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Geomagnetic Field Effects on Living Systems
Published in Shoogo Ueno, Tsukasa Shigemitsu, Bioelectromagnetism, 2022
The glacial-interglacial cycle is mainly due to changes in the amount of solar radiation due to changes in the Earth’s orbit and axis of rotation. The phenomenon is so-called “Milankovitch cycles,” which is a theory that variations in eccentricity, axial tilt, and precession of the Earth resulted in cyclical variation in the solar radiation reaching the Earth, and that this orbital forcing strongly influenced the Earth’s climatic patterns (Milanković, 1941; Knezevic, 2010). It occurs in the three basic cycles of about 21, 41, and 100 kyr, but recently even the shorter thousands to hundreds of years of climate change are supposed to be affected by the GMF (Knezevic, 2010). By integrating these Milankovitch cycles with changes in the oxygen isotope ratio of marine microfossils called foraminifera in seafloor sediments (glacial-interglacial cycles), more detailed ages of seafloor sediments are determined, and consequently, the M–B boundary is estimated to be dated to 772.9 ka as mentioned above (Haneda et al., 2020).
Energy
Published in Vaughn Nelson, Kenneth Starcher, Wind Energy, 2018
Vaughn Nelson, Kenneth Starcher
Glacial and interglacial periods [14] of the Earth are due to the changes in the orbit and the spin axis, which affect the geographical and seasonal distribution of insolation by as much as 10–20%, but hardly affect the mean annual solar insolation. The eccentricity of the orbit changes from zero to six degrees over a cycle of around 100,000 years, the tilt of the spin axis varies from 22.1° to 24.5° over a cycle of around 41,000 years, and the day in the year when the Earth is closest to the sun varies over a cycle of around 20,000 years due to precession of the tilt axis. These insolation changes, over long periods, affect the building and melting of ice sheets. Interglacial periods tend to occur during periods of peak solar radiation in the summer in the Northern Hemisphere. Glacial periods tend to occur with the Earth closest to the sun in January, which means warmer winters and cooler summers in the Northern Hemisphere, resulting in the building of ice sheets. Due to these changes, the Earth should be entering another glacial period, except it will not happen due to climate change-A. Paleoclimate data also show periods of fairly fast climate changes to a new state, primarily due to positive feedbacks.
Climate Change
Published in Vaughn Nelson, Kenneth Starcher, Introduction to Bioenergy, 2017
Vaughn Nelson, Kenneth Starcher, Vaughn Nelson, Kenneth Starcher
Glacial and interglacial periods [1] of the Earth are due to the changes in the orbit and the spin axis, which affect the geographical and seasonal distribution of insolation by as much as 10%–20%, but hardly effect the mean annual solar insolation. The eccentricity of the orbit changes from 0° to 6° over a cycle of around 100,000 years, the tilt of the spin axis varies from 22.1° to 24.5° over a cycle of around 41,000 years, and the day in the year when the Earth is closest to the Sun varies over a cycle of around 20,000 years due to precession of the tilt axis. These insolation changes, over long periods, affect the building and melting of ice sheets. Interglacial periods tend to occur during periods of peak solar radiation in the summer in the northern hemisphere. Glacial periods tend to occur with the Earth closest to the Sun in January, which means warmer winters and cooler summers in the northern hemisphere, resulting in building of ice sheets. Due to these changes, the Earth should be entering another glacial period, except it will not happen due to climate change-A. Paleoclimate data also show periods of fairly fast climate changes to a new state, primarily due to positive feedbacks.
Geological field guides as educational tools: the Coorong, South Australia
Published in Australian Journal of Earth Sciences, 2019
Sea level curve for the past 130,000 years, in relation to Marine Isotope Stages 1 to 5, derived from observations of flights of coral terraces on the uplifting Huon Peninsula, Papua New Guinea; adapted from Lambeck and Chappell (2001). The thickness of the line of the curve is an expression of the degree of uncertainty of the calculated sea-levels. Numbers 1 to 5 refer to episodes of time (stages) defined by marine oxygen isotopes. The Last Glacial Maximum, when sea level was about 120 m lower than at present, is shown within Stage 2. The Last Interglacial warm period (within Stage 5) occurred about 130,000 to 120,000 years ago, when sea level was about 2 m higher than at present. The present interglacial warm period (Stage 1) has existed for little more than the past 10 000 years. The rapid rise in sea level during the transition from Stage 2 to Stage 1 is known as the Postglacial Marine Transgression. The last 10,000 years (approximately) constitutes the Holocene Epoch.
Geoheritage significance of three Pleistocene formations recording a succession of climates and sea levels on the Yalgorup Plain in southwestern Australia
Published in Australian Journal of Earth Sciences, 2019
Another consequence of the Western Australian coast marked north–south climate gradient is that Earth-axis precession and migration of the Tropic of Capricorn (V. Semeniuk, 1995) will change climate on a 22,000-year cycle from tropical warm to temperate cool, changing commensurably the biota at a given location. Herein, potentially, lies the reason for the changes in carbonate productivity and in foraminiferal assemblages of the Tims Thicket Limestone versus vs the Myalup Sand or the Kooallup Limestone. Combined with glacial/interglacial alternations, the sea level highstand during an interglacial coincided with changing climate, driven by Earth-axis precession (cf. V. Semeniuk, 2012). This produced an interglacial period having warm water (equivalent in climate latitude to Dongara today), then cool water (equivalent in climate latitude to Albany today), then warm water (equivalent in climate latitude to the Perth region today). This unique climate record, preserved in the limestone components of the Yalgorup Plain, is of global significance.
Distribution of surficial sediments in the ocean around New Zealand/Aotearoa. Part A: continental slope and deep ocean
Published in New Zealand Journal of Geology and Geophysics, 2019
Helen Bostock, Chris Jenkins, Kevin Mackay, Lionel Carter, Scott Nodder, Alan Orpin, Arne Pallentin, Richard Wysoczanski
The maps produced from the nzSEABED database show the textural patterns (percent mud, sand and gravel = total 100%) and carbonate content, (percent carbonate; versus non carbonate; Figure 3). The latter provides information about the source of the sediments with the carbonate providing information about the amount of biological material is produced in the water column by plankton, or on the seafloor by marine organisms and is typically carbonate-rich, while the non-carbonate component it primarily derived from the land, termed terrigenous material, due to reworking by wind and water (rainfall and rivers) into the oceans. In some regions of the seafloor authigenic material is also present. Authigenic minerals are precipitated at the sea floor, under specific environmental conditions and typically over long periods of time and include phosphate nodules, glauconite and polymetallic nodules. The sediments are referred to as modern, which indicates that they have been deposited under modern environmental conditions over the last ∼7000 years when sea level (Clement et al., 2013) and ocean currents have been similar to today. In other regions sediments are referred to as relict, which implies they were deposited >7000 years ago when sea level was lower and or other environmental conditions were different. Sea level fluctuates over glacial/interglacial cycles due to changes in the global ice volume. During the last glacial at ∼20,000 years ago, sea level was ∼120 m lower than the present (Lambeck et al., 2014) and vast areas of the continental shelf were subaerially exposed. This had a significant influence on the sediment transport across and along the continental shelf, and how much terrigenous sediment was transported to the deep ocean via submarine canyon systems (e.g. Carter and Carter, 1996; Carter et al., 2004).