Dansgaard-Oeschger Events
DO events are sudden rises in the earth’s past temperature as observed using proxies. Many of them were far more severe than what we’re living in now. In general, I’m leaving out most of the literature that talks about a 1470-year cycle for DO events, because that has been eclipsed by newer research showing that it’s more complex and that there’s a major oscillation on the order of 6,000 years.
Number of papers: 13
Magnitude and temporal evolution of Dansgaard–Oeschger event 8 abrupt temperature change inferred from nitrogen and argon isotopes in GISP2 ice using a new least-squares inversion — Earth and Planetary Science Letters, 2014; Orsi et al.
We present an independent surface temperature reconstruction, which allows us to test the relationship between δ18O ice and temperature, during Dansgaard–Oeschger event 8, 38.2 thousand yrs ago using new δ15N and δ40Ar data from the GISP2 ice core in Greenland. … We find that both temperature and δ18O increased in two steps of 20 and 140 yrs, with an overall amplitude of 11.80 ± 1.8 ◦C between the stadial and interstadial centennial-mean temperature.
A stratigraphic framework for abrupt climatic changes during the Last Glacial period based on three synchronized Greenland ice-core records: refining and extending the INTIMATE event stratigraphy — Quaternary Science Reviews, 2014; Rasmussen et al.
An updating and more rigorous accounting scheme for placing and comparing previous research, including new events and conclusions. Boring, but foundational, work.
Siple Dome ice reveals two modes of millennial CO2 change during the last ice age — Nature Communications, 2014; Ahn & Brook
Looking at ice cores, the authors asked whether CO2 played any role in the several cold “stadial” events in Greenland. They find “CO2 does not significantly change during the short Greenlandic stadial events, implying that the climate system perturbation that produced the short stadials was not strong enough to substantially alter the carbon cycle.”
Abrupt Climate Change at the End of the Last Glacial Period Inferred from Trapped Air in Polar Ice — Science, 1999; Sveringhaus & Brook
“Nitrogen and argon isotopes in trapped air in Greenland ice show that the Greenland Summit warmed 9 +/- 3°C over a period of several decades, beginning 14,672 years ago. Atmospheric methane concentrations rose abruptly over a roughly 50-year period and began their increase 20 to 30 years after the onset of the abrupt Greenland warming.”
Potential links between surging ice sheets, circulation changes, and the Dansgaard-Oeschger Cycles in the Irminger Sea, 60–18 Kyr — Paleoceanography and Paleo Climatology, 2000; van Kreveld et al.
“We also conclude that the abrupt stadial terminations, the D-O warming events, were tied to iceberg melt via abundant seasonal sea ice and brine water formation in the meltwater-covered northwestern North Atlantic. In the 1/1460-year frequency band, benthic δ18O brine water spikes led the temperature maxima above Greenland and in the Irminger Sea by as little as 95 years. Thus abundant brine formation, which was induced by seasonal freezing of large parts of the northwestern Atlantic, may have finally entrained a current of warm surface water from the subtropics and thereby triggered the sudden reactivation of the THC. In summary, the internal dynamics of the east Greenland ice sheet may have formed the ultimate pacemaker of D-O cycles.”
Sea ice variability in the southern Norwegian Sea during glacial Dansgaard-Oeschger climate cycles — Science Advances; Sadatzki et al.
“We present unprecedented empirical evidence that resolves the nature, timing, and role of sea ice fluctuations for abrupt ocean and climate change 32 to 40 thousand years ago, using biomarker sea ice reconstructions from the southern Norwegian Sea. Our results document that initial sea ice reductions at the core site preceded the major reinvigoration of convective deep-water formation in the Nordic Seas and abrupt Greenland warming; sea ice expansions preceded the buildup of a deep oceanic heat reservoir.”
Dansgaard-Oeschger cycles: Interactions between ocean and sea ice intrinsic to the Nordic seas, Paleoceanography and Paleo Climatology, 2000; Dokken et al.
