Lecture 15: Paleoclimate
Terms in this set (31)
5 known ___ ___ in Earth's climate history.
542 Myr to present. Rich rock record, very layered and informative because it follows the Cambrian explosion. Earth's climate varied between conditions that support large-scale continental glaciation and those which are extensively tropical and lack permanent ice caps at the poles.
4.6 to 054 byr. Snowball Earth
five stages of snowball earth
key requirement for development of large scale ice sheets is the arrangement of continental land masses near or at the poles, due to __ ___
cretaceous thermal maximum
one of the hottest periods of the phanerozoic. about 100 Myr. global sea level reached up to 25 meters above current sea level. CO2 levels rose to over 1000 parts per million (compared to pre-industrial average of 280ppm). deep water of the ocean was 15-20 degrees warmer than now.
65 myr to present. post extinction of dinosaurs. Rock record is richer. Earth began to cool, entering global cool period (icehouse). antarctic ice sheets began forming in late Eocene. Northern ice sheets started to form in late Miocene.
2.6 myr ago to present. Strong correlation between temperature, ice sheet thickness, carbon dioxide, and sea level. Equilibrium between glacial and interglacial.
Ice Age. climate fluctuates between interglacial and glacial periods. Includes younger dryas. Greenhouse gas levels fell at the start of ice ages and rose during the retreat of the ice ages. Correlates with external forcing from Milankovitch cycles.
12,900-11,700ya an abrupt cold/dry episode. Presumably caused by a shift in fresh water circulation. Marks end of the Pleistocene and the beginning of the holocene
11,700 BCE to present day
Richest data set, can look at history of temperature with great detail. Current geological epoch. Has seen impact of human species, including written history, development of civilization, and overall significant transition toward urban living in the present
2.6 MYR to today. last stage of earth's history to contain pleistocene and holocene. Interglacial period.
___ ___ levels fell at the start of ice ages and rose during the retreat of ice sheets
correlates with external forcing from the Milankovitch cycles
Medieval Warm Period
950-1250 CE. time of relatively warm climate during the European Middle ages
marked by a strong correlation between global temperatures and the concentration of greenhouse gases
natural phenomenon in which large armadas of icebergs break off from glaciers and traverse the North Atlantic, leaving rocks of glacial origin in the marine sediments
ice rafted debris
icebergs contained rock mass, as they melted, material was dropped to the sea floor. Deposits can e found in marine sediment from North Atlantic Ocean
12,900 to 11,700 BCE. marks final event of pleistocene. abrupt climate change.
11,700 BCE to present day. current geological epoch. Interglacial period
seen growth and impacts o fate human species worldwide, including all its written history, development of major civilizations, and overall significant transition toward urban living in the present
increase in ocean mass
since the last glacial maximum (20kya) the melting of ice sheets and glaciers contributed to a net ____ ____ ___ __.
steric sea level
global sea level rises by thermal expansion caused by warming of the ocean
little ice age
1300-1850 CE. Brought cold winters to parts of Europe and North America. Farms and villages in Swiss Alps were destroyed by encroaching glaciers during mid 17th century. Canals and rivers in Great Britain were frequently frozen over.
human activity competes with geological forces. Affects climate, biodiversity at a global scale.
produced by interaction of cosmic rays with nuclei in the atmosphere. As one neutrino crosses Earth, absorption probability depends on its energy and on the amount of matter traversed, which directly relate to path length
Current global sea level rise
___ sea level rise is caused by thermal expansion, salinity variation
steric sea level
shallow section of water is heating up (thermal expansion), same mass of water, but it warmer so it occupies more space
Global isostatic rebound
causes relative sea level change by viscoelastic postglacial rebound of the solid earth
melting of ice sheets
transfers freshwater on land to the ocean, produces net increase in ocean mass