Glacial geomorphology of the Ahuriri River valley, central Southern Alps, New Zealand

Tielidze, Levan; Eaves, Shaun; Norton, Kevin; Mackintosh, Andrew

doi:10.1080/17445647.2021.1876777

Cited by 7 publications

(13 citation statements)

References 29 publications

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“…A detailed glacial geomorphological work relating to the Ahuriri study site is presented in Chapter 4 and Tielidze et al (2021). The study area selected for this thesis includes the upper 20 portion of the Ahuriri River catchment, spanning about 45 km from the headwater (Figure 2.1b).…”

Section: Locationmentioning

confidence: 99%

“…The lowest terminus limits used in this study is based on my ages from the terminal moraine features. Other glacier limits (e.g., marginal, headwall) were defined from a detailed glacial geomorphological map (Tielidze et al, 2021) and high-resolution aerial imagery. For the palaeo glacier area uncertainty I used a buffer method which is broadly adopted for modern glacier mapping (e.g., Granshaw and Fountain 2006;Tielidze and Wheate, 2018).…”

Section: Approach Used In This Thesismentioning

confidence: 99%

“…Here I follow the same approach. To derive estimates of the present-day ELA, I used recently mapped modern glacier outlines from the Ahuriri River valley (Tielidze et al, 2021) along with a medium resolution (15 m) DEM (Columbus et al, 2011) and applied the AAR automatic approach (Pellitero et al, 2015) with the same ratio (0.62-0.72). This gave me an elevation of present-day ELA at 2000±50 m a.s.l.…”

Section: Palaeo Temperature Reconstructionmentioning

confidence: 99%

“…Detailed glacial geomorphological mapping of the Ahuriri study site is presented in the previous chapter (Chapter 4) or in Tielidze et al (2021). This chapter only describes three distinct terminal and lateral (hummocky) moraine systems.…”

Section: B -Location Map Of Newmentioning

confidence: 99%

“…Multiple former shorelines (44°23'25''S, 169°39'31''E) at different elevations (~720-740 m a.s.l.) occur on the ice-margin contact slopes of the hummocky moraine belt which likely represents a palaeo lake and its subsequent recession (Tielidze et al, 2021). These shorelines manifest as multiple platforms nested at several elevations (~725, 734, and 740 m a.s.l.)…”

Section: Moraine Belt-3mentioning

confidence: 99%

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Late Quaternary glacier-climate reconstructions from the Southern Alps, New Zealand

Tielidze¹

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One of the outstanding problems in modern geoscience is identifying the cause of past climate changes, particularly the drivers of rapid climate change during Quaternary glacial cycles. Changes in the physical geography of Earth’s surface during the Late Quaternary are mainly dependent on glacial dynamics – periods of rapid warming produced significant amounts of meltwater that reshaped the landscape, changed global sea-level and influenced climate. Identifying the timing of key climate transitions during past warming episodes, such as the last glacial termination, may help to understand the future evolution of Earth’s climate system (e.g. Denton et al., 2021). In this thesis, using geomorphological mapping and sixty-six cosmogenic 10Be surface exposure ages obtained from ice sculpted bedrock surfaces and deposited moraine landforms, I constrain the local Last Glacial Maximum and subsequent timing of last glacial termination in the Ahuriri River valley, Southern Alps, New Zealand (44°15′S, 169°36′E). Using the maximum elevation of lateral moraine (MELM) and accumulation area ratio (AAR) methods, along with application of a temperature lapse rate, I estimate the equilibrium-line altitude (ELA) and associated temperatures from the same periods. The largest glacial event in the Ahuriri River valley occurred at 19.8±0.3 ka when the former Ahuriri Glacier reached its maximum extent, which coincides with the global Last Glacial Maximum. By 16.7±0.3 ka, ice had retreated ~18 km up-valley from the LGM position and deglaciation was accompanied by the formation of a shallow proglacial lake. Surface exposure ages from moraines situated in a tributary of the upper Ahuriri River valley indicate that a subsequent advance of the palaeo glacier culminated at 14.5±0.3 ka, while the next readvance or still stand occurred at 13.6±0.3 ka. About 1000 yr later (12.6±0.2 ka), the former glacier built another prominent terminal moraine ridge in the lower section of the upper right tributary valley. Reconstructions of past glacier geometries indicate that the local ELA was depressed by ~880 m and climate was 5±1 °C colder than present (1981–2010) at 19.8±0.3 ka, while ELA was depressed by ~770 m and climate was 4.4±0.9 °C colder at 16.7±0.3 ka. Subsequent estimations suggest ELA elevations at 14.5±0.3 ka, 13.6±0.3 ka, and 12.6±0.2 ka were ≤700 m, ≤630 m, and ~360 m lower than today. This equates to air temperatures of ≤3.9 °C, ≤3.5 °C, and 2.3±0.7 °C colder than today, assuming no changes in past precipitation. The results reported here provide the first dataset of Late Quaternary glacial maximum extent and deglaciation along with quantitative paleoclimate reconstructions from the Ahuriri River valley, Southern Alps, New Zealand. The small amount of warming estimated in this study between 19.8±0.3 and 16.7±0.3 ka differs somewhat from glacial reconstructions in other major valleys in the Southern Alps, specifically from Rakaia River valley (e.g. Putnam et al., 2013a) where a much larger amount of warming may have occurred during the same time. Robust constraints of glacier changes in the Ahuriri valley between 14.5±0.3 and 12.6±0.2 ka confirm that an early glacier readvance occurred in New Zealand at this time, which has been previously recognised with only limited evidence (e.g. Kaplan et al., 2010; Putnam et al., 2010a). The reconstructed ELA suggests that the coldest part of the Late Glacial reversal occurred at 14.5±0.3 ka. The new constraints from glacial records in the Ahuriri River valley presented in this study offer the opportunity to test hypotheses about the climate system, to better understand the processes that drove ice retreat and readvance during the Last Glacial Maximum and subsequent termination.

