Deep Ocean Circulation and Benthic Environments

Efforts to understand deep gt 2500 m and mid-depth 1000-2500 m oceanic circulation over orbital time scales complements studies of surface oceanic conditions. Deep-ocean circulation changes over orbital time scales are important elements in orbital theory because the deep sea provides a way to translate regional insolation changes affecting high latitudes of the Northern Hemisphere into a global climate signal via the ocean's thermohaline circulation. Recall from chapter 2 that deep-water...

The Oceans

North Atlantic Deep Water Formations

The oceans are the world's largest reservoir of heat derived from solar insolation. Ocean circulation is the most important process transporting solar energy from low to high latitude areas and, through deep-oceanic circulation, around the world. Oceanic circulation is driven mainly by wind stress, heating and cooling, and evaporation and precipitation, all ultimately controlled by solar radiation and linked to atmospheric circulation. Major surface ocean currents are wind driven, created by...

North Atlantic Sea Surface Temperatures and Pelagic Ecosystems

Ruddiman 1989

There are clear linkages between variability in physical aspects of oceanic systems and variability in biological aspects of pelagic marine ecosystems as measured by biomass and other properties at various temporal and spatial scales Mann and Lazier 1996 . McGowen 1990 pointed out that the complex structure and function of pelagic marine ecosystems made mathematical modeling of fluxes of energy and matter difficult. Rather, McGowen 1990 suggested a phenomenological approach as an alternative...

Proxies Of Climate

The third major theme of paleoclimatology is the use of proxies of environmental parameters to reconstruct climates of the past. Because paleoclimatologists cannot revisit the past to observe or measure climate parameters, they have developed a diverse arsenal of proxy tools such as emu eggshell geochemistry to attack complex problems of climate change. Before examining the classes of proxy tools, I discuss briefly a few of the more important sources of climate data from historical and...

Principles of Paleoclimatology

theories too do not evolve piecemeal to fit facts that were there all the time. Rather, they emerge together with the facts they fit from a revolutionary reformulation of the preceding scientific tradition, a tradition within which the knowledge-mediated relationship between the scientist and nature was not quite the same. INTRODUCTION A MULTIDISCIPLINARY APPROACH IN PALEOCLIMATOLOGY The outback of western Australia has been home for millions of years to endemic flightless birds such as the...

Low Latitude Climatic Cycles in the Indian Ocean Monsoon Equatorial Pacific and Atlantic Upwelling

Tropical and subtropical oceanic pelagic ecosystem variability is also characterized by orbital frequencies during the past few million years. Moreover, tropical and subtropical oceanic biomes probably play a reciprocal role in long-term climate change by regulating atmospheric-ocean carbon fluxes during large-scale climatic oscillations. For example, near-surface productivity changes, which vary seasonally due to wind-induced upwelling, also vary over glacial-interglacial time scales. Glacial...

The Deepsea Record Of Orbital Climate Change

Testing orbital theory requires a more continuous temporal record of climate than that provided by the snapshot-like sea-level record of coral-reef tracts. The advent of deep-sea sediment coring, foraminiferal micropaleontology, and stable isotope geochemistry provided continuity of climate indicators. Continuity is a prerequisite for tests of periodicity, an inherent part of Milankovitch's theory. The fairly continuous record of ocean history afforded by micropaleonto-logical data yielded two...

Dating and Correlation of Climate Change The Geological Time Scale

All paleoclimatology is firmly rooted in the standard geologic time scale accepted by most geologists who study earth history. Table 2-3 lists the major subdivisions of the geological stratigraphic column. Throughout most of this book, the focus is on climates of the Cenozoic the last 66 million years of earth history especially the past 5 million years of Pliocene and Quaternary history. References will also be made to long-term climate history, which are described in general surveys of...

Indicator Species and Fossil Assemblages

Plankton And Paleoclimatology

The species and assemblages of about a dozen major groups are used routinely in paleoclimatology, and many more minor fossil groups are used less commonly figure 2-8, table 2-7 . What makes a species a good proxy of climate parameters Although the answer to this question varies widely from group to group, Coope 1977 provides five attributes of species of Coleoptera beetles that also apply to most other groups evolutionary stability, morphological complexity species-specific fossilizable...

Major Forcing Mechanisms

Two central goals of paleoclimatology are to document patterns of past climate change that is, the how and when of climate change and to infer why climate changes. It is therefore important to conceptualize the distinction between reconstructed patterns of climate change, which may be exceptionally well-documented by multiple-proxy data in several regions, and the processes that may have produced those patterns. The processes that cause climate to change are both external and FIGURE 2-4...

