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Glaciations and thermodynamic

26 sábado Nov 2016

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Earth system is maintained in a state so far away from TE (Equilibrium thermodynamics) despite the natural direction towards mixing matter and depleting sources of free energy. The Exchange of energy and mass with the surroundings is a critical component that allows systems to evolve away from TE without violating the second law of thermodynamics. The evolutionary direction of the Earth systems away from TE can thus be understood as a consequence o the MEP principle (Maximum Entropy Production).

Life affects climate through its role in the carbón and water cycles and through such mechanisms as albedo, evapotranspiration, cloud formation and weathering.

The glacial and inerglacial periods  of the Quaternary Ice Age were named after characteristic geological features.

Geological time scale:

ERA                              PERIOD                   EPOCA                          Millions of years ago

CENOZOICO 

 

 Quaternary       

Holocene                       0.01————today

Pleistocene                   2.0————-0.01

 

Tertiary   

Pliocene                       5.1————-2

Miocene                        24.6————5.1

Oligocene                      38.0———–24.6

Eocene                           54.9———–38

Paleocene                      65.0———-54.9

MESOZO———-248————65

PALEOZOIC    

Premian                         286———–248

Carboniferous             360———–286

Devorian                       408———–360

Silurian                         438———–408

Ordovician                    505———–438

Cambrian                      545———–505

 

Nomenclaturte of Quaternary glacial cycles

1ST             Würm                    glacial period      12-71 Ka

                   Riss-Würm            interglacial           115-130

2ND           Riss                         glacial period       130-200

                   Mindel-Riss          interglacial           374-424

3RD-6TH   Mindel                   glacial period       424-478                  

                    Günz-Mindel        interglacial           478-563

7TH-8TH    Günz                      glacial peiod         621-676

 

The second ice age, and posibly most severe, is estimated to have ocurred from 850 to 635 Ma agen, in the Neoproterozoic Era. A minor series of glaciations occurred from 460 Ma to 430 Ma. There were extensive glaciations from 350 to 250 Ma. The current ice age, called the Quaternary glaciation, has seen more or less extensive glaciation on 40.000 and later, 100.000 year cycles.

The planet seems to have three main setting and colon:

“snowball”: when planet´s entrie surface is frozen over

“icehouse”: when there is some permanent ice

“greenhouse”: when tropical temperaturas extend to the poles

  • 4 to 2.1 billion years ago: snowball Earth, the Huronian glaciation is the oldest ice age we know about. Home only to unicelular life-forms.
  • 850 to 630 million years ago: deep freeze, the evolution of large cells, and possibly also multicelular organisms, this would have sucked CO2 out of the atmosphere, weakening the greenhouse effect and thus lowering global temmperatures.
  • 460 to 430 million years ago: mass extinction, the late Ordovician period, the plants becoming common over the course of the Silurian period.
  • 360 to 260 million years ago: plants invade the land, expansión of land plants that followe the Cryogenian. As plants spread over the planet, they aboserved CO2, from the atmosphere and releaxed oxygen.
  • 14 million yearse ago: Antarctica freezes ago, increased weathering, which sucked CO2, out of the Atmosphere and reduced the greenhouse effect.
  • 50 million years ago: lateste advance of the ice, the main trigger for the Quaternary glaciation was the continuing fall in the level of CO2 in the atmosphere due to the weathering of the Himalayas.
  • 000 to 12.000 yearse ago: our ice age, the cool temperaturas of the Quaternary may have allowed our brains to become much larger than those of our of hominid ancestors. As the glacial period drew to a close and temperaturas began to rise, there were two final cold snaps.

