Cosmogenic nuclide surface-exposure dating (SED) is a rapidly growing tool in geoscience owing to its unrivalled potential for directly dating rock surfaces and thus the geomorphic and climatic events they represent. Fundamental to the efficacy of the SED method is reliable constraint of the in situ production rate, which is typically calculated via calibration experiments: cosmogenic nuclide concentrations are measured in surfaces for which the true exposure age is known independently, allowing the production rate to be derived (in atoms g-1 yr-1) for the specific calibration site. This value can then be extrapolated to distal field sites using numerical scaling methods designed to account for spatial and elevational differences in geomagnetic and atmospheric shielding. Thanks to successive and increasingly co-ordinated calibration efforts, production rate estimates for the most widely used cosmogenic nuclide, beryllium-10 (10Be), have improved in recent decades, with the majority converging on sea-level high-latitude (SLHL) values of similar to 3.8-4.1 atoms g-1 yr-1 ("St" scaling). Nonetheless, there remains sufficient variability among production rates to undermine the reliability of derived surface-exposure ages, particularly for applications to short-lived events such as the abrupt climate shifts of the last glacial termination. To help address this uncertainty, this paper reports new 10Be concentrations from deglacial surfaces on the Redpoint Peninsula in north-west Scotland that were exposed during retreat of the last British ice sheet. By comparing the surface-exposure results from eight current 10Be production rates to local radiocarbon constraint for deglaciation, we (1) evaluate the viability of each production rate for this site and (2) report a maximum SLHL value of 3.925 +/- 0.07 atoms g-1 yr-1 ("St" scaling), above which resulting surface-exposure ages will be too young with respect to the Redpoint radiocarbon chronology. This study also demonstrates that the Rannoch Moor 10Be production rate, calibrated against independently dated glacial landforms in the central Scottish Highlands, gives the best match with the 14C control and thus is appropriate for Late Pleistocene applications at these geomagnetic latitudes.

Determining whether both hemispheres warmed synchronously during the last deglaciation is important for identifying mechanisms for ice-age terminations. Here, we show that intermediate waters in the southwestern Pacific Ocean warmed simultaneously with some of the upper ocean waters in the Atlantic during Heinrich Stadial 1. In both regions, proxy records from benthic foraminifera show warming to interglacial temperatures beginning ~18,000 years ago and concluding by ~15,000 years ago. Our observations require a mechanism capable of producing rapid warming in these nearly antipodal ocean basins. We propose that some of the oceanic warming signal co-registered between these sites can be explained by a shift of the Southern Hemisphere Westerly Winds, which increased the temperature of intermediate water masses produced in the Southern Ocean. Taken together with results from Earth-system modeling experiments, we suggest that the Southern Hemisphere climate system played a role in regulating interhemispheric oceanic heat transport at millennial timescales. Intermediate waters in the southwestern Pacific Ocean warmed simultaneously with upper ocean waters in the Atlantic during Heinrich Stadial 1, possibly due to a southward shift of the Southern Hemisphere Westerly Winds, according to analyses of benthic foraminifera proxy records

Hydroclimatic change in the Asian interior plays a key role in regulating regional environmental sustainability, water security, and human-nature relationships. However, the influence of the summer monsoon and westerly circulation on the evolution of hydroclimate over the arid Asian interior remains controversial. Here we present newly collected hydroclimate proxies from loess in the Asian interior, together with transient model simulations, to address the coevolution of monsoon-induced extreme rainfall and significant westerly-affected drying during the mid-Holocene. Our results suggest that a drier mid-Holocene in the southern Tarim Basin was associated with a poleward displacement of the westerly jet due to relatively warm boreal summer temperatures in the mid-latitudes. Strengthened water vapor fluxes associated with the boreal summer monsoon facilitated extreme rainfall events and enhanced mountain erosion. Our proxy-model comparison reveals a drier westerly regime superimposed with strengthened rainfall over the Asian interior during the warm mid-Holocene. Our findings suggest that more summer flash rainstorm events are likely to occur in a warmer world, with enhanced drying in the hyper-arid Asian interior. Mid-Holocene dry climate in the Asian interior was associated with the poleward displacement of the westerly jet due to warm boreal summer temperatures at mid-latitudes, according to hydroclimate, radiocarbon and paleoclimate data and transient model simulations.