“Here we present a new, high-resolution multiproxy marine sediment core monitoring changes in the warm Atlantic inflow to the Nordic seas as well as in local sea ice cover and influx of ice-rafted debris. In contrast to previous studies, the freshwater input is found to be coincident with warm interstadials on Greenland and has a Fennoscandian rather than Laurentide source. Furthermore, the data suggest a different thermohaline structure for the Nordic seas during cold stadials in which relatively warm Atlantic water circulates beneath a fresh surface layer and the presence of sea ice is inferred from benthic oxygen isotopes. This implies a delicate balance between the warm subsurface Atlantic water and fresh surface layer, with the possibility of abrupt changes in sea ice cover, and suggests a novel mechanism for the abrupt D-O events observed in Greenland ice cores.”
The Atlantic Meridional Overturning Circulation and Abrupt Climate Change — Annual Review of Marine Science; Jean Lynch-Stieglitz
“Abrupt changes in climate have occurred in many locations around the globe over the last glacial cycle, with pronounced temperature swings on timescales of decades or less in the North Atlantic. The global pattern of these changes suggests that they reflect variability in the Atlantic meridional overturning circulation (AMOC). This review examines the evidence from ocean sediments for ocean circulation change over these abrupt events. The evidence for changes in the strength and structure of the AMOC associated with the Younger Dryas and many of the Heinrich events is strong. Although it has been difficult to directly document changes in the AMOC over the relatively short Dansgaard-Oeschger events, there is recent evidence supporting AMOC changes over most of these oscillations as well.”
North Atlantic ocean circulation and abrupt climate change 2 during the last glaciation — Environmental Science, Geography, 2016; Henry et al.
“Here we examine a equence of climate and ocean circulation proxies throughout MIS3 at high resolution in a deep North Atlantic sediment core, combining the kinematic tracer Pa/Th with the most widely applied deep water-mass tracer. These indicators reveal that Atlantic overturning circulation was reduced during every cool northern stadial, with the greatest reductions during episodic iceberg discharges from the Hudson Strait, and that sharp northern warming followed reinvigorated overturning. These results provide direct evidence for the ocean’s persistent, central role in abrupt glacial climate change.”
Global atmospheric teleconnections during Dansgaard–Oeschger events — Nature Geoscience, 2016; Markle et al.
This is an interesting paper that links the DO events in the north with earlier weather events in the south, indicating that the ITCZ connects the two. “Here we use a high-resolution deuterium-excess record from West Antarctica to show that the latitude of the mean moisture source for Antarctic precipitation changed in phase with abrupt shifts in Northern Hemisphere climate, and significantly before Antarctic temperature change. This provides direct evidence that Southern Hemisphere mid-latitude storm tracks shifted within decades of abrupt changes in the North Atlantic, in parallel with meridional migrations of the intertropical convergence zone. We conclude that both oceanic and atmospheric processes, operating on different timescales, link the hemispheres during abrupt climate change.”
Coupled atmosphere-ice-ocean dynamics in Dansgaard-Oeschger events — Quaternary Science Reviews, 2019; Li and Born
This is a mediocre paper. The authors look at evidence that Dansgaard-Oeschger events are an unforced or “spontaneous” oscillation of the Northern Seas. They say “Finding the sweet spot is a matter of understanding when the subpolar region enters a feedback loop whereby changes in wind forcing, sea ice cover, and ocean circulation amplify and sustain perturbations towards cold (ice-covered) or warm (ice-free) conditions.”
The low-latitude monsoon climate during Dansgaard–Oeschger cycles and Heinrich Events — Quaternary Science Reviews, 2000; Leuschner & Sirocko
This is a pretty interesting paper linking the Indian Ocean monsoon cycle to the DO events. They show essentially that the world’s oceans and their oscillations are very connected.
An ice–climate oscillatory framework for Dansgaard–Oeschger cycles — Nature Reviews Earth and Environment, 2020; Menviel et al.
“Palaeoclimate observations indicate that the AMOC might be more sensitive to perturbations than climate models currently suggest.”
Next: Greenland