 

Changes in the sun´s energy affect how much energy reaches Earth´s system

Changes in the sun´s intensivity have influenced Earth´s climate in the past.  Changes in Earth´s orbit have had a big impact in climate over tens to  hundreds of thousands of years. Primary cause of past cycles of ice ages, long periods of cold temperatures (ice ages), as well as shorter interglacial periods  of relatively warmer temperatures.  Changes in solar energy continue to affect climate. Changes in the shape of Earth´s orbit as well as the tilt and position of Earth´s axis affect temperature on very long timescales (tens to hundreds of thousands of years), and therefore cannot explain the recent warming. Sunlight reaches Earth, it can be reflected or absorbed, snow and clouds tend to reflect most sunlight, darker objects and surfaces, like the ocean, forests, or soil, tend to absorb more sunlight. Earth as a whole has an albedo of about 30%, meaning that 70% of the sunlight that reaches the planet is absorbed. Absorbed sunlight warms Earth´s land, water, and atmosphere. Processes such as deforestation, reforestation, desertification, and urbanization often contribute to changes in climate in the places they occur. Human activities have generally increased the number of aerosol particles in the atmosphere. Reductions in overall aerosol emissions can therefore lead to more warming.

 

Life

Affects climate through its role in the carbón and water cycles and through such mechanisms as albedo, evapotranspiration, cloud formation, and weathering:

  • Glaciation 2,3 billion years ago triggered by the evolution of oxygenic photosynthesis, which depleted the atmosphere of the greenhouse gas carbón dioxide and introduced free oxygen.
  • Another glaciation 300 million years ago ushered in by long-term burial of descomposition-resistant detritus of vascular land-plants (creating a carbón sink and forming coal)
  • Termination of the Paleocene-Eocene Thermal Maximum 55 million years ago by flourishing marine phytoplankton.
  • Reserval of global warming 49 million years ago by 800.000 years of arctic azolla blooms.
  • Global cooling over hte past 40 million years driven by the expansión of grass-grazer ecosystems.

Human and natural sources:

Methane: is produced through both natural and human activities. Natural wetlands, agricultural activities and fossil fuel extraction and transport all emit CH4. CH4 concentrations increased sharply during most of the 20th century and are now more than-and-a-half times preindustrial levels.

Nitrous oxide: Nitrous oxide is produced through natural and human activities, mainly through agricultural activities and natural biological processes. Concentrations of N20 have risen approximately 20% since the start of the Industrial Revolution.

Water vapor: is the most abundant greenhouse gas and also the most important in terms of its contribution to the natural greenhouse effect, despite having a short atmospheric lifetime.

Tropospheric ozone (O3), which also has a short atmospheric lifetime, is a potent greenhouse gass.

 

Thermodynamic and Earth´s Climate

The particular ítem or collection of ítems tht is  interesting is called the system, everything that´s not included in the system , everything that´s not included in the system we´ve defined is called the surroundings.

There are three types of systems in thermodynamics: open, closed and isolated.

  • An open system: can Exchange both energy and matter with its surroundings.
  • A closed system: on the other hand, can Exchange only energy with its surroundings, not matter.
  • Isolated system : is one that cannot Exchange either matter or energy with its surroundings.

The total amount of energy in the universo, and in particular, it states that this total amount does not change. The First Law of Thermodynamics states that energy cannot be created or destroyed. It can only be change formo r be transferred from one object to another. Heat that doesn´t do work goes towards increasing the randomness of the Universe. The degree of randomness or disorder in a system is called its entropy. We can state a biology-relevant versión of the Second Law of Thermodynamics: every energy transfer that takes place will increase the entropy of the universo and reduce the amount of usable energy available to do work. In other words, any process, such as a chemical reaction or set of connected reactions, wil proceed in a direction that increases the oerall entropy of the Universe.

The cells are organized into tissues, and the tissues into organs; and  entire body maintains a carefull system of transport, exchange, and commerce that keeps the live. Chemical energy from complex molecules such as glucose and converting it into kinetic energy, a large fraction of the energy from fuel sources is simply transformed into heat. Much of it dissipates into the surrounding environment.

Earth´s atmosphere is far from thermodynamic equilibrium (TE). Entropy can be use as a measure for the lack of gradients and free energy. By depleting gradients and sources of free energy, these processes are directed towards the state of thermodynamic equilibrium (TE) at which the entropy of the system and its surroundings is maximized. The temperatura of the gas refers to the mean kinetic energy of the molecules, pressure describes the average intensity by which the molecules collidle with the walls of the volumen, and density measures the average number of molecules per unit volume. The most probable macroscopic state by definition is the state of máximum entropy, as stated by

Boltzman´s equation:   S= K log W,   S is the entroy and W the statical weight of a macrostate

The distinction between macroscopic and microscopic dynamics applies to understanding the large-scale behaviour of environmental systems and ecosystems.