The last glacial termination featured a major reconfiguration of Earth's climate and cryosphere, whose underlying cause remains unresolved. To investigate this problem, we combine Be-10 surface-exposure dating of moraines with former equilibrium line altitudes to determine the magnitude and timing of atmospheric temperature warming that ended the Last Glaciation in the Takap & omacr;/Tekapo valley in the central Southern Alps of New Zealand. We show mountain-valley glacier recession from a nearly full-glacial configuration to a near-interglacial configuration early in the termination between similar to 18,000 and similar to 17,000 yrs ago, commensurate with a net atmospheric warming of similar to 3.8 degreesC (from -6.25 degreesC to -2.5 degreesC cooler than present). Similar recession also affected mid-latitude mountain glaciers in South America. We suggest trans-South Pacific glacier withdrawal early in the termination resulted from a decisive poleward shift of the austral westerlies that increased the proportion of warm subtropical air masses flowing over southern mid-latitude mountains, markedly raising glacier ablation rates. Farther south, the poleward-shifted westerlies drove increased ocean upwelling and surface warming, outgassing of carbon dioxide, and progressive ocean destratification, together raising atmospheric temperature over the Antarctic Ice Sheet, but at a rate slower than over mid-latitude mountain glaciers. Overall, we consider that Southern Hemisphere middle-latitude glacier recession was linked to Antarctic warming by a poleward displacement in latitude and an increase in strength of the Southern Hemisphere westerlies.

AbstractPremiseMany plant communities across the world are undergoing changes due to climate change, human disturbance, and other threats. These community‐level changes are often tracked with the use of permanent vegetative plots, but this approach is not always feasible. As an alternative, we propose using photogrammetry, specifically photograph‐based digital surface models (DSMs) developed using structure‐from‐motion, to establish virtual permanent plots in plant communities where the use of permanent structures may not be possible.MethodsIn 2021 and 2022, we took iPhone photographs to record species presence in 1‐m2 plots distributed across alpine communities in the northeastern United States. We then compared field estimates of percent coverage with coverage estimated using DSMs.ResultsDigital surface models can provide effective, minimally invasive, and permanent records of plant species presence and percent coverage, while also allowing managers to mark survey locations virtually for long‐term monitoring. We found that percent coverage estimated from DSMs did not differ from field estimates for most species and substrates.DiscussionIn order to continue surveying efforts in areas where permanent structures or other surveying methods are not feasible, photogrammetry and structure‐from‐motion methods can provide a low‐cost approach that allows agencies to accurately survey and record sensitive plant communities through time.

From 10Be surface-exposure dating we make the case that classic late-glacial moraines in southwestern Norway, including the iconic Esmark moraine, and in the Southern Hemisphere middle latitudes, including the iconic Birch Hill moraine of the Southern Alps of New Zealand, were constructed coevally within dating uncertainties. This finding of simultaneous glacier resurgence in the two polar hemispheres carries the implication that the millennial-scale climate reversal of the last deglaciation was global and required a change in the energy budget of the earth's climate system.

Knowledge of microparticle geometry is essential for accurate calculation of ice core volume-related dust metrics (mass, flux, and particle size distributions) and subsequent paleoclimate interpretations, yet particle shape data remain sparse in Antarctica. Here we present 41 discrete particle shape measurements, volume calculations, and calibrated continuous particle time series spanning 50–16 ka from the South Pole Ice Core (SPC14) to assess particle shape characteristics and variability. We used FlowCAM, a dynamic particle imaging instrument, to measure aspect ratios (width divided by length) of microparticles. We then compared those results to Coulter counter measurements on the same set of samples as well as high-resolution laser-based (Abakus) data collected from SPC14 during continuous flow analysis. The 41 discrete samples were collected during three periods of millennial-scale climate variability: Heinrich Stadial 1 (18–16 ka, n=6; ∼250 years per sample), the Last Glacial Maximum (LGM) (27–18 ka, n=19; ∼460 years per sample), and during both Heinrich Stadial 4 (42–36 ka, n=8; ∼620 years per sample) and Heinrich Stadial 5 (50–46 ka, n=8; ∼440 years per sample). Using FlowCAM measurements, we calculated different particle size distributions (PSDs) for spherical and ellipsoidal volume estimates. Our calculated volumes were then compared to published Abakus calibration techniques. We found that Abakus-derived PSDs calculated assuming ellipsoidal, rather than spherical, particle shapes provide a more accurate representation of PSDs measured by Coulter counter, reducing Abakus to Coulter counter flux and mass ratios from 1.82 (spherical assumption) to 0.79 and 1.20 (ellipsoidal assumptions; 1 being a perfect match). Coarser particles (>5.0 µm diameter) show greater variation in measured aspect ratios than finer particles (<5.0 µm). While fine particle volumes can be accurately estimated using the spherical assumption, applying the same assumption to coarse particles has a large effect on inferred particle volumes. Temporally, coarse and fine particle aspect ratios do not significantly change within or among the three time periods (p value >0.05), suggesting that long-range transport of dust is likely dominated by clay minerals and other elongated minerals.