Radiometric Dating

Several naturally occurring, unstable isotopes of certain elements are frequently used to determine the age of climate-related phenomena. The age of geological material can be computed from the ratio of parent to daughter isotopes using the radioisotopes' half-life, the time it takes for half the original number of atoms to decay. Radioactive iso-topic decay occurs when an isotope of an element undergoes spontaneous emission of either electromagnetic radiation or particles. Two radioactive...

Contemporary Issues in Climate Change The Role of Paleoclimatology

We attach the utmost importance to a full understanding of the physical, chemical, and biological processes by which subtle changes in insolation are amplified to induce long-term changes in global climate. For this, a knowledge of the sequences of events and the exact timing of forcings and of the climate responses in various parts of the earth system is essential. As the Royal Mathematician living near Prague, in what is now the Czech Republic, Johannes Kepler's job in the early seventeenth...

Reciprocity Climate Change and Biological Processes

Global Biome

A second reason to focus on biology is the reciprocity between climate change and biological processes. Just as climate change can have severe impacts on biotic systems, biotic activity likewise influences climate. The study of climate history thus requires an understanding of the inherent role that organisms play in biogeochemical processes that link the atmosphere and ocean in the flow of energy and matter. An obvious example of how biotic activity regulates climate is the role in the storage...

The Fossil Record Sensu Latu

Why stress a biological focus in paleoclimatology, a field traditionally viewed as a discipline of the physical sciences There are four overarching reasons to bring a biological focus into our attempts to understand climate change. The first reason relates to the prior discussion of tropical glacial-age paleoclimatology. Much if not most evidence for climate change is based on information derived from biological sources preserved in the fossil record. In paleoclimatology, fossil record refers...

Preface

Most scientists can recall an incident, probably insignificant at the time it happened, when their interest in natural history was stirred. I had two such moments. First, when I was six or seven, I asked my dad how the immense rocks had found their way into my Connecticut back yard. He explained that they had been carried there by great glaciers thousands of years ago. I never gave a second thought to the rocks and glaciers, nor to the climate changes that ultimately were responsible for them,...

Hutchinson Niche Hypervolume

Hutchinson Niche Hypervolume

In his classic paper Homage to Santa Rosalia,'' G.E. Hutchinson 1959 asked the simple question Why are there so many species '' Hutchinson's papers spawned an explosion in theoretical ecology that reached a zenith in seminal publications by Robert MacArthur 1972 MacArthur and Wilson 1967 , Robert May 1981 , and many other ecologists see Cody and Diamond 1975 . Much of this effort was devoted to expressing mathematically the relationships between competing species and populations and to...

Niche in Paleoclimatology

In paleoclimatology, the niche concept is manifested as one of the discipline's most fundamental principles embodied in the concept of an indicator species. A useful indicator species is one whose abundance and distribution or sometimes simply its presence or absence in time and space are limited by physical parameters related to climate. The niche variables that, to the evolutionary ecologist, were agents of natural selection among individuals to the paleoclimatologist become the critical...

Obliquity or Tilt

Distribution Sunlight Over The Earth

Today the earth's axis of rotation is tilted about 23.5 relative to the ecliptic plane and is gradually declining at a rate of about 0.5 yr. The inclination of the axis of Venus is, by contrast, tilted only 3 . When earth is tilted toward the sun, there is summer in one hemisphere and winter in the other. Earth's tilt has varied over long time scales between 22 to 25 , owing to planetary effects on the position of the ecliptic in space. One complete cycle of obliquity takes about 41 ka. The...

Astronomical Tuning

Tuning'' represents a novel and somewhat controversial method to date and correlate paleoclimatic events related to the orbital theory of climate change. This theory holds that gravitational influences on earth's orbital eccentricity, tilt, and precession affect seasonal and geographical distribution of solar radiation and global climate. Geologists have for more than a century tried to establish whether the timing of orbital cycles as determined by celestial mechanics e.g., Berger et al. 1984,...

Communities and Ecosystems

Communities of plants and animals are defined as groups of species that have evolved to coexist and interact in a variety of ways. Communities represent a higher level of biotic integration than populations and species. The concept of community in ecology incorporates the biological elements i.e., species but usually excludes the physical parameters that influence individuals and populations living in the community. A community is therefore not solely defined by the spatial dimensions of the...

Stable Isotopes

Stable isotope ratios of oxygen 18O 16O , carbon 13C 12C , hydrogen deuterium, 2H 1H, in ice cores , and to a lesser extent nitrogen 15N 14N probably comprise the single most important family of paleoclimate tools used to reconstruct past climates. A proper treatment of stable isotope paleoclimatology would require volumes the following brief section on the terminology of stable isotopes gives the basic tenets of the stable isotope method and a foundation for many applications described in...