Strong atmospheric circulation and the global cycles of wáter and carbón require engines to continuosly. Solar radiation also provides the photochemical energy to drive photosynthesis, which in turn provides the major source of free energy to drive geochemical cycles within the Earth system. States that thermodynamic process in non-equilibrium systems asume steady states at which their rates of entropy production are maximized.

Using the estándar thermodynamic definition of entropy change,

dS = dQ/T, extra increase in entropy of dS = dQ(1/Tb-1/Ta) results in an overall increase of the entropy of the whole system as stated by the second law (dS >0)

 

Some scientists think nowadays that we are living in Anthropocene Epoch and human influence is important. “Global Glacier recession continues”. A natural glacial may have seen just before to the Industrial Revolution, as a result of high late Holocene (the last 11.000 years on Earth) CO2 and the low orbital of the Earth, corrent interglacial climate would likely continue for another 50.000 years, making this an unisually long interglacial period.

 

Bibliography:

  • Wikipedia
  • Bethan Davies. antarcticglaciers.org. 2016
  • UC. Davis ChemWiki, “A system and its surroundings”.2015
  • Melillo, Jerry M., Terese Richmong, and Gary W.Yohe, Eds. “Climate Change Impacts in the United States: The Third National Climate Assesment”. 2014
  • Reece, J.B., Urry, L.A., Cain, M.L, Wasserman, S.A., Minorsky, P.V., and Jackson, R.B. “The laws of energy transformation”. Campbell biology (10th ed., pp 143-145) 2011.
  • Michael Marshall , “The history of ice on Earth”.2010
  • A.Kleidon, “A basic introduction to the thermodynamics of the Earth system far from equilibrium and máximum entropy production”. 2010
  • National Research Council. The National Academies Press, Washington, “Advancing the Science of Climate Changes”. 2010
  • Van Andel, Tjeerd H. “New Views on an Old Planet: A History of Global Change”. Cambridge UK. 1994

 

Relation links:

The laws of thermodynamic

Glaciation

 

 

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Climate change

13 domingo Nov 2016

Posted by in CIENCIA, Geofisica

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climate-change

Climate changes prior to the Industrial Revolution in the 1700s can be explained by natural causes, such as changes in solar energy, volcanic eruptions, and natural changes in greenhouse gas (GHG) concentrations. Recent climate changes, cannot be explained by natural causes alone. It is especially warming since the mid-20th century. It is extremely likely that human activities have been the dominant cause of that warming.

Earth´s temperature depends on the balance between energy entering and leaving the planet´s system. When incoming energy from the sun is absorbed by the Earth system, Earth warms. When the sun´s energy is reflected back into space, Earth avoids warming. When absorbed energy is released back into space, Earth cools.

Many factors, both natural and human, can cause changes in Earth´s energy balance, including:

  • Variations in the sun´s energy reaching Earth
  • Changes in the reflectivity of Earth´s atmosphere and surface
  • Changes in the greenhouse effect, which affects the amount of heat reained by Earth´s atmosphere.

Climate change is a change in the statistical distribution of weather patterns when that change lasts for an extended period of time: decades to millions of years.

Climate change is caused by:

  • factors such as biotic processes, variations in solar radiation received by Earth,plate tectonics, and volcanic eruptions

  • certain human activities have also been identified as significant causes of recent climate change, often referred to as global warming.