The accelerating flux of glacial meltwater to the oceans due to global warming is a potential trigger for future climate disturbance. Past disruption of Atlantic Ocean circulation, driven by melting of land‐based ice, is linked in models to reduced ocean‐atmosphere heat transfer and abrupt cooling during stadial events. The most recent stadial, the Younger Dryas (YD), is traditionally viewed as a severe cooling centered on the North Atlantic but with hemispheric influence. However, indications of summer warmth question whether YD cooling was truly year‐round or restricted to winter. Here, we present a beryllium‐10‐dated glacier record from the north‐east North Atlantic, coupled with 2‐D glacier‐climate modeling, to reconstruct Lateglacial summer air temperature patterns. Our record reveals that, contrary to the prevailing model, the last glacial advance in Scotland did not occur during the YD but predated the stadial, while the YD itself was characterized by warming‐driven deglaciation. We argue that these apparently paradoxical findings can be reconciled with regional and global climate events by invoking enhanced North Atlantic seasonality—with anomalously cold winters but warming summers—as an intrinsic response to globally increased poleward heat fluxes.

In regions of the globe at middle and high latitudes, glacial periods have waxed and waned for hundreds of millennia. Glacier-derived sediment in a Peruvian lake suggests that tropical glaciers have moved to a similar beat.

Mountain glaciers are highly sensitive to climate change. However, the extent to which glaciers capture regional to hemisphere‐scale atmospheric processes remains uncertain, hindering paleoclimatic interpretations derived from moraine‐based glacier reconstructions. Here, we evaluate how mid‐latitude glacier systems monitor climate by comparing climate reanalysis products with glacier annual equilibrium line altitude (ELA) elevations from the antipodal Southern Alps of New Zealand and European Alps. We find significant regional and hemispheric correlations between glacier annual ELA and summer tropospheric temperatures. Annual ELA also exhibit positive correlations with the latitude of the westerly jets in both hemispheres. These results indicate that westerly wind‐belt latitude modulates the proportion of cold versus warm air masses influencing these glacier systems. These results highlight the sensitivity of mid‐latitude glaciers to atmospheric temperatures and circulation, with implications for interpreting moraine‐based paleoclimate reconstructions. Combined impacts of ongoing tropospheric warming and poleward‐shifting westerlies will likely accelerate recession of mid‐latitude glaciers.

Determining what caused the global Last Glaciation and last glacial termination, despite opposing orbital summer insolation signatures between the polar hemispheres, remains a puzzle of paleoclimatology. This problem can be addressed by comparing chronologies of glaciation from different latitudes and different climatic regimes in both hemispheres. Here, we present a 10 Be surface‐exposure chronology of glacial landforms constructed during and since the local Last Glaciation in the continental environment of Central Asia in the high Mongolian Altai (49°N, 88°E). Four belts of lateral moraines document maximal phases of the former Khoton glacier at 35,440 ± 980 years ago, 23,430 ± 850 years ago, 20,780 ± 610 years ago, and 19,520 ± 550 years ago. Our chronology indicates that deglaciation from these maximal positions began as early as 18,810 ± 510 years ago, was well underway by 17,680 ± 510 years ago, and was nearly completed by 16,040 ± 490 years ago. Overall, our chronology shows that glaciation in western Mongolia overlapped with the global Last Glacial Maximum and that extensive recession from glacial‐to‐interglacial limits took place early in the last glacial termination during Heinrich Stadial 1. Khoton Nuur deglaciation led the demise of large Northern Hemisphere ice sheets and increases in radiative forcing agents by several millennia. We suggest that this rapid switch in the mode of glaciation implies the involvement of an additional climatic factor that could have produced locally rapid warming and deglaciation ∼18,800–16,000 years ago.

