Hemispheric sea ice distribution sets the glacial tempo

Lee, Jung‐Eun; Shen, Aaron; Fox‐Kemper, Baylor; Ming, Yi

doi:10.1002/2016gl071307

Cited by 8 publications

(5 citation statements)

References 33 publications

(53 reference statements)

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“…4 ), as determined from δ 18 O b , suggesting that sea ice likely aids in the initiation of major terminations. Furthermore, the overall increase in sea ice extent across the MPT is in accordance with outcomes from a recent modelling study 18 , which indicates that a cooler climate results in larger sea ice extent and an asymmetric sea ice response between hemispheres, leading to 100-ka G/IG cycles 18 . However, since there are, as yet, no Antarctic sea ice records available for the MPT, we cannot directly assess the interhemispheric relationship of sea ice growth.…”

Section: Discussionsupporting

confidence: 86%

“…Second, the SIS proposes a land versus sea ice hysteresis, with large sea ice extent across early deglaciations 2 . Recent modelling studies also suggest that the periodicity of G/IG cycles is linked to changes in the interhemispheric pattern of sea ice growth 18 . However, while modelling studies clearly suggest the likely importance of sea ice for controlling climate change across the MPT 1 , 2 , 17 , 18 , complementary high-resolution proxy-based reconstructions of sea ice dynamics are yet to be reported.…”

Section: Introductionmentioning

confidence: 99%

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Sea ice dynamics across the Mid-Pleistocene transition in the Bering Sea

et al. 2018

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Sea ice and associated feedback mechanisms play an important role for both long- and short-term climate change. Our ability to predict future sea ice extent, however, hinges on a greater understanding of past sea ice dynamics. Here we investigate sea ice changes in the eastern Bering Sea prior to, across, and after the Mid-Pleistocene transition (MPT). The sea ice record, based on the Arctic sea ice biomarker IP25 and related open water proxies from the International Ocean Discovery Program Site U1343, shows a substantial increase in sea ice extent across the MPT. The occurrence of late-glacial/deglacial sea ice maxima are consistent with sea ice/land ice hysteresis and land−glacier retreat via the temperature−precipitation feedback. We also identify interactions of sea ice with phytoplankton growth and ocean circulation patterns, which have important implications for glacial North Pacific Intermediate Water formation and potentially North Pacific abyssal carbon storage.

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Section: Discussionsupporting

confidence: 86%

Section: Introductionmentioning

confidence: 99%

Sea ice dynamics across the Mid-Pleistocene transition in the Bering Sea

et al. 2018

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“…The δ 18 O record for the time span 0.7 to 1.1 Ma does, in fact, contain a 100 kyr periodicity, but its spectral density is relatively low because of complex interferences between orbitally controlled insolation and terrestrial parameters such as weathering rates, atmospheric CO 2 budget and sea-ice distribution that strengthens other periodicities (e.g. 33 , 42 ). The 3 Myr δ 18 O record compiled by Bintanja and van de Wal 43 shows that larger amplitude excursions at a 100 kyrs periodicity already occur since about 1 Ma, and their modeling results suggest that this is due to the formation of large northern hemisphere ice sheets since that time.…”

Section: Discussionmentioning

confidence: 99%

100- kyr cyclicity in volcanic ash emplacement: evidence from a 1.1 Myr tephra record from the NW Pacific

Schindlbeck

Jegen

Freundt

et al. 2018

Sci Rep

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It is a longstanding observation that the frequency of volcanism periodically changes at times of global climate change. The existence of causal links between volcanism and Earth’s climate remains highly controversial, partly because most related studies only cover one glacial cycle. Longer records are available from marine sediment profiles in which the distribution of tephras records frequency changes of explosive arc volcanism with high resolution and time precision. Here we show that tephras of IODP Hole U1437B (northwest Pacific) record a cyclicity of explosive volcanism within the last 1.1 Myr. A spectral analysis of the dataset yields a statistically significant spectral peak at the ~100 kyr period, which dominates the global climate cycles since the Middle Pleistocene. A time-domain analysis of the entire eruption and δ18O record of benthic foraminifera as climate/sea level proxy shows that volcanism peaks after the glacial maximum and ∼13 ± 2 kyr before the δ18O minimum right at the glacial/interglacial transition. The correlation is especially good for the last 0.7 Myr. For the period 0.7–1.1 Ma, during the Middle Pleistocene Transition (MPT), the correlation is weaker, since the 100 kyr periodicity in the δ18O record diminishes, while the tephra record maintains its strong 100 kyr periodicity.

