, 16 subpinnata, Parantipathes larix Isidella elongata, Pennatula spp., Pteroeides griseum, 2, 3, 4, 7, 8, over 16 seamounts, between ‑37 and ‑638 meters deep. Soft bottoms’ octocorals Virgularia mirabilis, Veretillun cynomorium, Kophobelemnon 9, 11, 14, 16 RESULTS stelliferum, Funiculina quadrangularis 2 3, 4, 5, 6, 7, Asconema setubalense, Phakellia spp., Axinella spp. -
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). -
Active Continental Margin
Encyclopedia of Marine Geosciences DOI 10.1007/978-94-007-6644-0_102-2 # Springer Science+Business Media Dordrecht 2014 Active Continental Margin Serge Lallemand* Géosciences Montpellier, University of Montpellier, Montpellier, France Synonyms Convergent boundary; Convergent margin; Destructive margin; Ocean-continent subduction; Oceanic subduction zone; Subduction zone Definition An active continental margin refers to the submerged edge of a continent overriding an oceanic lithosphere at a convergent plate boundary by opposition with a passive continental margin which is the remaining scar at the edge of a continent following continental break-up. The term “active” stresses the importance of the tectonic activity (seismicity, volcanism, mountain building) associated with plate convergence along that boundary. Today, people typically refer to a “subduction zone” rather than an “active margin.” Generalities Active continental margins, i.e., when an oceanic plate subducts beneath a continent, represent about two-thirds of the modern convergent margins. Their cumulated length has been estimated to 45,000 km (Lallemand et al., 2005). Most of them are located in the circum-Pacific (Japan, Kurils, Aleutians, and North, Middle, and South America), Southeast Asia (Ryukyus, Philippines, New Guinea), Indian Ocean (Java, Sumatra, Andaman, Makran), Mediterranean region (Aegea, Cala- bria), or Antilles. They are generally “active” over tens (Tonga, Mariana) or hundreds (Japan, South America) of millions of years. This longevity has consequences on their internal structure, especially in terms of continental growth by tectonic accretion of oceanic terranes, or by arc magmatism, but also sometimes in terms of continental consumption by tectonic erosion. Morphology A continental margin generally extends from the coast down to the abyssal plain (see Fig. -
Microbiology of Seamounts Is Still in Its Infancy
or collective redistirbution of any portion of this article by photocopy machine, reposting, or other means is permitted only with the approval of The approval portionthe ofwith any articlepermitted only photocopy by is of machine, reposting, this means or collective or other redistirbution This article has This been published in MOUNTAINS IN THE SEA Oceanography MICROBIOLOGY journal of The 23, Number 1, a quarterly , Volume OF SEAMOUNTS Common Patterns Observed in Community Structure O ceanography ceanography S BY DAVID EmERSON AND CRAIG L. MOYER ociety. © 2010 by The 2010 by O ceanography ceanography O ceanography ceanography ABSTRACT. Much interest has been generated by the discoveries of biodiversity InTRODUCTION S ociety. ociety. associated with seamounts. The volcanically active portion of these undersea Microbial life is remarkable for its resil- A mountains hosts a remarkably diverse range of unusual microbial habitats, from ience to extremes of temperature, pH, article for use and research. this copy in teaching to granted ll rights reserved. is Permission S ociety. ociety. black smokers rich in sulfur to cooler, diffuse, iron-rich hydrothermal vents. As and pressure, as well its ability to persist S such, seamounts potentially represent hotspots of microbial diversity, yet our and thrive using an amazing number or Th e [email protected] to: correspondence all end understanding of the microbiology of seamounts is still in its infancy. Here, we of organic or inorganic food sources. discuss recent work on the detection of seamount microbial communities and the Nowhere are these traits more evident observation that specific community groups may be indicative of specific geochemical than in the deep ocean. -
The Contribution of Wind-Generated Waves to Coastal Sea-Level Changes
1 Surveys in Geophysics Archimer November 2011, Volume 40, Issue 6, Pages 1563-1601 https://doi.org/10.1007/s10712-019-09557-5 https://archimer.ifremer.fr https://archimer.ifremer.fr/doc/00509/62046/ The Contribution of Wind-Generated Waves to Coastal Sea-Level Changes Dodet Guillaume 1, *, Melet Angélique 2, Ardhuin Fabrice 6, Bertin Xavier 3, Idier Déborah 4, Almar Rafael 5 1 UMR 6253 LOPSCNRS-Ifremer-IRD-Univiversity of Brest BrestPlouzané, France 2 Mercator OceanRamonville Saint Agne, France 3 UMR 7266 LIENSs, CNRS - La Rochelle UniversityLa Rochelle, France 4 BRGMOrléans Cédex, France 5 UMR 5566 LEGOSToulouse Cédex 9, France *Corresponding author : Guillaume Dodet, email address : [email protected] Abstract : Surface gravity waves generated by winds are ubiquitous on our oceans and play a primordial role in the dynamics of the ocean–land–atmosphere interfaces. In particular, wind-generated waves cause fluctuations of the sea level at the coast over timescales from a few seconds (individual wave runup) to a few hours (wave-induced setup). These wave-induced processes are of major importance for coastal management as they add up to tides and atmospheric surges during storm events and enhance coastal flooding and erosion. Changes in the atmospheric circulation associated with natural climate cycles or caused by increasing greenhouse gas emissions affect the wave conditions worldwide, which may drive significant changes in the wave-induced coastal hydrodynamics. Since sea-level rise represents a major challenge for sustainable coastal management, particularly in low-lying coastal areas and/or along densely urbanized coastlines, understanding the contribution of wind-generated waves to the long-term budget of coastal sea-level changes is therefore of major importance. -
Upwelling As a Source of Nutrients for the Great Barrier Reef Ecosystems: a Solution to Darwin's Question?
