Hydrothermal Plumes
Hydrothermal Vent Fluids (Seafloor)
Layering of Oceanic Crust
Lithosphere: Structure and Composition
Mid-ocean Ridge Magmatism and Volcanism
Oceanic Rifts
Oceanic Spreading Centers
Peridotites
Plate Tectonics
Submarine Lava Types
MODELLING PAST OCEANS
Jürgen Sündermann
Institute of Oceanography (IFM), University of Hamburg,
Hamburg, Germany
Understanding the formation of the Earth’s surface and the
evolution of the Earth–Moon system requires knowledge
of the ocean’s circulation and tides through geological history. The most important tools to get this information are
numerical models simulating the physical and biogeochemical state of the sea. These models are widely tested
for the present Earth system. Research on climate, global
fluxes of matter, marine ecosystems, as well as operational
services like weather forecast are based on them. The
models are founded on the laws of nature (e.g., Newton’s
conservation of momentum) which are formulated as
mathematical equations and transformed into complex
program codes on major electronic computers. For model
validation, measured field data as sea-level elevations,
surface temperatures, or ice coverage are used. Past ocean
models were based on paleontological data of topography,
sediments, and marine organisms which were available for
times more than two billion years ago. The models are
driven by astronomical reconstructions of the Earth’s,
the Moon’s, and the Sun’s ancient orbital motions and
scenario-like assumptions on early volcanism, greenhouse
gases, sun spots, etc. Coupled ocean–atmosphere–
cryosphere–biosphere models simulating ancient circulations and climates, warm and cold periods, extend some
10–100 million years back (Heinemann et al., 2009). They
are most reliable for the Holocene with increasing accuracy toward the present (Fischer and Jungclaus, 2010).
Tidal models explaining geological sediment patterns or
the increases of the length of day and the Moon distance
cover the Earth’s history back to the Proterozoic (Kagan
and Sündermann, 1996). Examples are model calculations
of ocean currents and tides for the Gondwana period, for
the Tethys ocean, for the early Atlantic, for the world
ocean during last glacials and interglacials, and for the
recent millennium. From model results, we know today
that there exist multiple equilibrium states of the atmospheric and oceanic circulation, e.g., with and without
the Gulf stream. We also know that the rate of deceleration
of the Earth’s rotation by tidal friction through geological
history was not uniform due to continental drift and
changing ocean resonance.
Bibliography
Fischer, N., and Jungclaus, J. H., 2010. Effects of orbital forcing on
atmosphere and ocean heat transports in Holocene and Eemian
climate simulations with a comprehensive Earth system model.
Climate of the Past, 6, 155–168.
Heinemann, M., Jungclaus, J. H., and Marotzke, J., 2009. Warm
Paleocene/Eocene climate as simulated in ECHAM5/MPI-OM
source. Climate of the Past, 5, 785–802.
Kagan, B. A., and Sündermann, J., 1996. Dissipation of tidal
energy, paleotides and evolution of the Earth-Moon system.
Advances in Geophysics, 38, 179–266.
MODERN ANALOG TECHNIQUES
Michal Kucera
MARUM-Center for Marine Environmental Sciences,
University of Bremen, Bremen, Germany
Modern analog technique, often abbreviated as MAT, is a
popular type of transfer function used in paleoceanography to reconstruct past ocean properties from the
composition of fossil assemblages extracted from deepsea sediments. In the vast majority of cases, MAT is
applied to reconstruct past sea-surface temperature from
remains of marine unicellular microplankton such as
planktonic foraminifera, radiolaria, diatoms, and
dinoflagellates.
The method has been introduced to paleoceanography
by Hutson (1980). Mathematically, it is akin to k-nearest
neighbor regression. Its procedure is computationally
and conceptually very simple. First, a similarity coefficient is calculated between the composition of a fossil
assemblage in a geological sample and the compositions
of corresponding assemblages in a “calibration dataset”
of surface-sediment samples. Then, the surface-sediment
samples are sorted by their similarity coefficient, and a
subset of those with most similar assemblages, termed
the “nearest” or “best modern analogs,” is used in the second step to calculate an estimate of the desired ocean property. The estimate represents a mean of the present-day
values of the ocean property at the site of the deposition
of the best modern analogs, typically weighted by the
respective similarity coefficient of each sample. Like all
paleoceanographic transfer functions, MAT relies on the
assumption that the reconstructed ocean property is a statistically important determinant of the assemblage composition of the studied organisms. It also assumes that the
fossil assemblage and its covariance with the ocean property are represented in the calibration dataset. If this is not
the case, the fossil assemblage is said to represent a
no-analog condition, which may render the reconstruction
of past ocean properties invalid.
