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  • 1
    Monograph available for loan
    Monograph available for loan
    Cambridge : Cambridge Univ. Press
    Call number: 13/M 99.0115 ; PIK N453-00-0549 ; AWI S1-98-0188
    Description / Table of Contents: The movement of oceanic water has important consequences for a variety of applications, such as climate change, sealevel change, biological productivity, weather forecasting, and many others. This book addresses the problem of inferring the state of the ocean circulation, understanding it dynamically, and even forecasting it through a quantitative combination of theory and observation. It focuses on so-called inverse methods and related methods of statistical inference. Both time-independent and time-dependent problems are considered, including Gauss-Markov estimation, sequential estimators, and adjoint / Pontryagin principle methods. This book is intended for use as a graduate-level text for students of oceanography and other related fields. It will also be of interest to working physical ocanographers.
    Type of Medium: Monograph available for loan
    Pages: xiv, 442 S. , graph. Darst., Kt.
    Edition: 1. publ.
    ISBN: 0521480906
    Classification: D.3.
    Language: English
    Note: Contents: Preface. - Notation. - 1 Introduction. - 1.1 Background. - 1.2 What is an inverse problem?. - 1.3 What's here. - 2 Physics of the ocean circulation. - 2.1 Basic physical elements. - 2.2 Observations. - 2.3 The classical problem. - 2.4 Hidaka's problem and the algebraic formulation. - 2.5 The absolute velocity problem in retrospect. - 3 Basic machinery. - 3.1 Matrix and vector algebra. - 3.2 Simple statistics; regression. - 3.3 Least squares. - 3.4 The singular vector expansion. - 3.5 Using a steady model-combined least squares and adjoints. - 3.6 Gauss-Markov estimation, mapmaking, and more simultaneous equations. - 3.7 Improving solutions recursively. - 3.8 Estimation from linear constraints - a summary. - 4 The steady ocean circulation inverse problem. - 4.1 Choosing a model. - 4.2 The initial reference level. - 4.3 Simple examples. - 4.4 Property fluxes. - 4.5 Application to real data sets. - 4.6 Climatologies and box models. - 4.7 The β-spiral and variant methods. - 5 Additional useful methods. - 5.1 Inequality constraints; nonnegative least squares. - 5.2 Linear programming and eclectic models. - 5.3 Quantifying water mass; empirical orthogonal functions. - 5.4 Kriging and other variants of Gauss-Markov estimation. - 5.5 Nonlinear problems. - 6 The time-dependent inverse problem. - 6.1 Some basic ideas and notation. - 6.2 Estimation. - 6.3 Control problems: Pontryagin principle and adjoint methods. - 6.4 Duality and simplification: steady-state filter and adjoint. - 6.5 Controllability and observability. - 6.6 Nonlinear models. - 6.7 Assimilation. - 6.8 Other minimization methods and the search for practicality. - 6.9 Forward models. - 6.10 A last word. - References. - Author Index. - Subject Index.
    Location: Reading room
    Location: Reading room
    Location: Reading room
    Branch Library: GFZ Library
    Branch Library: PIK Library
    Branch Library: AWI Library
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  • 2
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 307 (1984), S. 447-450 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] To make a direct comparison of temperature in the two investigations, we have interpolated the data to common locations (excluding segments at the ends where the lines did not coincide). A fine mesh was generated (grid points over 40m vertically and every 10 km horizontally) using the technique of ...
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 301 (1983), S. 408-410 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Flg. l The sea surface topography (cm) of the Pacific Ocean relative to the geoid as determined solely from satellite measurements. It is viewed through a low pass wavenumber filter. The arrows denote the direction of the geostrophic surface velocity which corresponds to this elevation. The sea ...
    Type of Medium: Electronic Resource
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  • 4
    Publication Date: 2014-04-02
    Description: Over the last decade, several hundred seals have been equipped with conductivity-temperature-depth sensors in the Southern Ocean for both biological and physical oceanographic studies. A calibrated collection of seal-derived hydrographic data is now available, consisting of more than 165,000 profiles. The value of these hydrographic data within the existing Southern Ocean observing system is demonstrated herein by conducting two state estimation experiments, differing only in the use or not of seal data to constrain the system. Including seal-derived data substantially modifies the estimated surface mixedlayer properties and circulation patterns within and south of the Antarctic Circumpolar Current. Agreement with independent satellite observations of sea ice concentration is improved, especially along the East Antarctic shelf. Instrumented animals efficiently reduce a critical observational gap, and their contribution to monitoring polar climate variability will continue to grow as data accuracy and spatial coverage increase.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
    Format: application/pdf
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  • 5
    Publication Date: 2017-01-04
    Description: Author Posting. © American Geophysical Union, 2004. 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 109 (2004): C01007, doi:10.1029/2003JC002014.
