Marine Isotopic Stage 11
Encyclopedia
Interglacial
periods that occurred during Pleistocene
times have been recently put under investigation, in order to better understand our present and future climates. In fact, paleoclimatic interpretations often depends on observations drawn from the study of modern/historical processes. In order to better estimate the ”natural range” of climatically important mechanisms, it seems crucial to attempt detailed comparisons of the present interglacial (i.e., the Holocene
) with previous warm periods of the Quaternary
, such as Marine isotopic stage
11 (hereafter “MIS 11” for the sake of brevity). Similar orbital configurations and comparable atmospheric greenhouse gas
concentrations (considering only the period before the beginning of the Industrial Revolution, i.e. 1800 AD ca.) have led to the suggestion that MIS 11 is a suitable, possibly the best, geological analogue for the natural development of Holocene and future climate. Another candidate was MIS 5, but several characteristics do not fit the present conditions.
MIS 11 spans from 420 to 360 ka , and represents the longest and warmest interglacial interval of the last 500 kyr. In fact, it shows the highest-amplitude deglacial warming in the last 5 Myr and possibly lasted twice the other interglacial stages. MIS 11 is characterized by overall warm sea-surface temperatures in high latitudes, strong thermohaline circulation
, unusual blooms of calcareous plankton
in high latitudes, higher sea level than the present, coral reef
expansion resulting in enlarged accumulation of neritic carbonates, and overall poor pelagic carbonate preservation and strong dissolution in certain areas.
concentration during MIS 11 was possibly similar to that documented in the pre-industrial period, but not especially high when compared to other interglacial periods (for example, CO2 concentration was probably higher during MIS 9. In addition, a peculiar feature of MIS 11 is that an early CO2 peak, usually associated to the deglaciation in response to increasing temperatures, is not detected.
Seemingly, the long-lasting interglacial conditions that are documented during MIS 11 depend on the peculiar interplay between CO2 concentration and insolation. In fact, during periods of both eccentricity
and precession
minima, even small variations in total insolation
might lead the control of climate to greenhouse gasses, in particular CO2.
) accompanied increased reef carbonate production. Calcium carbonate production peaked in subpolar and subtropical oceans, reflecting a shift in plankton ecology from diatom
s to calcareous plankton due to changes in seawater temperatures, which were apparently warmer at low latitudes. The increased production of carbonate in either continental shelves
and mid-latitude open-ocean environments may partly explain the high rates of carbonate sediments dissolution during MIS 11 throughout ocean basins, such as the Indian and Pacific. Indeed, increases in regional carbonate productivity can be only explained by increased carbonate dissolution in other (source) areas. Another explanation for the presence of barrier-reef tracts at low latitudes during MIS 11 is that tropical continental shelves were (at least partly) flooded in response to a major marine transgression (see below).
, Bermuda
and the Bahamas, as well as uplifted reef terraces in Indonesia
, suggest that global sea level reached as much as twenty metres above the present . During MIS 11, δ18O records show isotopic depletions that are consistent with a sea-level highstand, but temperature effect cannot be confidently disentangled from glacioeustasy. Moreover, the collapse of at least one major ice sheet has to be inferred in order to produce similar high sea-levels, nevertheless, the stability of these ice sheets is one of the main questions in climate-change research: in fact, controversial geologic evidences suggest that present-day polar ice sheets might have been disrupted (or drastically shrunk) during previous Pleistocene interglacials. The increased sea level requires reduction in modern polar ice sheets and is consistent with the interpretation that both the West Antarctica
and the Greenland
ice sheets were absent, or at least greatly reduced, during MIS 11. However, similar conditions would have led to much lighter δ18O values than the present, in contrast to what observed in oxygen isotope records worldwide.