Vol. 8: 257-269, 1982 MARINE ECOLOGY - PROGRESS SERIES Published May 28 Mar. Ecol. Prog. Ser. / I Upwelling as a Source of Nutrients for the Great Barrier Reef Ecosystems: A Solution to Darwin's Question? John C. Andrews and Patrick Gentien Australian Institute of Marine Science, Townsville 4810, Queensland, Australia ABSTRACT: The Great Barrier Reef shelf ecosystem is examined for nutrient enrichment from within the seasonal thermocline of the adjacent Coral Sea using moored current and temperature recorders and chemical data from a year of hydrology cruises at 3 to 5 wk intervals. The East Australian Current is found to pulsate in strength over the continental slope with a period near 90 d and to pump cold, saline, nutrient rich water up the slope to the shelf break. The nutrients are then pumped inshore in a bottom Ekman layer forced by periodic reversals in the longshore wind component. The period of this cycle is 12 to 25 d in summer (30 d year round average) and the bottom surges have an alternating onshore- offshore speed up to 10 cm S-'. Upwelling intrusions tend to be confined near the bottom and phytoplankton development quickly takes place inshore of the shelf break. There are return surface flows which preserve the mass budget and carry silicate rich Lagoon water offshore while nitrogen rich shelf break water is carried onshore. Upwelling intrusions penetrate across the entire zone of reefs, but rarely into the Lagoon. Nutrition is del~veredout of the shelf thermocline to the living coral of reefs by localised upwelling induced by the reefs. -
Oceans in Motion TCS 2018
TCS Marine Biology C. Woodward Oceans in Motion TCS 2018 Oceans in Motion Oceans in Motion – TIDES (“la marea”) • Caused by gravitational forces between moon & Earth • Also influenced by sun, tilt of Earth, topography, and other factors DAILY TIDE CYCLE • 2 high tides, 2 low tides per 24 hrs (due to Earth’s rotation) • Tides get ~1 hr later each day gravitational pull of moon See Figs. Oceans in Motion - TIDES MONTHLY TIDE CYCLE • Due to moon’s orbit around Earth, and gravitational pull of moon & sun • 2 spring and 2 neap tides per month Fig. 3.33 Catherine Woodward 1 of 6 Tropical Conservation Semester 1 TCS Marine Biology C. Woodward Oceans in Motion TCS 2018 Oceans in Motion – WAVES (“las olas”) SURFACE WATER MOVEMENT is wind driven Waves = upper surface; move water only to ≈1/2 wavelength (λ) Nybakken Fig 1.10 See C&H Fig. 3.27 Oceans in Motion Water movement is circular But circles not closed, especially in big waves and shallow water. Stoke’s Drift = displacement of water in the direction of wave movement Oceans in Motion SWELLS Wave size determined by: • Wind speed • Fetch • Duration See C&H Fig. 3.29 Longer waves move faster Catherine Woodward 2 of 6 Tropical Conservation Semester 2 TCS Marine Biology C. Woodward Oceans in Motion TCS 2018 Oceans in Motion – CURRENTS (“la corriente”) NEAR-SHORE CURRENTS • Created by wind (= waves) and shore topography • Longshore current, undertow, rip current Undertow: The seaward return of water along the bottom underneath breaking waves Oceans in Motion NEAR-SHORE CURRENTS • Created by wind (= waves) and shore topography • Longshore current, undertow, rip current Longshore current: Results when waves hit shore at an angle, pushing water and material down the shore.