Cross-Equatorial Flow Through an Abyssal Channel Under The
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2. an Approach to Antarctic Glacial History: the Aims of Leg 1781
Barker, P.F., Camerlenghi, A., Acton, G.D., et al., 1999 Proceedings of the Ocean Drilling Program, Initial Reports Volume 178 2. AN APPROACH TO ANTARCTIC GLACIAL HISTORY: THE AIMS OF LEG 1781 P.F. Barker2 and A. Camerlenghi3 Ocean Drilling Program (ODP) Leg 178 was proposed partly as an examination of Antarctic Peninsula glacial history and partly as a test of the strategy of determining this history by sampling glacially trans- ported sediments at the continental margin. If successful, it could lead to a program of two or three other legs around Antarctica that, in com- bination, might determine the long-term history of the entire Antarctic Ice Sheet. Leg 178 also had a second objective: to obtain a long, high- resolution record of Holocene climate from Palmer Deep, an isolated deep basin on the inner continental shelf. The proposal that became Leg 178 was therefore based on several assumptions, described below. Briefly, they are: 1. The Antarctic Ice Sheet is now and has been throughout its ex- istence an important component of the Earth’s climate engine, which it is necessary to document and understand. 2. An understanding of the ice sheet’s function and what controls its development cannot be obtained until its history is known. 3. Existing knowledge of Antarctic glacial history, derived largely from sparse onshore data and low-latitude climate proxies, is in- adequate and ambiguous; the proxies themselves disagree. Fur- thermore, continued use of the same proxies and onshore data is unlikely to resolve present ambiguities and disputes. 1Examples of how to reference the 4. -
Relationship Between Continental Rise Development and Palaeo-Ice Sheet Dynamics, Northern Antarctic Peninsula Pacific Margin
ARTICLE IN PRESS Quaternary Science Reviews 25 (2006) 933–944 Relationship between continental rise development and palaeo-ice sheet dynamics, Northern Antarctic Peninsula Pacific margin David Amblasa, Roger Urgelesa, Miquel Canalsa,Ã, Antoni M. Calafata, Michele Rebescob, Angelo Camerlenghia, Ferran Estradac, Marc De Batistd, John E. Hughes-Clarkee aGRC Geocie`ncies Marines, Universitat de Barcelona, Martı´ i Franque`s s/n, E-08028 Barcelona, Spain bIstituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS), Borgo Grotta Gigante 42/c, 34010 Sgonico, Trieste, Italy cCSIC Institut de Cie`ncies del Mar, Passeig Marı´tim Barceloneta 37-49, 08003 Barcelona, Spain dRenard Centre of Marine Geology, Ghent University, Krijgslaan 281 S8, B-9000 Gent, Belgium eOcean Mapping Group, University of New Brunswick, Fredericton, New Brunswick, Canada E3B 5A3 Received 17 December 2004; accepted 10 July 2005 Abstract Acquisition of swath bathymetry data west of the North Antarctic Peninsula (NAP), between 631S and 661S, and its integration with the predicted seafloor topography of Smith and Sandwell [Global seafloor topography from satellite altimetry and ship depth soundings. Science 277, 1956–1962.] reveal the links between the continental rise depositional systems and the NAP palaeo-ice sheet dynamics. The NAP Pacific margin consists of a wide continental shelf dissected by several troughs, tens of kilometres wide and long. The Biscoe Trough, which has been almost entirely surveyed with multibeam sonar, shows spectacular fan-shaped streamlining sea-floor morphologies revealing the presence of ice streams during the Last Glacial Maximum. In the study area the continental rise comprises the six northernmost sediment mounds of the NAP Pacific margin and the canyon-channel systems between them. -
Glacial Ocean Circulation and Stratification Explained by Reduced
