scholarly journals Delayed and rapid deglaciation of alpine valleys in the Sawatch Range, southern Rocky Mountains, USA

Geochronology ◽  
2020 ◽  
Vol 2 (2) ◽  
pp. 245-255
Author(s):  
Joseph P. Tulenko ◽  
William Caffee ◽  
Avriel D. Schweinsberg ◽  
Jason P. Briner ◽  
Eric M. Leonard
Keyword(s):  
Last Glacial Maximum ◽  
North Atlantic ◽  
North American ◽  
Rocky Mountains ◽  
Ice Sheets ◽  
Glacial Maximum ◽  
Last Glacial ◽  
Southern Rocky Mountains ◽  
The North ◽  
Sawatch Range

Abstract. We quantify retreat rates for three alpine glaciers in the Sawatch Range of the southern Rocky Mountains following the Last Glacial Maximum using 10Be ages from ice-sculpted, valley-floor bedrock transects and statistical analysis via the BACON program in R. Glacier retreat in the Sawatch Range from at (100 %) or near (∼83 %) Last Glacial Maximum extents initiated between 16.0 and 15.6 ka and was complete by 14.2–13.7 ka at rates ranging between 35.6 and 6.8 m a−1. Deglaciation in the Sawatch Range commenced ∼2–3 kyr later than the onset of rising global CO2 and prior to rising temperatures observed in the North Atlantic region at the Heinrich Stadial 1–Bølling transition. However, deglaciation in the Sawatch Range approximately aligns with the timing of Great Basin pluvial lake lowering. Recent data–modeling comparison efforts highlight the influence of the large North American ice sheets on climate in the western United States, and we hypothesize that recession of the North American ice sheets may have influenced the timing and rate of deglaciation in the Sawatch Range. While we cannot definitively argue for exclusively North Atlantic forcing or North American ice sheet forcing, our data demonstrate the importance of regional forcing mechanisms for past climate records.

scholarly journals Delayed and rapid deglaciation of alpine valleys in the Sawatch Range, southern Rocky Mountains, USA

2020 ◽  
Author(s):  
Joseph P. Tulenko ◽  
William Caffee ◽  
Avriel D. Schweinsberg ◽  
Jason P. Briner ◽  
Eric M. Leonard
Keyword(s):  
Last Glacial Maximum ◽  
North Atlantic ◽  
North American ◽  
Rocky Mountains ◽  
Ice Sheets ◽  
Last Glacial ◽  
Southern Rocky Mountains ◽  
The North ◽  
The North Atlantic ◽  
Sawatch Range

Abstract. We quantify retreat rates for three alpine glaciers in the Sawatch Range of the southern Rocky Mountains following the Last Glacial Maximum using 10Be ages from ice-sculpted, valley-floor bedrock transects and statistical analysis via the BACON program in R. Glacier retreat in the Sawatch Range from at (100 %) or near (~ 83 %) Last Glacial Maximum extents initiated between 16.3 and 15.6 ka and was complete by 14.2–13.7 ka at rates ranging between 9.9 and 19.8 m a−1. Deglaciation in the Sawatch Range commenced ~ 2–3 kyr later than the onset of rising global CO2, but approximately in-step with rising temperatures observed in the North Atlantic region at the Heinrich Stadial 1/Bølling transition. Our results highlight a possible teleconnection between the North Atlantic sector and the southern Rocky Mountains. However, deglaciation in the Sawatch Range also approximately aligns with the timing of Great Basin pluvial lake lowering. Recent data-modeling comparison efforts highlight the influence of the large North American ice sheets on climate in the western United States, and we hypothesize that recession of the North American ice sheets may have influenced the timing and rate of deglaciation in the Sawatch Range. While we cannot definitively argue for exclusively North Atlantic forcing or North American ice sheet forcing, our data demonstrate the importance of regional forcing mechanisms on past climate records.

scholarly journals Deglaciation of the Colorado Rocky Mountains following the Last Glacial Maximum

2017 ◽  
Vol 43 (2) ◽  
pp. 497 ◽  
Author(s):  
E.M. Leonard ◽  
B.J.B. Laabs ◽  
A.D. Schweinsberg ◽  
C.M. Russell ◽  
J.P. Briner ◽  
...  
Keyword(s):  
Last Glacial Maximum ◽  
Rocky Mountains ◽  
Glacial Maximum ◽  
San Juan ◽  
The South ◽  
Last Glacial ◽  
San Juan Mountains ◽  
The North ◽  
Colorado Rocky Mountains ◽  
Exposure Ages

