Pliocene climate
Encyclopedia
During the Pliocene
epoch (5.3 Ma to 2.6 Ma) climate became cooler and drier, and seasonal, similar to modern climates.
The global average temperature in the mid-Pliocene (3.3 Ma–3 Ma) was 2–3°C higher than today, global sea level 25m higher and Northern hemisphere ice sheet ephemeral before the onset of extensive glaciation over Greenland that occurred in the late Pliocene around 3 Ma.
The formation of an Arctic ice cap is signaled by an abrupt shift in oxygen
isotope
ratios and ice-rafted cobbles in the North Atlantic and North Pacific ocean
beds. Mid-latitude glaciation
was probably underway before the end of the epoch. The global cooling that occurred during the Pliocene may have spurred on the disappearance of forests and the spread of grasslands and savannas.
During the Pliocene
the earth climate system response shifted from a period of high frequency-low amplitude oscillation dominated by the 41.000 year period of Earth's obliquity
to one of low frequency-high amplitude oscillation dominated by the 100.000 year period of the Orbital eccentricity
characteristic of the Pleistocene glacial-interglacial cycles.
The equatorial pacific ocean sea surface temperature gradient was considerably lower than it is today, mean sea surface temperature in the east were substantially warmer than today but similar in the west, this condition has been described as a permanent El Niño state or El Padre
Panama seaway closure :
The closure of the Panama seaway (13 Ma–2.5 Ma) increased the salinity contrast between Pacific and Atlantic ocean and the northward oceanic heat transport, warmer water increased snowfall and possibly Greenland ice sheet
volume, however model simulation suggest reduced ice volume due to increased ablation at the edge of the ice sheet under warmer conditions.
Collapse of permanent El Niño :
A permanent El Niño state existed in the early-mid Pliocene
, warmer temperature in the eastern equatorial pacific increased water vapor greenhouse effect and reduced the area covered by highly reflective stratus clouds thus decreasing the albedo
of the planet, propagation of El Niño effect through planetary waves may have warmed the polar region and delayed the onset of the northern hemisphere glaciation.
Therefore the appearance of cold surface water in the east equatorial pacific around 3 millions years ago may have contributed to global cooling and modified global climate response to Milankovitch cycles
.
Uplift of the Rocky mountains and Greenland west coast:
Uplift of the Rocky mountains and Greenland west coast may have cooled the climate due to jet stream deflection and increased snowfall due to higher surface elevation.
Carbon dioxide :
Carbon dioxide
concentration during the mid Pliocene has been estimated at around 400 ppmv from 13C/12C ratio in organic marine matter and stomatal density of fossilized leaves, decreasing carbon dioxide levels during late Pliocene may have contributed substantially to global cooling and the onset of northern hemisphere glaciation.
extent oscillated at the 40Kyr period of Earth's obliquity, ice sheet collapse occurred when global average temperature were 3°C warmer than today and carbon dioxide concentration 400 ppmv and resulted in open waters in the Ross Sea
.
Global sea level fluctuation associated with ice sheet collapse were probably of up to 7 meters for west antarctic and 3 meters for east antarctic.
Model simulations are consistent with reconstructed ice sheet oscillations and suggest a progression from smaller to larger west antarctic ice sheet in the last 5 Million years, intervals of ice sheet collapse are much more common in the early-mid Pliocene (5Ma–3Ma), after 3Ma intervals with modern or glacial ice volume became longer and collapse occurs only at times when warmer global temperature coincide with strong austral summer insolation anomalies.
warm period is considered a potential analog of future climate. The intensity of the sunlight reaching the earth, the global geography, and carbon dioxide
concentrations were similar to present. Furthermore many mid-Pliocene species are extant helping paleotemperature proxies
calibration.
Model simulations of mid-Pliocene climate produce warmer conditions at middle and high latitudes, as much as 10–20°C warmer than today above 70°N. They also indicate little temperature variation in the tropics. Model-based biomes are generally consistent with Pliocene paleobotanical data indicating a northward shift of the Tundra and Taiga and an expansion of Savanna and warm-temperate forest in Africa and Australia.
Pliocene
The Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...
epoch (5.3 Ma to 2.6 Ma) climate became cooler and drier, and seasonal, similar to modern climates.
The global average temperature in the mid-Pliocene (3.3 Ma–3 Ma) was 2–3°C higher than today, global sea level 25m higher and Northern hemisphere ice sheet ephemeral before the onset of extensive glaciation over Greenland that occurred in the late Pliocene around 3 Ma.
The formation of an Arctic ice cap is signaled by an abrupt shift in oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
isotope
Isotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
ratios and ice-rafted cobbles in the North Atlantic and North Pacific ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
beds. Mid-latitude glaciation
Glacier
A glacier is a large persistent body of ice that forms where the accumulation of snow exceeds its ablation over many years, often centuries. At least 0.1 km² in area and 50 m thick, but often much larger, a glacier slowly deforms and flows due to stresses induced by its weight...
was probably underway before the end of the epoch. The global cooling that occurred during the Pliocene may have spurred on the disappearance of forests and the spread of grasslands and savannas.