Glacial ocean circulation and stratification explained by reduced atmospheric temperature Malte F. Jansena,1 aDepartment of the Geophysical Sciences, The University of Chicago, Chicago, IL 60637 Edited by Mark H. Thiemens, University of California, San Diego, La Jolla, CA, and approved November 7, 2016 (received for review June 27, 2016) Earth’s climate has undergone dramatic shifts between glacial and We test the connection between atmospheric temperature interglacial time periods, with high-latitude temperature changes and ocean circulation and stratification changes, using idealized on the order of 5–10 ◦C. These climatic shifts have been asso- numerical simulations, which allow us to isolate the proposed ciated with major rearrangements in the deep ocean circulation mechanism. We use a coupled ocean–sea-ice model, with atmo- and stratification, which have likely played an important role in spheric temperature, winds, and evaporation–precipitation pre- the observed atmospheric carbon dioxide swings by affecting the scribed as boundary conditions (Materials and Methods). The partitioning of carbon between the atmosphere and the ocean. model uses an idealized continental configuration resembling the The mechanisms by which the deep ocean circulation changed, Atlantic and Southern Oceans, where the most elemental circu- however, are still unclear and represent a major challenge to our lation changes have been inferred (3, 5, 6, 12). understanding of glacial climates. This study shows that vari- ous inferred changes in the deep ocean circulation and stratifica- Results tion between glacial and interglacial climates can be interpreted We first focus on the model’s ability to reproduce key features as a direct consequence of atmospheric temperature differences. -
Coastal and Ocean Engineering
May 18, 2020 Coastal and Ocean Engineering John Fenton Institute of Hydraulic Engineering and Water Resources Management Vienna University of Technology, Karlsplatz 13/222, 1040 Vienna, Austria URL: http://johndfenton.com/ URL: mailto:[email protected] Abstract This course introduces maritime engineering, encompassing coastal and ocean engineering. It con- centrates on providing an understanding of the many processes at work when the tides, storms and waves interact with the natural and human environments. The course will be a mixture of descrip- tion and theory – it is hoped that by understanding the theory that the practicewillbemadeallthe easier. There is nothing quite so practical as a good theory. Table of Contents References ....................... 2 1. Introduction ..................... 6 1.1 Physical properties of seawater ............. 6 2. Introduction to Oceanography ............... 7 2.1 Ocean currents .................. 7 2.2 El Niño, La Niña, and the Southern Oscillation ........10 2.3 Indian Ocean Dipole ................12 2.4 Continental shelf flow ................13 3. Tides .......................15 3.1 Introduction ...................15 3.2 Tide generating forces and equilibrium theory ........15 3.3 Dynamic model of tides ...............17 3.4 Harmonic analysis and prediction of tides ..........19 4. Surface gravity waves ..................21 4.1 The equations of fluid mechanics ............21 4.2 Boundary conditions ................28 4.3 The general problem of wave motion ...........29 4.4 Linear wave theory .................30 4.5 Shoaling, refraction and breaking ............44 4.6 Diffraction ...................50 4.7 Nonlinear wave theories ...............51 1 Coastal and Ocean Engineering John Fenton 5. The calculation of forces on ocean structures ...........54 5.1 Structural element much smaller than wavelength – drag and inertia forces .....................54 5.2 Structural element comparable with wavelength – diffraction forces ..56 6. -
Antarctic Sea Ice Control on Ocean Circulation in Present and Glacial Climates
