Pliocene palaeoclimates: Past climates as possible analogues of mid-twenty-first century climate

Zubakov, V.A.; Борзенкова, И. И.

doi:10.1016/0031-0182(88)90110-1

Cited by 57 publications

(14 citation statements)

References 29 publications

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“…The temperature changes shown in Figure 4b for the North Atlantic are comparable to those deduced for the early Pliocene, some 3 m.y. ago [Cronin, 1988;Dowsett and Poore, 1991], and the high-latitude temperature changes over land are broadly similar to those reconstructed by Zubakov and Borzenkova [1988]. This raises the question whether increased ocean transports were responsible for the relative warmth of that time period, and thus the inability of Milankovitch variations to produce ice sheet growth (e.g., Figure 1).…”

Section: Kutzbach Et Al's Experiments Indicates That the Thermohalinementioning

confidence: 60%

Increased ocean heat transports and warmer climate

1991

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We investigated the effect of increased ocean heat transports on climate in the Goddard Institute for Space Studies (GISS) general circulation model (GCM). The increases used were sufficient to melt all sea ice at high latitudes, and amounted to 15% on the global average. The resulting global climate is 2øC warmer, with temperature increases of some 20øC at high latitudes, and IøC near the equator. The warming is driven by the decreased sea ice/planetary albedo, a feedback which would appear to be instrumental for producing extreme high-latitude amplification of temperature changes. Resulting hydrologic and wind stress changes suggest that qualitatively, for both the wind-driven and thermohaline circulation, the increased transports might be self-sustaining. As such, they would represent a possible mechanism to help account for the high-latitude warmth of climates in the Mesozoic and Tertiary, and decadal-scale climate fluctuations during the Holocene, as well as a powerful feedback to amplify other climate forcings. It is estimated that ocean transport increases of 50-70% would have been necessary to reproduce the warmth of various Mesozoic (65-230 m.y. ago) climates without changes in atmospheric composition, while the 15% increase used in these experiments would have been sufficient to reproduce the general climatic conditions of the Eocene (40-55 Ma). A companion experiment indicates that increased topography during the Cenozoic (0-65 Ma) might have altered the surface wind stress in a manner that led to reduced heat transports; this effect would then need to be considered in understanding the beginning of ice ages. Colder climates, or rapid climate perturbations, might have been generated with the aid of such altered ocean transports. The large high-latitude amplification associated with ocean heat transport and sea ice changes differs significantly from that forecast for increased trace gases, for which water vapor increase is the primary feedback mechanism. The different signatures might allow for discrimination of these different forcings; e.g., the warming of the 1930s looks more like the altered ocean heat transport signal, while the warming of the 1980s is more like the trace gas effect. The actual change of ocean heat transport and deepwater circulation both in the past and in the future represents a great uncertainty.

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Section: Kutzbach Et Al's Experiments Indicates That the Thermohalinementioning

confidence: 60%

Increased ocean heat transports and warmer climate

1991

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“…Likewise, important oceanic fronts in the Southern Ocean were situated significantly closer to the Antarctic continent during the mid‐Pliocene. Seasonality was also decreased relative to today in many regions, resulting in the “warm equable climate” ascribed to the Pliocene by so many previous workers [ Zubakov and Borzenkova , 1988, 1990].…”

Section: Introductionmentioning

confidence: 99%

Middle Pliocene sea surface temperature variability

et al. 2005

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[1] Estimates of sea surface temperature (SST) based upon foraminifer, diatom, and ostracod assemblages from ocean cores reveal a warm phase of the Pliocene between about 3.3 and 3.0 Ma. Pollen records and plant megafossils, although not as well dated, show evidence for a warmer climate at about the same time. Increased greenhouse forcing and altered ocean heat transport are the leading candidates for the underlying cause of Pliocene global warmth. Despite being a period of global warmth, this interval encompasses considerable variability. Two new SST reconstructions are presented that are designed to provide a climatological error bar for warm peak phases of the Pliocene and to document the spatial distribution and magnitude of SST variability within the mid-Pliocene warm period. These data suggest long-term stability of low-latitude SST and document greater variability in regions of maximum warming.

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“…[5]; 3) оптимум плиоцена, 4,3-3,3 млн л .н . [5,65]; 4) опти мум последнего межледниковья, 127-125 тыс . лет [13]; 5) максимум последнего оледене ния, 21-19 тыс .…”

Section: обсуждение результатовunclassified

History of sea ice in the Arctic basin: Lessons from the past for future

Борзенкова

2016

Lëd i sneg

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The process of the sea ice formation in the Arctic Ocean is analyzed for the period of the last 65 million years, i.e. from the Paleocene to the present time. Appearance of sea ice in the high latitudes is demonstrated to be caused by the negative trend in global temperatures due to decreasing of the CO2 concentration in the ancient atmosphere. Formation of seasonal and perennial ice cover in the limited area near the Pole could take place during the mid-Neogene period, about 12–13 Ma ago. However, areas of the sea icing could be obviously changed for this time during periods of the climate warming and cooling. Permanent sea ice had been formed in the early Pleistocene, i.e. about 2.0–1.8 Ma ago only. Paleoclimatic reconstructions, based on the indirect data and modeling simulation for the Holocene optimum (10–6 ka ago) and for the Last Interglacial period (the isotopic substage in the marine cross-section 5e, about 125–127 ka ago) had shown that rising of global temperatures by 1.0–1.5 °C resulted in strong decreasing of the sea ice area, and the perennial ice cover became the seasonal one. Relatively small changes in the incoming solar radiation originating during the spring-summer time due to the orbital factors played the role of a trigger for onset of the melting process. Further on, the process could be enhanced owing to difference in the albedo between the ice cover and open water. Recently, the rapid shortening of the sea ice area is noted, and in some parts of the Arctic Ocean the area is twice cut down as compared with the normal. In 2015, the record low area of the winter sea ice was observed, and therewith the maximum of the ice area shifted to the earlier period (by 15 days) as compared with the period of 1981–2010. The winter fluctuations of the sea ice areas are as much important as the summer ones, since they are the best indicators of the present-day global warming. Thus, it can be supposed that some mechanism of replacing the perennial sea ice by the seasonal ones has been started up, that is the natural process of transition from seasonal ices to the next stage that is the ice-free Arctic. On the assumption that increasing of the CO2 concentration will continue despite the efforts to reduce emissions of greenhouse gases into the atmosphere, and the radiation forcing will approach to doubling of the CO2 content, one of the scenarios of the past can be realized now.

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Pliocene palaeoclimates: Past climates as possible analogues of mid-twenty-first century climate

Cited by 57 publications

References 29 publications

Increased ocean heat transports and warmer climate

Increased ocean heat transports and warmer climate

Middle Pliocene sea surface temperature variability

History of sea ice in the Arctic basin: Lessons from the past for future

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