    Description: Adjoint sensitivities of CFC-11 concentrations and CFC-11/CFC-12 ratio ages in a North Atlantic general circulation model are analyzed. These sensitivities are compared with those of spiciness, T − (β/α) S, where α, β are the thermal and haline expansion coefficients, respectively. High-sensitivity fields are candidates for providing the most powerful constraints in the corresponding inverse problems. In the dual (adjoint) solutions all three variables exhibit the major ventilation pathways and define the associated timescales in the model. Overall, however, spiciness shows the highest sensitivity to the flow field. In the North Atlantic Deep Water, sensitivities of CFC properties and spiciness to the isopycnal mixing and thickness diffusion are of the same order of magnitude. In the lower subtropical thermocline, sensitivities of CFC properties to the isopycnal mixing and thickness diffusion are higher. The utility of this sensitivity is undermined by the need to reconstruct their boundary conditions. Given the influence of T, S measurements on the density field, they produce the most powerful constraints on the model on the large scale. It still remains possible, however, that transient tracers can provide a larger relative information content concerning the mixing process between the near-surface boundary layer and the thermocline but dependent upon the ability to reconstruct accurate initial and boundary conditions.
    Description: This work was supported by NSF Award OCE-9730071, OCE-9617570, NASA Award NAG5-7857 and NAG5- 11933.
    Keywords: Transient tracers ; State estimation ; Adjoint sensitivity
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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  • 6
    Publication Date: 2017-01-04
    Description: Author Posting. © The Author(s), 2012. This is the author's version of the work. It is posted here by permission of National Academy of Sciences for personal use, not for redistribution. The definitive version was published in Proceedings of the National Academy of Sciences of the United States of America 110 (2013): 4435-4436, doi:10.1073/pnas.1302536110.
    Description: Predicting climate change is a high priority for society, but such forecasts are notoriously uncertain. Why? Even should climate prove theoretically predictable---by no means certain---the near-absence of adequate observations will preclude its understanding and hence even the hope of useful predictions. Geological and cryospheric records of climate change and our brief recent record of instrumental observations show that the climate system is changeable on all time scales---from a few years out to the age of the earth. Major physical, chemical, and biological processes influence the climate system on decades, centuries, and millennia. Glaciers fluctuate on time scales of years to centuries and beyond. Since the Industrial Revolution, carbon dioxide has been emitted through fossil fuel burning, and it will be absorbed, recycled, and transferred amongst the atmosphere, ocean, and biosphere over decades to thousands of years.
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
    Format: application/pdf
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  • 7
    Publication Date: 2016-05-12
    Description: Author Posting. © American Geophysical Union, 2015. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography 30 (2015): 1470-1489, doi:10.1002/2014PA002743.
    Description: The ocean circulation modifies mixed layer (ML) tracer signals as they are communicated to the deep ocean by advection and mixing. We develop and apply a procedure for using tracer signals observed “upstream” (by planktonic foraminifera) and “downstream” (by benthic foraminifera) to constrain how tracer signals are modified by the intervening circulation and, by extension, to constrain properties of that circulation. A history of ML equilibrium calcite δ18O (δ18Oc) spanning the last deglaciation is inferred from a least-squares fit of eight benthic foraminiferal δ18Oc records to Green's function estimated for the modern ocean circulation. Disagreements between this history and the ML history implied by planktonic records would indicate deviations from the modern circulation. No deviations are diagnosed because the two estimates of ML δ18Oc agree within their uncertainties, but we suggest data collection and modeling procedures useful for inferring circulation changes in future studies. Uncertainties of benthic-derived ML δ18Oc are lowest in the high-latitude regions chiefly responsible for ventilating the deep ocean; additional high-resolution planktonic records constraining these regions are of particular utility. Benthic records from the Southern Ocean, where data are sparse, appear to have the most power to reduce uncertainties in benthic-derived ML δ18Oc. Understanding the spatiotemporal covariance of deglacial ML δ18Oc will also improve abilities of δ18Oc records to constrain deglacial circulation.
    Description: 2016-05-12
    Keywords: Oxygen isotopes ; Inverse modeling ; Deglaciation ; Tracers ; Ocean circulation ; Green's function
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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  • 8
    Publication Date: 2018-04-27
    Description: Author Posting. © American Geophysical Union, 2017. 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 122 (2017): 8208–8224, doi:10.1002/2017JC012985.