Antarctic sea ice control on ocean circulation in present and glacial climates Raffaele Ferraria,1, Malte F. Jansenb, Jess F. Adkinsc, Andrea Burkec, Andrew L. Stewartc, and Andrew F. Thompsonc aDepartment of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139; bAtmospheric and Oceanic Sciences Program, Geophysical Fluid Dynamics Laboratory, Princeton, NJ 08544; and cDivision of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125 Edited* by Edward A. Boyle, Massachusetts Institute of Technology, Cambridge, MA, and approved April 16, 2014 (received for review December 31, 2013) In the modern climate, the ocean below 2 km is mainly filled by waters possibly associated with an equatorward shift of the Southern sinking into the abyss around Antarctica and in the North Atlantic. Hemisphere westerlies (11–13), (ii) an increase in abyssal stratifi- Paleoproxies indicate that waters of North Atlantic origin were instead cation acting as a lid to deep carbon (14), (iii)anexpansionofseaice absent below 2 km at the Last Glacial Maximum, resulting in an that reduced the CO2 outgassing over the Southern Ocean (15), and expansion of the volume occupied by Antarctic origin waters. In this (iv) a reduction in the mixing between waters of Antarctic and Arctic study we show that this rearrangement of deep water masses is origin, which is a major leak of abyssal carbon in the modern climate dynamically linked to the expansion of summer sea ice around (16). Current understanding is that some combination of all of these Antarctica. A simple theory further suggests that these deep waters feedbacks, together with a reorganization of the biological and only came to the surface under sea ice, which insulated them from carbonate pumps, is required to explain the observed glacial drop in atmospheric forcing, and were weakly mixed with overlying waters, atmospheric CO2 (17). -
Chapter 7 Arctic Oceanography; the Path of North Atlantic Deep Water
Chapter 7 Arctic oceanography; the path of North Atlantic Deep Water The importance of the Southern Ocean for the formation of the water masses of the world ocean poses the question whether similar conditions are found in the Arctic. We therefore postpone the discussion of the temperate and tropical oceans again and have a look at the oceanography of the Arctic Seas. It does not take much to realize that the impact of the Arctic region on the circulation and water masses of the World Ocean differs substantially from that of the Southern Ocean. The major reason is found in the topography. The Arctic Seas belong to a class of ocean basins known as mediterranean seas (Dietrich et al., 1980). A mediterranean sea is defined as a part of the world ocean which has only limited communication with the major ocean basins (these being the Pacific, Atlantic, and Indian Oceans) and where the circulation is dominated by thermohaline forcing. What this means is that, in contrast to the dynamics of the major ocean basins where most currents are driven by the wind and modified by thermohaline effects, currents in mediterranean seas are driven by temperature and salinity differences (the salinity effect usually dominates) and modified by wind action. The reason for the dominance of thermohaline forcing is the topography: Mediterranean Seas are separated from the major ocean basins by sills, which limit the exchange of deeper waters. Fig. 7.1. Schematic illustration of the circulation in mediterranean seas; (a) with negative precipitation - evaporation balance, (b) with positive precipitation - evaporation balance. -
Tidal Modulation of Antarctic Ice Shelf Melting Ole Richter1,2, David E
Tidal Modulation of Antarctic Ice Shelf Melting Ole Richter1,2, David E. Gwyther1, Matt A. King2, and Benjamin K. Galton-Fenzi3 1Institute for Marine and Antarctic Studies, University of Tasmania, Private Bag 129, Hobart, TAS, 7001, Australia. 2Geography & Spatial Sciences, School of Technology, Environments and Design, University of Tasmania, Hobart, TAS, 7001, Australia. 3Australian Antarctic Division, Kingston, TAS, 7050, Australia. Correspondence: Ole Richter ([email protected]) This is a non-peer reviewed preprint submitted to EarthArXiv. This preprint has also been submitted to The Cryosphere for peer review. 