Millennial-scale climate oscillations of the last ice age registered in Greenland and Antarctic ice cores did not always vary in unison. A striking example is that the strongest Antarctic warming episodes occurred during Heinrich episodes in the North Atlantic region. Although the bipolar seesaw affords a possible explanation for such anti-phasing, it does not account for the equally striking observation that climate varied in unison between the hemispheres about half the time. Such phasing differences suggest the need for an alternative hypothesis in which the polar regions at times responded in unison to common forcing, and at other times left the impression of a bipolar seesaw. We posit that this impression arose from the effect of warmer-than-usual summers on continental ice sheets adjacent to the North Atlantic Ocean during each Heinrich episode. The relatively warm Heinrich summers produced discharges of meltwater and icebergs of sufficient volume to stimulate very cold winter conditions from widespread sea ice on a freshened ocean surface. The intervals between Heinrich episodes featured relaxation of sea-ice-induced winter severity from reduced summertime influx of meltwater and icebergs, indicating relatively cooler summer conditions. It is postulated that the causative variations in freshwater fluxes were driven by a climate signal most evident in Antarctic ice cores but also recognized in other paleoclimate records in both polar hemispheres. We suggest that this widespread signal arose from changes in the latitude and strength of the austral westerlies and the resulting effect on the western Pacific tropical warm pool, a mechanism dubbed the Zealandia Switch.

Two fundamental questions about the ice-age climate system await satisfactory resolution. First, if summer solar radiation intensity truly controls the orbital signature of the last glacial cycle, then why were major climatic shifts, including the last termination, globally synchronous? Second, what caused the millennial-scale climate oscillations superimposed on this cycle? We address these questions from a Southern Hemisphere perspective focused on mid-latitude mountain ice fields. We put particular emphasis on the last glacial termination, which involved both orbital-scale and millennial-scale climate elements and has generally well-resolved chronological control. Sustained retreat of mountain glaciers, documented by detailed mapping and chronology of glacial landforms in the Southern Alps and southern Andes, marked the termination of the last ice age, beginning similar to 18 kyrs ago and involved a change from glacial to near-interglacial atmospheric temperature within a millennium or two. A rapid poleward shift of the Subtropical Front, delineating the northern margin of the Southern Ocean, similar to 18 kyrs ago implies a concurrent poleward shift of the austral westerlies and leads us to hypothesize a southern origin for the dominant phase of the last glacial termination. Together with interhemispheric paleoclimate records and with results of coupled ocean-atmosphere climate modeling, these findings suggest a big, fast, and global end to the last ice age in which a southern-sourced warming episode linked the hemispheres. We posit that a shift in the Southern Ocean circulation and austral westerly wind system, tied to southern orbital forcing, caused this global warming episode by affecting the tropical heat engine and hence global climate. Central to this hypothesis, dubbed the 'Zealandia Switch', is the location of the Australia and Zealandia continents relative to Southern Hemisphere oceanic and atmospheric circulation. Coupled ocean-atmosphere climate modeling shows that the locus of the austral westerlies, whether in a more equatorward position representing a glacial-mode climate or in a poleward-shifted position marking interglacial-mode climate, has profound effects on oceanic and associated atmospheric linkages between the tropical Pacific and the Southern Ocean. Shifts in the austral westerlies have global climatic consequences, especially through resulting changes in the greenhouse gas content of the atmosphere and altered heat flux from the tropical Pacific into the Northern and Southern Hemispheres. We suggest that the last glacial termination was a global warming episode that led to extreme seasonality in northern latitudes by stimulating a flush of meltwater and icebergs into the North Atlantic from adjoining ice sheets. This fresh-water influx resulted in widespread North Atlantic sea ice that caused very cold boreal winters, thus amplifying the annual southward shift of the Intertropical Convergence Zone and the monsoonal rain belts. We further suggest that muted manifestations of the Zealandia Switch mechanism were responsible for smaller, recurring millennial-scale climate oscillations within the last glacial cycle. (C) 2020 Elsevier Ltd. All rights reserved.

