Abrupt millennial-scale changes in intensity of Southern Hemisphere westerly winds during marine isotope stages 2–4

Whittaker, Thomas E; Hendy, Chris H.; Hellström, John

doi:10.1130/g31827.1

Cited by 71 publications

(88 citation statements)

References 34 publications

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“…Vertical dashed lines depict the timing of Heinrich stadials in the North Atlantic (Hemming, 2004). ations in local summer insolation intensity on orbital timescales, if such forcing is important. Therefore, this finding of a mismatch between glacier extent and summer intensity indicates that other mechanisms are responsible for controlling variability in local climate and supports the concept that fluctuations in New Zealand's climate, and thus glaciers, are driven largely by factors other than local summer insolation intensity Shulmeister et al, 2010a;Whittaker et al, 2011;De Deckker et al, 2012;Ryan et al, 2012;Putnam et al, 2013aPutnam et al, , 2013b.…”

Section: Discussionsupporting

confidence: 69%

“…Progress has been made with regard to establishing the wider geographical spread and timing of Antarctic climate signals, particularly during the latter part of the last glaciation, in terrestrial locations Putnam et al, 2010aPutnam et al, , 2013aWhittaker et al, 2011) as well as in marine settings (Barrows and Juggins, 2005;Kaiser et al, 2005;Pahnke and Zahn, 2005;Pahnke and Sachs, 2006;De Deckker et al, 2012). But data remain sparse prior to Marine Isotope Stage 2 (MIS 2) in terrestrial localities due to the limitations of radiocarbon dating, as well as to the destructive effects of multiple glaciations on the landscape.…”

Section: Introductionmentioning

confidence: 98%

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High-precision 10 Be chronology of moraines in the Southern Alps indicates synchronous cooling in Antarctica and New Zealand 42,000 years ago

Kelley

Kaplan

Schaefer

et al. 2014

Earth and Planetary Science Letters

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Section: Discussionsupporting

confidence: 69%

Section: Introductionmentioning

confidence: 98%

High-precision 10 Be chronology of moraines in the Southern Alps indicates synchronous cooling in Antarctica and New Zealand 42,000 years ago

Kelley

Kaplan

Schaefer

et al. 2014

Earth and Planetary Science Letters

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“…5.1-6.3 • C to achieve the mapped ice limits, when precipitation is unchanged from present. Quantitative estimates of regional changes in precipitation rate during the LGM remain poorly constrained, although evidence from climate modelling (Drost et al, 2007;Rojas et al, 2009), previous glacier modelling ( Golledge et al, 2012), carbon isotopes in speleothems (Whittaker et al, 2011), and diatoms in maar deposits indicates that drier than present conditions prevailed across New Zealand at this time. Precipitation reductions of up to 25 % from present require additional decreases in temperature by up to 0.8 • C to achieve the LGM glacial geometries in the central North Island (Fig.…”

Section: Last Glacial Maximum Climate In New Zealandmentioning

confidence: 99%

“…Lorrey et al, 2012) related to the drivers of change. Estimates of precipitation changes during the LGM are even more scarce, and often qualitative (Whittaker et al, 2011). Increasing the number and spatial coverage of quantitative palaeoclimate reconstructions will help to resolve these issues.…”

Section: Introductionmentioning

confidence: 99%

The Last Glacial Maximum in the central North Island, New Zealand: palaeoclimate inferences from glacier modelling

et al. 2016

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Abstract. Quantitative palaeoclimate reconstructions provide data for evaluating the mechanisms of past, natural climate variability. Geometries of former mountain glaciers, constrained by moraine mapping, afford the opportunity to reconstruct palaeoclimate, due to the close relationship between ice extent and local climate. In this study, we present results from a series of experiments using a 2-D coupled energy balance-ice flow model that investigate the palaeoclimate significance of Last Glacial Maximum moraines within nine catchments in the central North Island, New Zealand. We find that the former ice limits can be simulated when present-day temperatures are reduced by between 4 and 7 • C, if precipitation remains unchanged from present. The spread in the results between the nine catchments is likely to represent the combination of chronological and model uncertainties. The majority of catchments targeted require temperature decreases of 5.1 to 6.3 • C to simulate the former glaciers, which represents our best estimate of the temperature anomaly in the central North Island, New Zealand, during the Last Glacial Maximum. A decrease in precipitation of up to 25 % from present, as suggested by proxy evidence and climate models, increases the magnitude of the required temperature changes by up to 0.8 • C. Glacier model experiments using reconstructed topographies that exclude the volume of post-glacial (< 15 ka) volcanism generally increased the magnitude of cooling required to simulate the former ice limits by up to 0.5 • C. Our palaeotemperature estimates expand the spatial coverage of proxy-based quantitative palaeoclimate reconstructions in New Zealand. Our results are also consistent with independent, proximal temperature reconstructions from fossil groundwater and pollen assemblages, as well as similar glacier modelling reconstructions from the central Southern Alps, which suggest air temperatures were ca. 6 • C lower than present across New Zealand during the Last Glacial Maximum.