Noteworthy, MIS 11 developed just after one of the most “heavy” Pleistocene δ18O glacials (MIS 12). According to some Authors, MIS 12 is likely to represent a “minimum” within the 400-kyr cyclicity (which is apparently “stretched” into ca. 500-kyr cycles in the Pleistocene), same as the MIS 24/MIS 22 complex (ca. 900 ka; Wang et al., 2004). In support to this inference is the fact that these dramatic glacial intervals are coincident with periods of major climate reorganisation, namely the “Mid-Brunhes Event” (Jansen et al., 1986) and the “Mid-Pleistocene Revolution” (Berger & Jansen, 1994), respectively.
Considering the variability in the astronomically-driven insolation, MIS 11 is the interval in which insolation is highly correlated with predicted near future situation. Using the 2-D Northern Hemisphere climate model to simulate climate evolution over MIS 11, MIS 5 and the future, it appears that climatic feature and length of MIS 11 are very similar to the present-future interglacial. This consideration may lead to the conclusion that actual interglacial period (begun 10 kyr) will continue for approximately 20-25 kyr.
Interglacial
An Interglacial period is a geological interval of warmer global average temperature lasting thousands of years that separates consecutive glacial periods within an ice age...
periods that occurred during Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....
times have been recently put under investigation, in order to better understand our present and future climates. In fact, paleoclimatic interpretations often depends on observations drawn from the study of modern/historical processes. In order to better estimate the ”natural range” of climatically important mechanisms, it seems crucial to attempt detailed comparisons of the present interglacial (i.e., the Holocene
Holocene
The Holocene is a geological epoch which began at the end of the Pleistocene and continues to the present. The Holocene is part of the Quaternary period. Its name comes from the Greek words and , meaning "entirely recent"...
) with previous warm periods of the Quaternary
Quaternary
The Quaternary Period is the most recent of the three periods of the Cenozoic Era in the geologic time scale of the ICS. It follows the Neogene Period, spanning 2.588 ± 0.005 million years ago to the present...
, such as Marine isotopic stage
Marine isotopic stage
Marine isotope stages , marine oxygen-isotope stages, or oxygen isotope stages , are alternating warm and cool periods in the Earth's paleoclimate, deduced from oxygen isotope data reflecting changes in temperature derived from data from deep sea core samples...
11 (hereafter “MIS 11” for the sake of brevity). Similar orbital configurations and comparable atmospheric greenhouse gas
Greenhouse gas
A greenhouse gas is a gas in an atmosphere that absorbs and emits radiation within the thermal infrared range. This process is the fundamental cause of the greenhouse effect. The primary greenhouse gases in the Earth's atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, and ozone...
concentrations (considering only the period before the beginning of the Industrial Revolution, i.e. 1800 AD ca.) have led to the suggestion that MIS 11 is a suitable, possibly the best, geological analogue for the natural development of Holocene and future climate. Another candidate was MIS 5, but several characteristics do not fit the present conditions.
MIS 11 spans from 420 to 360 ka , and represents the longest and warmest interglacial interval of the last 500 kyr. In fact, it shows the highest-amplitude deglacial warming in the last 5 Myr and possibly lasted twice the other interglacial stages. MIS 11 is characterized by overall warm sea-surface temperatures in high latitudes, strong thermohaline circulation
Thermohaline circulation
The term thermohaline circulation refers to a part of the large-scale ocean circulation that is driven by global density gradients created by surface heat and freshwater fluxes....
, unusual blooms of calcareous plankton
Plankton
Plankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...
in high latitudes, higher sea level than the present, coral reef
Coral reef
Coral reefs are underwater structures made from calcium carbonate secreted by corals. Coral reefs are colonies of tiny living animals found in marine waters that contain few nutrients. Most coral reefs are built from stony corals, which in turn consist of polyps that cluster in groups. The polyps...
expansion resulting in enlarged accumulation of neritic carbonates, and overall poor pelagic carbonate preservation and strong dissolution in certain areas.
MIS 11: warmer or colder than the present?