    Description: Estimates of the global ocean vertical velocities (Eulerian, eddy-induced, and residual) from a dynamically consistent and data-constrained ocean state estimate are presented and analyzed. Conventional patterns of vertical velocity, Ekman pumping, appear in the upper ocean, with topographic dominance at depth. Intense and vertically coherent upwelling and downwelling occur in the Southern Ocean, which are likely due to the interaction of the Antarctic Circumpolar Current and large-scale topographic features and are generally canceled out in the conventional zonally averaged results. These “elevators” at high latitudes connect the upper to the deep and abyssal oceans and working together with isopycnal mixing are likely a mechanism, in addition to the formation of deep and abyssal waters, for fast responses of the deep and abyssal oceans to the changing climate. Also, Eulerian and parameterized eddy-induced components are of opposite signs in numerous regions around the global ocean, particularly in the ocean interior away from surface and bottom. Nevertheless, residual vertical velocity is primarily determined by the Eulerian component, and related to winds and large-scale topographic features. The current estimates of vertical velocities can serve as a useful reference for investigating the vertical exchange of ocean properties and tracers, and its complex spatial structure ultimately permits regional tests of basic oceanographic concepts such as Sverdrup balance and coastal upwelling/downwelling.
    Description: National Science Foundation Grant Numbers: OCE-1736633 , OCE-1534618 , OCE-0961713; National Oceanic and Atmospheric Administration Grant Number: NA10OAR4310135
    Description: 2018-04-27
    Keywords: Vertical velocity ; Vertical transport ; Vertical exchange ; Ocean state estimate ; Climate change ; Southern Ocean
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 9
    Publication Date: 2017-01-04
    Description: Author Posting. © American Geophysical Union, 2006. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography 21 (2006): PA4206, doi:10.1029/2005PA001241.
    Description: The consequences of the hypothesis that Milankovitch forcing affects the phase (e.g., termination times) of the 100 kyr glacial cycles via a mechanism known as “nonlinear phase locking” are examined. Phase locking provides a mechanism by which Milankovitch forcing can act as the “pacemaker” of the glacial cycles. Nonlinear phase locking can determine the timing of the major deglaciations, nearly independently of the specific mechanism or model that is responsible for these cycles as long as this mechanism is suitably nonlinear. A consequence of this is that the fit of a certain model output to the observed ice volume record cannot be used as an indication that the glacial mechanism in this model is necessarily correct. Phase locking to obliquity and possibly precession variations is distinct from mechanisms relying on a linear or nonlinear amplification of the eccentricity forcing. Nonlinear phase locking may determine the phase of the glacial cycles even in the presence of noise in the climate system and can be effective at setting glacial termination times even when the precession and obliquity bands account only for a small portion of the total power of an ice volume record. Nonlinear phase locking can also result in the observed “quantization” of the glacial period into multiples of the obliquity or precession periods.
    Description: E.T. is funded by NSF Paleoclimate program, grant ATM-0455470 and by the McDonnell Foundation. P.H. is supported by the NOAA Postdoctoral Program in Climate and Global Change. C.W. is supported by the National Ocean Partnership Program (NOPP). M.E.R. is supported by NSF grant ATM-0455328.
    Keywords: Glacial cycles ; Phase locking ; Milankovitch
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 10
    Publication Date: 2018-09-17
    Description: Author Posting. © American Meteorological Society, 2018. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Climate 31 (2018): 8059-8079, doi:10.1175/JCLI-D-17-0769.1.
    Description: We use the method of least squares with Lagrange multipliers to fit an ocean general circulation model to the Multiproxy Approach for the Reconstruction of the Glacial Ocean Surface (MARGO) estimate of near sea surface temperature (NSST) at the Last Glacial Maximum (LGM; circa 23–19 thousand years ago). Compared to a modern simulation, the resulting global, last-glacial ocean state estimate, which fits the MARGO data within uncertainties in a free-running coupled ocean–sea ice simulation, has global-mean NSSTs that are 2°C lower and greater sea ice extent in all seasons in both the Northern and Southern Hemispheres. Increased brine rejection by sea ice formation in the Southern Ocean contributes to a stronger abyssal stratification set principally by salinity, qualitatively consistent with pore fluid measurements. The upper cell of the glacial Atlantic overturning circulation is deeper and stronger. Dye release experiments show similar distributions of Southern Ocean source waters in the glacial and modern western Atlantic, suggesting that LGM NSST data do not require a major reorganization of abyssal water masses. Outstanding challenges in reconstructing LGM ocean conditions include reducing effects from model biases and finding computationally efficient ways to incorporate abyssal tracers in global circulation inversions. Progress will be aided by the development of coupled ocean–atmosphere–ice inverse models, by improving high-latitude model processes that connect the upper and abyssal oceans, and by the collection of additional paleoclimate observations.
    Description: DEA was supported by a NSF Graduate Research Fellowship and NSF Grant OCE-1060735. OM acknowledges support from the NSF. GF was supported by NASA Award 1553749 and Simons Foundation Award 549931.
    Keywords: Ocean ; Abyssal circulation ; Sea surface temperature ; Paleoclimate ; Inverse methods ; Ocean models
    Repository Name: Woods Hole Open Access Server
    Type: Article
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