ABSTRACT Shorelines formed by terminal lakes record past changes in regional moisture budgets. In the western Great Basin of North America, winter precipitation accounts for nearly half of the annual total and is well correlated with northeast Pacific storm track activity and moisture transport. We evaluated these relationships and found that historical precipitation between 1910 and 2012 was better correlated to moisture transport (0.78, p < 0.01) than to storm track activity (0.54, p < 0.01) because moisture transport better captures dynamics associated with the Sierra Nevada rain shadow. We derived modern analogs of enhanced and reduced storm track activity and moisture transport from reanalysis products and used associated winter precipitation anomalies with these analogs as inputs to a coupled water balance and lake evaporation model of the Walker Lake basin. Simulated lake-level responses were compared with a radiocarbon-dated lakeshore chronology spanning the past 3700 yr. Wet analogs developed from winters in the 90th and 75th percentiles for storminess and moisture transport produced lake levels that exceeded estimated late Holocene highstands by 50 m. Dry analogs (10th and 25th percentiles) produced lake levels corresponding to Medieval megadrought lowstands. The twentieth century is shown to be as wet as any century in the past 3700 yr. Our results demonstrate the sensitivity of terminal lakes to winter season circulations and highlight the value of using moisture transport as a predictor of cool season precipitation and to evaluate how past or future changes in regional circulations will influence the water balance of dryland regions.

Debates on addressing climate change focus on the need to replacing fossil fuels with renewable energy. This paper reviews roles of different renewable energy technologies in adaptation and mitigation of climate change in Nepal. The potential and capacity of different energies are high in Nepal, but it has not been able to harness. However, use of fossil fuels and conventional energy are still prevalent other renewable energies have been generated that has positively impacted social, economic, and environmental sectors in Nepal. Renewable Energy in Nepal: The use of renewable energy technologies (RETs) has enhanced climate change adaptation and mitigation in Nepal, a nation quite vulnerable to climate change. Solar energy, hydroelectricity plants, biogas, improved cooking stoves (ICS), and wind energy systems are being popular every year. However, the consumption of fossil fuels and conventional biomass energy is widely practiced in Nepal with adverse impacts on socioeconomic, health, and environmental sectors. Biomass and petroleum fuel account for 80% and 12% of the total energy while 3% energy is generated from grid electricity and RETs (Fig. 1). Households consume the highest energy (43%) followed by industrial sector (38%). Fig. 1. Generation by different sources (GoN, 2015) Indoor air pollution causing eye and respiratory diseases resulting mortality of more than 7500 women and children is the impact of using conventional biomass (fuelwood, cattle dung, agricultural residue), and kerosene for cooking at household level. Traditional biomass and imported non-renewable energy are responsible for Greenhouse Gas (GHG) emissions in Nepal. Hydro power is popular in Nepal due to perpetual flowing rivers (approx. 6000) having current capacity of 967.85 Mw. Nepal has 300 days of sun a year, receiving 3.6-6.2 kWh of solar radiation with potential of 2100 Mw (Table. 1). Wind energy accounts for 113.6 kW capacity. Table 1. Potential of RETs (Paudyal et al., 2019). S.N. RETs Potentiality 1 Mini/Micro hydro >100 MW 2 Solar energy 2100 MW 3 Improved water mill 25-30,000 MW 4 Wind energy 3000 MW Construction of RETs at local level has reduced dependency on forest products reducing emissions and enhancing carbon sequestration. RETs have been shown to promote health services, support quality education and social networks, create jobs, and earn revenue from clean development mechanisms. Acknowledgements: Dr. Katherine Glover, Dr. Cindy Isenhour, and Dr. Suraj Upadhaya Bibliography: Government of Nepal. Ministry of finance. Nepal: Economic Survey. Kathmandu; 2015. Poudyal, Ramhari, Pavel Loskot, Rabindra Nepal, Ranjan Parajuli, and Shree Krishna Khadka. "Mitigating the current energy crisis in Nepal with renewable energy sources." Renewable and Sustainable Energy Reviews 116 (2019): 109388. 78% 12% 4% 3% 3% 6%