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“…A study by Whittaker et al (2011) demonstrates an inverse relation between d 13 C and amount of annual rainfall; a wetter climate will be linked to a lower d 13 C recorded in nearsurface cements due to an open system with high soil moisture, and thus less plant stress, higher biological activity in the soil zone, and isotopic equilibrium between infiltrating fluid and soil CO 2 (Harmon et al 2004).…”

mentioning

confidence: 99%

Influence of climate and dolomite composition on dedolomitization: insights from a multi-proxy study in the central Oman Mountains

Vandeginste

John

2012

Journal of Sedimentary Research

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Dedolomitization is an important diagenetic process that can yield information on the history of paleo-fluids in a given aquifer or outcrop, and by extension it offers a window into past hydrologic conditions. Dedolomitization is also relevant economically as it can alter the porosity and permeability of carbonates, thus affecting reservoir quality. Despite considerable research, the process of dedolomitization is still not entirely understood. Here, new findings from the central Oman Mountains highlight the importance of dolomite chemistry and fluctuating climate on dedolomitization. Petrographic, mineralogical, and geochemical data from both altered and pristine dolomite hosted in Jurassic carbonate rocks from the Sahtan Group and outcropping at Wadi Mistal in the Jebel Akhdar tectonic window reveal two dolomite bodies with different characteristics, stratabound and fault-related dolostone. The (ferroan) dolomite crystals are larger in the fault-related dolostone, whereas the (non-ferroan) dolomite crystals are smaller in the stratabound dolostone. Petrography reveals a complex suite of alteration textures, including pristine dolomite, recrystallized dolomite, and calcitized dolomite (dedolomite). Iron oxides are present pervasively in the altered rocks, and different alteration textures co-occur in the same sample. Relative to unaltered dolomite in this outcrop, the recrystallized dolomite is characterized by similar positive carbon isotope values but less negative oxygen isotope values, and the calcitized dolomite is characterized by even less negative oxygen isotope values and more negative carbon isotope values. Based on field data and petrography, two phases of alteration are evident, an earlier dedolomitization event affecting the stratabound dolomite only, and a more pervasive Pleistocene-Holocene alteration phase associated with surface weathering that affected both the fault-related dolomite and to a lesser extent the stratabound dolomite. Stable isotope results further suggest that the more recent subaerial weathering phase happened under two alternating climate regimes: dedolomitization was triggered by meteoric fluids that interacted with soil-related carbon during humid climatic period(s), whereas recrystallization of ferroan fault-related dolomite happened during more arid climatic period(s) with less developed soils and lower fluid-rock interaction. These results suggest that weathering of ferroan fault-related dolomite can lead to formation of goethite and recrystallized, non-stoichiometric dolomite (with a reset stable oxygen isotope signature), and sometimes to dedolomitization.

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Abrupt millennial-scale changes in intensity of Southern Hemisphere westerly winds during marine isotope stages 2–4

Cited by 71 publications

References 34 publications

High-precision 10 Be chronology of moraines in the Southern Alps indicates synchronous cooling in Antarctica and New Zealand 42,000 years ago

High-precision 10 Be chronology of moraines in the Southern Alps indicates synchronous cooling in Antarctica and New Zealand 42,000 years ago

The Last Glacial Maximum in the central North Island, New Zealand: palaeoclimate inferences from glacier modelling

Influence of climate and dolomite composition on dedolomitization: insights from a multi-proxy study in the central Oman Mountains

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