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“…Because of the open geometry and strong zonal winds of the Southern Ocean, Ekman transport can potentially move large volumes of sea ice across long distances, unlike the North Atlantic where the basin shape limits the ability to export sea ice, causing the meridional transport to be smaller (Goosse and Fichefet 1999;Shin et al 2003;Lee et al 2017). Thus, when low CO 2 cools the global atmosphere, sea ice forms more rapidly at high latitudes of the Southern Ocean and is transported further north, causing the high latitude Southern Ocean to transition from a net-freshening to a net-salinifying domain (Fig.…”

Section: Co 2 and Orbital Influencementioning

confidence: 99%

Response of a comprehensive climate model to a broad range of external forcings: relevance for deep ocean ventilation and the development of late Cenozoic ice ages

Galbraith

Lavergne

2018

Clim Dyn

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Over the past few million years, the Earth descended from the relatively warm and stable climate of the Pliocene into the increasingly dramatic ice age cycles of the Pleistocene. The influences of orbital forcing and atmospheric CO 2 on landbased ice sheets have long been considered as the key drivers of the ice ages, but less attention has been paid to their direct influences on the circulation of the deep ocean. Here we provide a broad view on the influences of CO 2 , orbital forcing and ice sheet size according to a comprehensive Earth system model, by integrating the model to equilibrium under 40 different combinations of the three external forcings. We find that the volume contribution of Antarctic (AABW) vs. North Atlantic (NADW) waters to the deep ocean varies widely among the simulations, and can be predicted from the difference between the surface densities at AABW and NADW deep water formation sites. Minima of both the AABW-NADW density difference and the AABW volume occur near interglacial CO 2 (270-400 ppm). At low CO 2 , abundant formation and northward export of sea ice in the Southern Ocean contributes to very salty and dense Antarctic waters that dominate the global deep ocean. Furthermore, when the Earth is cold, low obliquity (i.e. a reduced tilt of Earth's rotational axis) enhances the Antarctic water volume by expanding sea ice further. At high CO 2 , AABW dominance is favoured due to relatively warm subpolar North Atlantic waters, with more dependence on precession. Meanwhile, a large Laurentide ice sheet steers atmospheric circulation as to strengthen the Atlantic Meridional Overturning Circulation, but cools the Southern Ocean remotely, enhancing Antarctic sea ice export and leading to very salty and expanded AABW. Together, these results suggest that a 'sweet spot' of low CO 2 , low obliquity and relatively small ice sheets would have poised the AMOC for interruption, promoting Dansgaard-Oeschger-type abrupt change. The deep ocean temperature and salinity simulated under the most representative 'glacial' state agree very well with reconstructions from the Last Glacial Maximum (LGM), which lends confidence in the ability of the model to estimate large-scale changes in water-mass geometry. The model also simulates a circulation-driven increase of preformed radiocarbon reservoir age, which could explain most of the reconstructed LGM-preindustrial ocean radiocarbon change. However, the radiocarbon content of the simulated glacial ocean is still higher than reconstructed for the LGM, and the model does not reproduce reconstructed LGM deep ocean oxygen depletions. These ventilation-related disagreements probably reflect unresolved physical aspects of ventilation and ecosystem processes, but also raise the possibility that the LGM ocean circulation was not in equilibrium. Finally, the simulations display an increased sensitivity of both surface air temperature and AABW volume to orbital forcing under low CO 2 . We suggest that this enhanced orbital sensitivity contributed to the developm...

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Hemispheric sea ice distribution sets the glacial tempo

Cited by 8 publications

References 33 publications

Sea ice dynamics across the Mid-Pleistocene transition in the Bering Sea

Sea ice dynamics across the Mid-Pleistocene transition in the Bering Sea

100- kyr cyclicity in volcanic ash emplacement: evidence from a 1.1 Myr tephra record from the NW Pacific

Response of a comprehensive climate model to a broad range of external forcings: relevance for deep ocean ventilation and the development of late Cenozoic ice ages

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