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Section: Locationmentioning

confidence: 99%

Section: Approach Used In This Thesismentioning

confidence: 99%

Section: Palaeo Temperature Reconstructionmentioning

confidence: 99%

Section: B -Location Map Of Newmentioning

confidence: 99%

Section: Moraine Belt-3mentioning

confidence: 99%

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Late Quaternary glacier-climate reconstructions from the Southern Alps, New Zealand

Tielidze¹

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Early glacier advance in New Zealand during the Antarctic Cold Reversal

Tielidze

Eaves

Norton

et al. 2023

J Quaternary Science

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Glacial landscapes preserve records of past climate change. Investigating the glacier–climate system over the Late Quaternary provides information about past climate change and context for present‐day glacier response to climate warming. Using 28 beryllium‐10 (10Be) surface exposure dates and snowline reconstructions, we present glacier fluctuations and climate changes for the Antarctic Cold Reversal in the Ahuriri River catchment, Southern Alps of New Zealand (44°7′50″S, 169°38′29″E). Prominent terminal and lateral moraine features from the upper right tributary of the Ahuriri River valley have exposure ages of 14.5 ± 0.3, 13.6 ± 0.3 and 12.6 ± 0.2 ka, suggesting retreat of the glacier during the Antarctic Cold Reversal. Maximum elevation of lateral moraines (MELM) and accumulation area ratio (AAR) suggest snowline elevations at these ages were ≤700, ≤630 and ~360 m lower than today, respectively. This equates to air temperatures ≤3.9, ≤3.5 and 2.3 ± 0.7 °C lower than today (1981–2010), assuming no changes in past precipitation. Ice‐sculpted bedrock surfaces bound by a lateral moraine at nearby Canyon Creek have an age of 13.1 ± 0.3 ka, indicating the moraine correlates with those in the Ahuriri upper right tributary. MELM and AAR reconstructions from the Canyon Creek suggest that snowline elevations at 14.5–13.6 ka were ≤500 or ~380 m lower than today, corresponding to air temperatures ≤2.8 or 2.4 ± 0.7 °C lower than the present‐day (1981–2010). Our results provide insight into the structure of the Antarctic Cold Reversal in the Southern Alps, showing that the largest glacier advance occurred at the start of this interval at c. 14.5 ± 0.3 ka and was followed by gradual retreat. We hypothesize that the early cooling and glacier readvance in New Zealand at the onset of the Antarctic Cold Reversal were triggered by a latitudinal shift of the Southern Hemisphere westerly wind belt.

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Late Quaternary of the southwest Pacific region

Eaves

2025

Encyclopedia of Quaternary Science

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Glacial geomorphology of the Ahuriri River valley, central Southern Alps, New Zealand

Cited by 7 publications

References 29 publications

Late Quaternary glacier-climate reconstructions from the Southern Alps, New Zealand

Late Quaternary glacier-climate reconstructions from the Southern Alps, New Zealand

Early glacier advance in New Zealand during the Antarctic Cold Reversal

Late Quaternary of the southwest Pacific region

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