Are used observations and theoretical models, based on geological evidence from:

  • Borehole temperature profiles

  • Cores removed from deep accumulations of ice, floral and faunal records

  • Glacial and periglacial processes

  • Stable-isotope and other analysis of sediment layers

  • Records of past sea levels

PHYSICAL EVIDENCE

  • Historical and archaeological evidence: oral history and historical documents can offer insights into past changes in the climate. Climate change effects have been linked to the collapse of various civilizations.
  • Glaciers: are considered among the most sensitive indicators of climate change. Their size is determinate by a mass balance between snow input and melt output. As temperature warm, glaciers retreat unless snow precipitation increases to make up for the additional melt. The most significant climate processes since the middle to late Pliocene are the glacial and interglacial cycles. The present interglacial period has lasted about 11.700 years.
  • Arctic sea ice loss: Satellite observations show that Arctic sea ice is now declining at a rate of 13.3 percent per decade, relative to the 1891 to 2010 average.
  • Vegetation: a change in the type, distribution and coverage of vegetation may occur given a change in the climate. Some changes in climate may result in increases precipitation and warmth. Vegetation stress, rapid plant loss and desertification in certain circumstances are radical changes.
  • Pollen analysis: different groups of plants have pollen with distinctive shapes and surface textures. Changes in the type of pollen found in different layers of sediment in lakes, bogs, or river deltas indicate changes in plant communities.
  • Cloud cover and precipitation: scientists have plublished evidence o increased cloud cover over polar regions, as predicted by climate models. Estimated global land precipitation increases by approximately 2% over the course of the 20th century.
  • Dendroclimatology: is the analysis of tree ring growth patterns to determine past climate variations.
  • Ice cores: The air trapped in bubbles in the ice can also reveal the CO2 variations o the atmosphere from the distant past, well before modern environmental influences. The changes in CO2 over may millennia, and continues to provide valuable information about the differences between ancient and modern atmospheric conditions.
  • Animals: different species o beetles tend to be found under different climatic conditions. Knowledge of the present climatic range of the different species, and the age of the sediments in which remains are found, past climatic conditions may be inferred.
  • Sea level change: in the early Pliocene, global temperatures were 1-2ºC warmer than the present temperature, yet sea level was 15-25 meters higher than today.

CAUSES

Energy is received from the Sun the rate at which it is lost to space determine equilibrium temperature and climate of Earth. This energy is distributed around the globe by winds, ocean currents, and other mechanisms to affect the climates of different regions.

Forcing mechanisms can be “internal” o “external”. Internal forcing mechanisms are natural processes within the climate system itself. External forcing mechanisms can be natural or anthropogenic.

        1.  Internal forcing mechanisms: scientists generally define the five components of earth´s climate system to include atmosphere, hydrosphere, cryosphere, lithosphere and biosphere.

Ocean variability: the ocean is a fundamental part of the climate system, some changes in it occurring at longer timescales than in the atmosphere, as it has hundreds of times more mass and thus very high thermal inertia. Short-term fluctuations such as the Niño-Southern Oscillation, the Pacific decadal oscillation, the North Atlantic oscillation, and the Arctic oscillation, represent climate variability rather than climate change. On longer time-scales, alterations to ocean processes such as thermohaline circulation play a key role in redistributing heat by carrying out a very slow and extremely deep movement of water and the long-term redistribution of heat in the world´s oceans.

Life: affects climate through its role in the carbon and water cycles and through such mechanisms as albedo, evapotranspiration, cloud formation, and weathering.

  1. External forcing mechanisms:

Orbital variations: variations in Earth´s orbit lead to changes in the seasonal distribution of sunlight reaching the Earth´s surface and how it is distributed across the globe. The three types of orbital variations are variations in Earth´s eccentricity;

    • Changes in the tilt angle o Earth´s axis of rotation

    • Precession of Earth´s axis

Combined together, these produce Milankovitch cycles, which have a large impact on climate and are notable por their correlation to glacial and interglacial periods.

Solar output: variations in solar activity during the last several centuries based on observations o sunspots and beryllium isotopes. Three to our billion years ago, the Sun emitted only 70% as much power as it does today. Over the following approximately 4 billion years, the energy output of the Sun increases and atmospheric composition changed. The Great Oxygenation Event-oxygenation of the atmosphere around 2.4 billion years ago.

Volcanism: the eruptions considered to be large enough to affect the Earth´s climate on a scale of more than I year the ones that inject over 100.000 tons of SO2, into the stratosphere (sulfuric acid), causing cooling, blocking the transmission of solar radiation to the Earth´s surface for a period o a few years. Volcanoes are also part of carbon cycle. Over very long time periods, they release carbon dioxide from the Earth´s crust and mantle, counteracting the uptake by sedimentary rocks and other geological carbon dioxide sinks.