During the Pliocene
Pliocene
The Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...
the earth climate system response shifted from a period of high frequency-low amplitude oscillation dominated by the 41.000 year period of Earth's obliquity
Axial tilt
In astronomy, axial tilt is the angle between an object's rotational axis, and a line perpendicular to its orbital plane...
to one of low frequency-high amplitude oscillation dominated by the 100.000 year period of the Orbital eccentricity
Orbital eccentricity
The orbital eccentricity of an astronomical body is the amount by which its orbit deviates from a perfect circle, where 0 is perfectly circular, and 1.0 is a parabola, and no longer a closed orbit...
characteristic of the Pleistocene glacial-interglacial cycles.
The equatorial pacific ocean sea surface temperature gradient was considerably lower than it is today, mean sea surface temperature in the east were substantially warmer than today but similar in the west, this condition has been described as a permanent El Niño state or El Padre
Global cooling and Northern hemisphere glaciation onset
Several mechanisms have been proposed to explain global cooling after 3 Ma and the onset of extensive northern hemisphere glaciation.Panama seaway closure :
The closure of the Panama seaway (13 Ma–2.5 Ma) increased the salinity contrast between Pacific and Atlantic ocean and the northward oceanic heat transport, warmer water increased snowfall and possibly Greenland ice sheet
Greenland ice sheet
The Greenland ice sheet is a vast body of ice covering , roughly 80% of the surface of Greenland. It is the second largest ice body in the world, after the Antarctic Ice Sheet. The ice sheet is almost long in a north-south direction, and its greatest width is at a latitude of 77°N, near its...
volume, however model simulation suggest reduced ice volume due to increased ablation at the edge of the ice sheet under warmer conditions.
Collapse of permanent El Niño :
A permanent El Niño state existed in the early-mid Pliocene
Pliocene
The Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...
, warmer temperature in the eastern equatorial pacific increased water vapor greenhouse effect and reduced the area covered by highly reflective stratus clouds thus decreasing the albedo
Albedo
Albedo , or reflection coefficient, is the diffuse reflectivity or reflecting power of a surface. It is defined as the ratio of reflected radiation from the surface to incident radiation upon it...
of the planet, propagation of El Niño effect through planetary waves may have warmed the polar region and delayed the onset of the northern hemisphere glaciation.
Therefore the appearance of cold surface water in the east equatorial pacific around 3 millions years ago may have contributed to global cooling and modified global climate response to Milankovitch cycles
Milankovitch cycles
Milankovitch theory describes the collective effects of changes in the Earth's movements upon its climate, named after Serbian civil engineer and mathematician Milutin Milanković, who worked on it during First World War internment...
.
Uplift of the Rocky mountains and Greenland west coast:
Uplift of the Rocky mountains and Greenland west coast may have cooled the climate due to jet stream deflection and increased snowfall due to higher surface elevation.
Carbon dioxide :
Carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
concentration during the mid Pliocene has been estimated at around 400 ppmv from 13C/12C ratio in organic marine matter and stomatal density of fossilized leaves, decreasing carbon dioxide levels during late Pliocene may have contributed substantially to global cooling and the onset of northern hemisphere glaciation.
West antarctic ice sheet
West Antarctic Ice SheetWest Antarctic Ice Sheet
The West Antarctic Ice Sheet is the segment of the continental ice sheet that covers West Antarctica, the portion of Antarctica on the side of the Transantarctic Mountains which lies in the Western Hemisphere. The WAIS is classified as a marine-based ice sheet, meaning that its bed lies well...
extent oscillated at the 40Kyr period of Earth's obliquity, ice sheet collapse occurred when global average temperature were 3°C warmer than today and carbon dioxide concentration 400 ppmv and resulted in open waters in the Ross Sea
Ross Sea
The Ross Sea is a deep bay of the Southern Ocean in Antarctica between Victoria Land and Marie Byrd Land.-Description:The Ross Sea was discovered by James Ross in 1841. In the west of the Ross Sea is Ross Island with the Mt. Erebus volcano, in the east Roosevelt Island. The southern part is covered...
.
Global sea level fluctuation associated with ice sheet collapse were probably of up to 7 meters for west antarctic and 3 meters for east antarctic.
Model simulations are consistent with reconstructed ice sheet oscillations and suggest a progression from smaller to larger west antarctic ice sheet in the last 5 Million years, intervals of ice sheet collapse are much more common in the early-mid Pliocene (5Ma–3Ma), after 3Ma intervals with modern or glacial ice volume became longer and collapse occurs only at times when warmer global temperature coincide with strong austral summer insolation anomalies.
Mid Pliocene and future climate
The mid PliocenePliocene
The Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...
warm period is considered a potential analog of future climate. The intensity of the sunlight reaching the earth, the global geography, and carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
concentrations were similar to present. Furthermore many mid-Pliocene species are extant helping paleotemperature proxies
Proxy (climate)
In the study of past climates is known as paleoclimatology, climate proxies are preserved physical characteristics of the past that stand in for direct measurements , to enable scientists to reconstruct the climatic conditions that prevailed during much of the Earth's history...
calibration.
Model simulations of mid-Pliocene climate produce warmer conditions at middle and high latitudes, as much as 10–20°C warmer than today above 70°N. They also indicate little temperature variation in the tropics. Model-based biomes are generally consistent with Pliocene paleobotanical data indicating a northward shift of the Tundra and Taiga and an expansion of Savanna and warm-temperate forest in Africa and Australia.
See also
- PliocenePlioceneThe Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...
- El Niño
- Five Million Years of Climate Change