The North Atlantic's 1–2 kyr climate rhythm: Relation to Heinrich events, Dansgaard/Oeschger cycles and the Little Ice Age

Abstract

New evidence from deep-sea sediment cores in the subpolar North Atlantic demonstrates that a significant component of sub-Milankovitch climate variability occurs in distinct 1-2 kyr cycles. We have traced that cyclicity from the present to within marine isotope stage 5, an interval spanning more than 80 kyrs. The most robust indicators of the cycle are repeated increases in the percentages of two petrologic tracers, Icelandic glass and hematite-stained grains. Both are sensitive measures of ice rafting episodes associated with ocean surface coolings. The petrologic tracers exhibit a consistent relation to Heinrich events, implying that mechanisms forcing Heinrich events were closely linked to those forcing the cyclicity. Our records further suggest that Dansgaard/Oeschger events may be amplifications of the cycle brought about by the impact of iceberg (fresh water) discharges on North Atlantic thermohaline circulation. The tendency of thermohaline circulation to undergo threshold behavior only when fresh water input is relatively large may explain the absence of Dansgaard/Oeschger events in the Holocene and their long pacings (thousands of years) in the early part of the glaciation. Finally, evidence from cores near Newfoundland confirms previous suggestions that the Little Ice Age was the most recent cold phase of the 1-2 kyr cycle and that the North Atlantic tended to oscillate in a muted Dansgaard/Oeschger-like mode during the Holocene.

Millennial to multi‐decadal variability in the climate of southern Africa

“…Other details are as given in Figure 2 and Greenland (Holmgren et al, 1999). Ocean-floor sediment cores south of Greenland suggest the possible existence of pervasive cycles of oceanic variability at around 1500 years, both in surface waters and in the strength of North Atlantic deep water movements that continued over long periods of time extending into the Holocene (Bond et al, 1997(Bond et al, , 1999(Bond et al, , 2001Bianchi and McCave, 1999). A dominant signal in the δ 18 O record for Makapansgat is that induced by variability in the range 600-800 years.…”

Periodic 1.5 ka climate variations during MIS 2 in the belt of Southern Hemispheric westerlies

“…Alley et al (2001) explained this property of Arctic and Antarctic ice-core records with stochastic resonance-that is, the climate switches between warm and cold if a combination of a weak periodicity plus noise reach a certain threshold (the noise characteristic is of importance and summarizes all relevant factors). (Bond et al, 1999) with updated chronology (Obrochta et al, 2012). Implications for atmospheric circulations The 1.5 ka periodicity dominates MIS 2 and occurs with diminished power during the late MIS 3 at LPA.…”

Solar Arctic-Mediated Climate Variation on Multidecadal to Centennial Timescales: Empirical Evidence, Mechanistic Explanation, and Testable Consequences

“…10 See Bond et al (1997) and Bond et al (1999) for the discussion of the muted Dansgaard/ Oeschger-like mode during the Holocene. See also the distinction and clarification for rapid and abrupt oscillations during glacial times and the Holocene in Alley (2007) and Denton and Broecker (2008).…”

“…In the context of the proposed solar Arctic-mediated climate variation mechanism, it is assumed that the sea ice export is not exactly the same as freshwater export from the Arctic and that more sea ice export from the Arctic basin may be more related to colder conditions within the Arctic, not unlike the notable icerafting events and episodes seen throughout the Quaternary (e.g., Bond et al, 1997Bond et al, , 1999Vidal et al, 1997;Darby and Zimmerman, 2008;Hill et al, 2008; or counter-views and interpretations by Andrews et al, 2006), or in the summer of 1695 recently re-interpreted by Gil et al (2006), as well as the great salinity anomaly events of the 1970s, 1980s, and 1990s, modeled and discussed in Zhang and Vallis (2006). But importantly, it is recognized that extra exports of sea ice, episodic or otherwise, or a more continuous nature of the freshening and flushing of water from the Arctic basin to the northern North Atlantic basins (e.g., Condron et al 2009) would serve as key negative feedbacks for the MOC/THC oscillation.…”

“…The modeling study by Wu and Wood (2008) suggests that the recent freshening trend over the subpolar North Atlantic can be explained by a redistribution of freshwater within the Arctic and subpolar North Atlantic and that the redistribution was probably carried out by a perturbed ocean circulation in the subpolar seas and triggered by deep convection in the Labrador Sea. In the context of the proposed solar Arctic-mediated climate variation mechanism, it is assumed that the sea ice export is not exactly the same as freshwater export from the Arctic and that more sea ice export from the Arctic basin may be more related to colder conditions within the Arctic, not unlike the notable icerafting events and episodes seen throughout the Quaternary (e.g., Bond et al, 1997Bond et al, , 1999Vidal et al, 1997;Darby and Zimmerman, 2008;Hill et al, 2008; or counter-views (2007) suggest that the vigor of ISOW is controlled by the transport and characteristics of the Labrador Sea water farther to the west (Jungclaus et al, 2005). The correlation between TSI and the three-point smoothed grain-size index shown in Figure 2 has a correlation coefficient of r = -0.45, which even with the reduced degrees of statistical freedom would still constitute a significant correlation.…”