514
MODELLING PAST OCEANS
Hydrothermal Vent Fluids (Seafloor)
Layering of Oceanic Crust
Lithosphere: Structure and Composition
Mid-ocean Ridge Magmatism and Volcanism
Oceanic Rifts
Oceanic Spreading Centers
Peridotites
Plate Tectonics
Submarine Lava Types
MODELLING PAST OCEANS
Jürgen Sündermann
Institute of Oceanography (IFM), University of Hamburg,
Hamburg, Germany
Understanding the formation of the Earth’s surface and the
evolution of the Earth–Moon system requires knowledge
of the ocean’s circulation and tides through geological history. The most important tools to get this information are
numerical models simulating the physical and biogeochemical state of the sea. These models are widely tested
for the present Earth system. Research on climate, global
fluxes of matter, marine ecosystems, as well as operational
services like weather forecast are based on them. The
models are founded on the laws of nature (e.g., Newton’s
conservation of momentum) which are formulated as
mathematical equations and transformed into complex
program codes on major electronic computers. For model
validation, measured field data as sea-level elevations,
surface temperatures, or ice coverage are used. Past ocean
models were based on paleontological data of topography,
sediments, and marine organisms which were available for
times more than two billion years ago. The models are
driven by astronomical reconstructions of the Earth’s,
the Moon’s, and the Sun’s ancient orbital motions and
scenario-like assumptions on early volcanism, greenhouse
gases, sun spots, etc. Coupled ocean–atmosphere–
cryosphere–biosphere models simulating ancient circulations and climates, warm and cold periods, extend some
10–100 million years back (Heinemann et al., 2009). They
are most reliable for the Holocene with increasing accuracy toward the present (Fischer and Jungclaus, 2010).
Tidal models explaining geological sediment patterns or
the increases of the length of day and the Moon distance
cover the Earth’s history back to the Proterozoic (Kagan
and Sündermann, 1996). Examples are model calculations
of ocean currents and tides for the Gondwana period, for
the Tethys ocean, for the early Atlantic, for the world
ocean during last glacials and interglacials, and for the
recent millennium. From model results, we know today
that there exist multiple equilibrium states of the atmospheric and oceanic circulation, e.g., with and without
the Gulf stream. We also know that the rate of deceleration
of the Earth’s rotation by tidal friction through geological
history was not uniform due to continental drift and
changing ocean resonance.
Bibliography
Fischer, N., and Jungclaus, J. H., 2010. Effects of orbital forcing on
atmosphere and ocean heat transports in Holocene and Eemian
climate simulations with a comprehensive Earth system model.
Climate of the Past, 6, 155–168.
Heinemann, M., Jungclaus, J. H., and Marotzke, J., 2009. Warm
Paleocene/Eocene climate as simulated in ECHAM5/MPI-OM
source. Climate of the Past, 5, 785–802.
Kagan, B. A., and Sündermann, J., 1996. Dissipation of tidal
energy, paleotides and evolution of the Earth-Moon system.
Advances in Geophysics, 38, 179–266.
MODERN ANALOG TECHNIQUES
Michal Kucera
MARUM-Center for Marine Environmental Sciences,
University of Bremen, Bremen, Germany
Modern analog technique, often abbreviated as MAT, is a
popular type of transfer function used in paleoceanography to reconstruct past ocean properties from the
composition of fossil assemblages extracted from deepsea sediments. In the vast majority of cases, MAT is
applied to reconstruct past sea-surface temperature from
remains of marine unicellular microplankton such as
planktonic foraminifera, radiolaria, diatoms, and
dinoflagellates.
The method has been introduced to paleoceanography
by Hutson (1980). Mathematically, it is akin to k-nearest
neighbor regression. Its procedure is computationally
and conceptually very simple. First, a similarity coefficient is calculated between the composition of a fossil
assemblage in a geological sample and the compositions
of corresponding assemblages in a “calibration dataset”
of surface-sediment samples. Then, the surface-sediment
samples are sorted by their similarity coefficient, and a
subset of those with most similar assemblages, termed
the “nearest” or “best modern analogs,” is used in the second step to calculate an estimate of the desired ocean property. The estimate represents a mean of the present-day
values of the ocean property at the site of the deposition
of the best modern analogs, typically weighted by the
respective similarity coefficient of each sample. Like all
paleoceanographic transfer functions, MAT relies on the
assumption that the reconstructed ocean property is a statistically important determinant of the assemblage composition of the studied organisms. It also assumes that the
fossil assemblage and its covariance with the ocean property are represented in the calibration dataset. If this is not
the case, the fossil assemblage is said to represent a
no-analog condition, which may render the reconstruction
of past ocean properties invalid.
514
MODELLING PAST OCEANS