As stated above, MIS 11 is considered the warmest interglacial period of the last 500 kyr . Nevertheless, some issues concern the lack of evidence for the trends and degree of warming during this interval. Recent isotopic and planktonic faunal data sets from high-accumulation rate marine successions in the North and South Atlantic indicate that MIS 11 was not warmer, but even slightly cooler than the Holocene. According to these data, the warmest interglacial period was likely MIS 5, although it was shorter.Concentration of CO2
Carbon dioxideCarbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
concentration during MIS 11 was possibly similar to that documented in the pre-industrial period, but not especially high when compared to other interglacial periods (for example, CO2 concentration was probably higher during MIS 9. In addition, a peculiar feature of MIS 11 is that an early CO2 peak, usually associated to the deglaciation in response to increasing temperatures, is not detected.
Seemingly, the long-lasting interglacial conditions that are documented during MIS 11 depend on the peculiar interplay between CO2 concentration and insolation. In fact, during periods of both 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...
and precession
Precession
Precession is a change in the orientation of the rotation axis of a rotating body. It can be defined as a change in direction of the rotation axis in which the second Euler angle is constant...
minima, even small variations in total insolation
Insolation
Insolation is a measure of solar radiation energy received on a given surface area in a given time. It is commonly expressed as average irradiance in watts per square meter or kilowatt-hours per square meter per day...
might lead the control of climate to greenhouse gasses, in particular CO2.
Carbonate productivity
In shallow-water environments, the development of several major reef systems (such as the Great Barrier ReefGreat Barrier Reef
The Great Barrier Reef is the world'slargest reef system composed of over 2,900 individual reefs and 900 islands stretching for over 2,600 kilometres over an area of approximately...
) accompanied increased reef carbonate production. Calcium carbonate production peaked in subpolar and subtropical oceans, reflecting a shift in plankton ecology from diatom
Diatom
Diatoms are a major group of algae, and are one of the most common types of phytoplankton. Most diatoms are unicellular, although they can exist as colonies in the shape of filaments or ribbons , fans , zigzags , or stellate colonies . Diatoms are producers within the food chain...
s to calcareous plankton due to changes in seawater temperatures, which were apparently warmer at low latitudes. The increased production of carbonate in either continental shelves
Continental shelf
The continental shelf is the extended perimeter of each continent and associated coastal plain. Much of the shelf was exposed during glacial periods, but is now submerged under relatively shallow seas and gulfs, and was similarly submerged during other interglacial periods. The continental margin,...
and mid-latitude open-ocean environments may partly explain the high rates of carbonate sediments dissolution during MIS 11 throughout ocean basins, such as the Indian and Pacific. Indeed, increases in regional carbonate productivity can be only explained by increased carbonate dissolution in other (source) areas. Another explanation for the presence of barrier-reef tracts at low latitudes during MIS 11 is that tropical continental shelves were (at least partly) flooded in response to a major marine transgression (see below).
Global sea level & marine transgression
Beach deposits in AlaskaAlaska
Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...
, Bermuda
Bermuda
Bermuda is a British overseas territory in the North Atlantic Ocean. Located off the east coast of the United States, its nearest landmass is Cape Hatteras, North Carolina, about to the west-northwest. It is about south of Halifax, Nova Scotia, Canada, and northeast of Miami, Florida...
and the Bahamas, as well as uplifted reef terraces in Indonesia
Indonesia
Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...
, suggest that global sea level reached as much as twenty metres above the present . During MIS 11, δ18O records show isotopic depletions that are consistent with a sea-level highstand, but temperature effect cannot be confidently disentangled from glacioeustasy. Moreover, the collapse of at least one major ice sheet has to be inferred in order to produce similar high sea-levels, nevertheless, the stability of these ice sheets is one of the main questions in climate-change research: in fact, controversial geologic evidences suggest that present-day polar ice sheets might have been disrupted (or drastically shrunk) during previous Pleistocene interglacials. The increased sea level requires reduction in modern polar ice sheets and is consistent with the interpretation that both the West Antarctica
West Antarctica
West Antarctica, or Lesser Antarctica, one of the two major regions of Antarctica, is the part of the continent that lies within the Western Hemisphere including the Antarctic Peninsula.-Location and description:...