1 Abstract. Tides influence basal melting of individual Antarctic ice shelves, but their net impact on Antarctic-wide ice-ocean interaction has yet to be constrained. Here we quantify the impact of tides on ice shelf melting and the continental shelf seas 5 by means of a 4 km resolution circum-Antarctic ocean model. Activating tides in the model increases the total basal mass loss by 57 Gt/yr (4 %), while decreasing continental shelf temperatures by 0.04 ◦C, indicating a slightly more efficient conversion of ocean heat into ice shelf melting. Regional variations can be larger, with melt rate modulations exceeding 500 % and temperatures changing by more than 0.5 ◦C, highlighting the importance of capturing tides for robust modelling of glacier systems and coastal oceans. Tide-induced changes around the Antarctic Peninsula have a dipolar distribution with decreased 10 ocean temperatures and reduced melting towards the Bellingshausen Sea and warming along the continental shelf break on the Weddell Sea side. This warming extends under the Ronne Ice Shelf, which also features one of the highest increases in area-averaged basal melting (150 %) when tides are included. -
This Manuscript Has Been Submitted for Publication in Scientific Reports
This manuscript has been submitted for publication in Scientific Reports. Please not that, despite having undergone peer-review, the manuscript has yet to be formally accepted for publication. Subsequent versions of the manuscript may have slightly different content. If accepted, the final version of this manuscript will be available via the “Peer-reviewed Publication DOI” link on the EarthArXiv webpage. Please feel free to contact any of the authors; we welcome feedback. 1 Ventilation of the abyss in the Atlantic sector of the 2 Southern Ocean 1,* 1 2,3 3 Camille Hayatte Akhoudas , Jean-Baptiste Sallee´ , F. Alexander Haumann , Michael P. 3 4 1 4 5 4 Meredith , Alberto Naveira Garabato , Gilles Reverdin , Lo¨ıcJullion , Giovanni Aloisi , 6 7,8 7 5 Marion Benetti , Melanie J. Leng , and Carol Arrowsmith 1 6 Sorbonne Universite,´ CNRS/IRD/MNHN, Laboratoire d’Oceanographie´ et du Climat - Experimentations´ et 7 Approches Numeriques,´ Paris, France 2 8 Atmospheric and Oceanic Sciences Program, Princeton University, Princeton, United States 3 9 British Antarctic Survey, Cambridge, United Kingdom 4 10 School of Ocean and Earth Science, National Oceanography Centre, University of Southampton, United 11 Kingdom 5 12 Institut de Physique du Globe de Paris, Sorbonne Paris Cite,´ Universite´ Paris Diderot, UMR 7154 CNRS, Paris, 13 France 6 14 Institute of Earth Sciences, University of Iceland, Reykjavik, Iceland 7 15 NERC Isotope Geosciences Laboratory, British Geological Survey, Nottingham, United Kingdom 8 16 Centre for Environmental Geochemistry, University of Nottingham, United Kingdom * 17 [email protected] 18 ABSTRACT The Atlantic sector of the Southern Ocean is the world’s main production site of Antarctic Bottom Water, a water-mass that is ventilated at the ocean surface before sinking and entraining older water-masses – ultimately replenishing the abyssal global ocean. -
Effects of Drake Passage on a Strongly Eddying Global Ocean
PALEOCEANOGRAPHY, VOL. ???, XXXX, DOI:10.1029/, Effects of Drake Passage on a strongly eddying global ocean Jan P. Viebahn,1 Anna S. von der Heydt,1 Dewi Le Bars,1 and Henk A. Dijkstra1 1Institute for Marine and Atmospheric Research Utrecht, Utrecht University, Utrecht, Netherlands. arXiv:1510.04141v1 [physics.ao-ph] 14 Oct 2015 D R A F T October 15, 2018, 2:47pm D R A F T X - 2 VIEBAHN ET AL.: DRAKE PASSAGE IN AN EDDYING GLOBAL OCEAN The climate impact of ocean gateway openings during the Eocene-Oligocene transition is still under debate. Previous model studies employed grid res- olutions at which the impact of mesoscale eddies has to be parameterized. We present results of a state-of-the-art eddy-resolving global ocean model with a closed Drake Passage, and compare with results of the same model at non-eddying resolution. An analysis of the pathways of heat by decom- posing the meridional heat transport into eddy, horizontal, and overturning circulation components indicates that the model behavior on the large scale is qualitatively similar at both resolutions. Closing Drake Passage induces (i) sea surface warming around Antarctica due to changes in the horizon- tal circulation of the Southern Ocean, (ii) the collapse of the overturning cir- culation related to North Atlantic Deep Water formation leading to surface cooling in the North Atlantic, (iii) significant equatorward eddy heat trans- port near Antarctica. However, quantitative details significantly depend on the chosen resolution. The warming around Antarctica is substantially larger for the non-eddying configuration (∼5:5◦C) than for the eddying configura- tion (∼2:5◦C). -