The availability of almost 180 cosmogenic-radionuclide (CRN) surface-exposure ages from moraine boulders and glacially polished bedrock surfaces makes possible an assessment of the timing and character of the local Last Glacial Maximum (LLGM) and subsequent deglaciation in the Colorado Rocky Mountains. A review of glacial chronologies and numerical modeling results indicates that although glaciers across Colorado responded broadly synchronously, apparent differences in the timing and magnitude of glacier retreat following the LLGM suggest that spatially variable regional forcing, possibly precipitation related, played a role in glacier behavior along with more spatially uniform hemispheric or global forcing. Glaciers in the five ranges examined reached their greatest LLGM extents before ~19.5 ka and abandoned their outermost LLGM moraines between ~23.5 and 19.5 ka. Detailed deglaciation chronologies are available for glaciers in four of the ranges. In the Sawatch Range and Sangre de Cristo Mountains, glaciers were near their LLGM extents at 17-16 ka, before retreating rapidly. In the San Juan Mountains and the Front Range, glaciers may have begun their post-LLGM recession earlier, although early deglaciation is indicated by only a few ages on polished bedrock that potentially contains pre-LLGM CRN inheritance, and thus may be too old. Regardless of the timing of the onset of deglaciation, the equilibrium-line rise associated with deglaciation was earlier and significantly larger in the San Juan Mountains than elsewhere in Colorado. This suggests that the San Juan Mountains, located well to the southwest of the other ranges, may have experienced enhanced precipitation during the LLGM, as did areas farther to the south and west, while LLGM conditions may have been drier in the northern and eastern Colorado ranges. A breakdown in this pattern after the LLGM, with precipitation decreasing in the south and west and increasing in the north and east, may have led to the range-to-range differences evident across Colorado. Deglaciation was nearly complete in all four ranges by 15-13 ka. While some proxy records indicate a later Younger Dryas-age cooling in the Colorado mountains, there is not clear moraine evidence of glacier readvance at that time.

scholarly journals Extratropical cyclones over the North Atlantic and western Europe during the Last Glacial Maximum and implications for proxy interpretation

2020 ◽  
Vol 16 (2) ◽  
pp. 611-626 ◽  
Author(s):  
Joaquim G. Pinto ◽  
Patrick Ludwig
Keyword(s):  
Last Glacial Maximum ◽  
North Atlantic ◽  
Western Europe ◽  
Dust Storms ◽  
Glacial Maximum ◽  
Extratropical Cyclones ◽  
Last Glacial ◽  
The North ◽  
Dominant Feature ◽  
The North Atlantic

Abstract. Extratropical cyclones are a dominant feature of the midlatitudes, as their passage is associated with strong winds, precipitation and temperature changes. The statistics and characteristics of extratropical cyclones over the North Atlantic region exhibit some fundamental differences between pre-industrial (PI) and Last Glacial Maximum (LGM) climate conditions. Here, the statistics are analysed based on results of a tracking algorithm applied to global PI and LGM climate simulations. During the LGM, both the number and the intensity of detected cyclones were higher compared to PI. In particular, increased cyclone track activity is detected close to the Laurentide ice sheet and over central Europe. To determine changes in cyclone characteristics, the top 30 extreme storm events for PI and LGM have been simulated with a regional climate model and high resolution (12.5 km grid spacing) over the eastern North Atlantic and western Europe. Results show that LGM extreme cyclones were characterised by weaker precipitation, enhanced frontal temperature gradients and stronger wind speeds than PI analogues. These results are in line with the view of a colder and drier Europe, characterised by little vegetation and affected by frequent dust storms, leading to reallocation and build-up of thick loess deposits in Europe.

Air-sea coupling shapes North American hydroclimate response to ice sheets during the Last Glacial Maximum

2021 ◽  
pp. 117271
Author(s):  
Dillon J. Amaya ◽  
Alan M. Seltzer ◽  
Kristopher B. Karnauskas ◽  
Juan M. Lora ◽  
Xiyue Zhang ◽  
...  
Keyword(s):  
Last Glacial Maximum ◽  
North American ◽  
Ice Sheets ◽  
Glacial Maximum ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Last Glacial
Sign in / Sign up

Export Citation Format

Share Document