Plate tectonics: the motion o tectonic plates reconfigures global land and ocean areas and generates topography. The position of the continents determines the geometry of the oceans and therefore influences patterns of ocean circulation. The size of continents is also important. Because of the stabilizing effect of the oceans on temperature, yearly temperature variations are generally lower in coastal areas than they are inland. A larger supercontinent will therefore have more area in which climate is strongly seasonal than will several smaller continents or islands.

Human influences: in the context of climate variation, anthropogenic factors are human activities which affect the climate. The scientific consensus on climate change is “that climate is changing and these changes are in large part caused by human activities. Of most concern in these anthropogenic factors are:

  • Increase in CO2 levels due to emissions from fossil fuel combustion

  • Aerosols

  • CO2 from cement manufacture

  • Ozone depletion

  • Animal agriculture and deforestation.

Radiative Forcing: is a measure of the influence of a particular factor on the net change in Earth´s energy balance. On average, a positive radiative forcing tends to warm the surface of the planet, while a negative forcing tends to cool the surface. GHGs have a positive forcing because they absorb energy radiating from Earth´s surface, rather than allowing it to be directly transmitted into space. Aerosols, can have a positive or negative radiative forcing, depending on how they absorb and emit heat or reflect light. GHGs has increased between 1990 and 2009 a 27,5%, carbon dioxide (CO2) is responsible for 80%., also there are contribution of metano (CH4) and chlorofluorocarbons (CFCs).

The greenhouse effect: greenhouse gases like water vapor (H2O), carbon dioxide (CO2), and methane (CH4), absorb energy, slowing or preventing the loss of heat to space. GHGs act like a blanket, making Earth warmer than it would otherwise be.

Since the Industrial Revolution began around 1750, human activities have contributed substantially to climate change by adding CO2, and other heat-trapping gases to the atmosphere. These greenhouse gas emissions have increased the greenhouse effect and caused Earth´s surface temperature to rise. The most important GHGs directly emitted by humans include carbon dioxide (CO2), methane (CH4), nitrous oxide (N20), and several others.

Carbon dioxide is the primary greenhouse gas that is contributing to recent climate change. CO2 is absorbed and emitted naturally as part of the carbon cycle: most of the chemicals that make up living tissue contain carbon. Carbon enters atmosphere as carbon dioxide from respiration and combustion. Carbon dioxide is absorved by producers to make carbohydrates in photosynthesis.

Respiration CH2O + O2—————CO2 + H20

Photosynthesis CO2 + H2O + LUZ—CH2O + O2

Animals feed on the plant passing the carbon compounds along the food chain. Most of the carbon they consume is exhaled as carbon dioxide formed during respiration. The animals and plants eventually die, carbon in their bodies is returned to the atmosphere as carbon dioxide. When descomposition is blocked. The plant and animal material may then be available as fossil fuel in the future combustion.

Feedbacks: climate feedbacks amplify o reduce direct warming and cooling effects. Positive feedbacks that amplify changes, feedbacks that counteract changes are called negative feedbacks; feedbacks are associated with changes in surface reflectivity, clouds, water vapor, and the carbon cycle. The melting of Arctic sea ice is another example of a positive climate feedback. Some types of clouds cause a negative feedback (warming temperatures can increase the amount or reflectivity of these clouds, reflecting more sunlight back into space, cooling the surface of the planet). Other types of clouds, however, contribute a positive feedback.

Bibliography:

  • Wikipedia

  • NASA, “Climate change and global warming”
  • Arthur N. Strahler (1970), “Physical geography”, Ed. Jhon Wikey and Sons. INC
  • America´s Climate Choices (2010), “Advancing the Science of Climate Change”, Washington, D.C.: The National Academies Press.
  • Katie Peek (2016), “How will Climate change us”, September Scientific American

Relation links:

  • NASA

http://www.nasa.gov/press-release/nasa-releases-detailed-global-climate-change-projections/

  • CSIC

http://digital.csic.es/handle/10261/33470