On the Circulation and Water Masses Over the Antarctic Continental Slope and Rise Between 80 and 1503E Nathaniel L
Deep-Sea Research II 47 (2000) 2299}2326 On the circulation and water masses over the Antarctic continental slope and rise between 80 and 1503E Nathaniel L. Bindo!! *, Mark A. Rosenberg!, Mark J. Warner" !Antarctic Co-operative Research Centre, GPO Box 252-80, Hobart, Tasmania 7001, Australia "School of Oceanography, University of Washington, Seattle, USA Received 18 December 1998; received in revised form 18 October 1999; accepted 22 December 1999 Abstract The circulation and water masses in the region between 80 and 1503E and from the Antarctic continental shelf to the Southern Boundary of the Antarctic Circumpolar Current (ACC) (&623S) are described from hydrographic and surface drifter data taken as part of the multi-disciplinary experiment, Baseline Research on Oceanography Krill and the Environment (BROKE). Two types of bottom water are identi"ed, Adelie Land Bottom Water, formed locally between 140 and 1503E, and Ross Sea Bottom Water. Ross Sea Bottom Water is found only at 1503E, whereas Adelie Land Bottom Water is found throughout the survey region. The bottom water mass properties become progressively warmer and saltier to the west, suggesting a westward #ow. All of the eight meridional CTD sections show an Antarctic Slope Front of varying strength and position with respect to the shelf break. In the water formation areas (between 140 and 1503E) and 1043E, the Antarctic Slope Front is more `Va shaped, while elsewhere it is one-sided. The shape of the slope front, and the presence or absence of water formation there, are consistent with other meridional sections in the Weddel Sea and simple theories of bottom-water formation (Gill, 1973. -
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. -
45. Sedimentary Facies and Depositional History of the Iberia Abyssal Plain1
Whitmarsh, R.B., Sawyer, D.S., Klaus, A., and Masson, D.G. (Eds.), 1996 Proceedings of the Ocean Drilling Program, Scientific Results, Vol. 149 45. SEDIMENTARY FACIES AND DEPOSITIONAL HISTORY OF THE IBERIA ABYSSAL PLAIN1 D. Milkert,2 B. Alonso,3 L. Liu,4 X. Zhao,5 M. Comas,6 and E. de Kaenel4 ABSTRACT During Leg 149, a transect of five sites (Sites 897 to 901) was cored across the rifted continental margin off the west coast of Portugal. Lithologic and seismostratigraphical studies, as well as paleomagnetic, calcareous nannofossil, foraminiferal, and dinocyst stratigraphic research, were completed. The depositional history of the Iberia Abyssal Plain is generally characterized by downslope transport of terrigenous sedi- ments, pelagic sedimentation, and contourite sediments. Sea-level changes and catastrophic events such as slope failure, trig- gered by earthquakes or oversteepening, are the main factors that have controlled the different sedimentary facies. We propose five stages for the evolution of the Iberia Abyssal Plain: (1) Upper Cretaceous and lower Tertiary gravitational flows, (2) Eocene pelagic sedimentation, (3) Oligocene and Miocene contourites, (4) a Miocene compressional phase, and (5) Pliocene and Pleistocene turbidite sedimentation. Major input of terrigenous turbidites on the Iberia Abyssal Plain began in the late Pliocene at 2.6 Ma. INTRODUCTION tured by both Mesozoic extension and Eocene compression (Pyrenean orogeny) (Boillot et al., 1979), and to a lesser extent by Miocene com- Leg 149 drilled a transect of sites (897 to 901) across the rifted mar- pression (Betic-Rif phase) (Mougenot et al., 1984). gin off Portugal over the ocean/continent transition in the Iberia Abys- Previous studies of the Cenozoic geology of the Iberian Margin sal Plain.