and the Greenland
Greenland
Greenland is an autonomous country within the Kingdom of Denmark, located between the Arctic and Atlantic Oceans, east of the Canadian Arctic Archipelago. Though physiographically a part of the continent of North America, Greenland has been politically and culturally associated with Europe for...
ice sheets were absent, or at least greatly reduced, during MIS 11. However, similar conditions would have led to much lighter δ18O values than the present, in contrast to what observed in oxygen isotope records worldwide.
Astronomical features
Unlike most other interglacials of the late Quaternary, MIS 11 cannot be explained and modelled solely within the context of Milankovitch forcing mechanisms. According to various studies, the MIS 11 interglacial period was longer than the other interglacial stages; moreover, the sustained interglacial warmth lasted as long as it did, because the eccentricity was low and the amplitude of the precessional cycle diminished, resulting in several fewer cold substages during this period and also induced an abrupt climate change at MIS 12–11 transition, the most intense of the past 500 kyr.Noteworthy, MIS 11 developed just after one of the most “heavy” Pleistocene δ18O glacials (MIS 12). According to some Authors, MIS 12 is likely to represent a “minimum” within the 400-kyr cyclicity (which is apparently “stretched” into ca. 500-kyr cycles in the Pleistocene), same as the MIS 24/MIS 22 complex (ca. 900 ka; Wang et al., 2004). In support to this inference is the fact that these dramatic glacial intervals are coincident with periods of major climate reorganisation, namely the “Mid-Brunhes Event” (Jansen et al., 1986) and the “Mid-Pleistocene Revolution” (Berger & Jansen, 1994), respectively.
Considering the variability in the astronomically-driven insolation, MIS 11 is the interval in which insolation is highly correlated with predicted near future situation. Using the 2-D Northern Hemisphere climate model to simulate climate evolution over MIS 11, MIS 5 and the future, it appears that climatic feature and length of MIS 11 are very similar to the present-future interglacial. This consideration may lead to the conclusion that actual interglacial period (begun 10 kyr) will continue for approximately 20-25 kyr.
See also
- proxiesProxy (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...
- PaleoclimatologyPaleoclimatologyPaleoclimatology is the study of changes in climate taken on the scale of the entire history of Earth. It uses a variety of proxy methods from the Earth and life sciences to obtain data previously preserved within rocks, sediments, ice sheets, tree rings, corals, shells and microfossils; it then...
- PaleothermometerPaleothermometerA paleothermometer is a methodology for determining past temperatures using a proxy found in a natural record such as a sediment, ice core, tree rings or TEX86.=...
- Ice coreIce coreAn ice core is a core sample that is typically removed from an ice sheet, most commonly from the polar ice caps of Antarctica, Greenland or from high mountain glaciers elsewhere. As the ice forms from the incremental build up of annual layers of snow, lower layers are older than upper, and an ice...
- DendrochronologyDendrochronologyDendrochronology or tree-ring dating is the scientific method of dating based on the analysis of patterns of tree-rings. Dendrochronology can date the time at which tree rings were formed, in many types of wood, to the exact calendar year...
- lake and ocean sedimentsSedimentSediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....
- AnthropoceneAnthropoceneThe Anthropocene is a recent and informal geologic chronological term that serves to mark the evidence and extent of human activities that have had a significant global impact on the Earth's ecosystems...
- Ice AgeIce ageAn ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...
- Timeline of glaciationTimeline of glaciationThere have been five known ice ages in the Earth's history, with the Earth experiencing the Quaternary Ice Age during the present time. Within ice ages, there exist periods of more severe glacial conditions and more temperate referred to as glacial periods and interglacial periods, respectively...
- Hoxnian Stage