scholarly journals Rapid shifts in South American montane climates driven by <i>p</i>CO<sub>2</sub> and ice volume changes over the last two glacial cycles

2010 ◽  
Vol 6 (5) ◽  
pp. 2117-2158 ◽  
Author(s):  
M. H. M. Groot ◽  
R. G. Bogotá ◽  
L. J. Lourens ◽  
H. Hooghiemstra ◽  
M. Vriend ◽  
...  
Keyword(s):  
Ice Cores ◽  
Mean Annual Temperature ◽  
Climate Modelling ◽  
Pollen Record ◽  
South American ◽  
Glacial Cycles ◽  
Migration Patterns ◽  
Greenhouse Gasses ◽  
Ice Volume ◽  
Lapse Rates

Abstract. Tropical montane biome migration patterns in the northern Andes are found to be coupled to glacial-induced mean annual temperature (MAT) changes; however, the accuracy and resolution of current records are insufficient to fully explore their magnitude and rates of change. Here we present a ~60-year resolution pollen record over the past 284 000 years from Lake Fúquene (5° N) in Colombia. This record shows rapid and extreme MAT changes at 2540 m elevation of up to 10 ± 2 °C within a few hundred of years that concur with the ~100 and 41-kyr (obliquity) paced glacial cycles and North Atlantic abrupt climatic events as documented in ice cores and marine sediments. Using transient climate modelling experiments we demonstrate that insolation-controlled ice volume and greenhouse gasses are the major forcing agents causing the orbital MAT changes, but that the model simulations significantly underestimate changes in lapse rates and local hydrology and vegetation feedbacks within the studied region due to its low spatial resolution.

scholarly journals Ultra-high resolution pollen record from the northern Andes reveals rapid shifts in montane climates within the last two glacial cycles

2011 ◽  
Vol 7 (1) ◽  
pp. 299-316 ◽  
Author(s):  
M. H. M. Groot ◽  
R. G. Bogotá ◽  
L. J. Lourens ◽  
H. Hooghiemstra ◽  
M. Vriend ◽  
...  
Keyword(s):  
Mean Annual Temperature ◽  
High Mountain ◽  
Climate Modelling ◽  
Pollen Record ◽  
Glacial Cycles ◽  
Greenhouse Gasses ◽  
Ice Volume ◽  
Arboreal Pollen ◽  
Age Model ◽  
Mountain Vegetation

Abstract. Here we developed a composite pollen-based record of altitudinal vegetation changes from Lake Fúquene (5° N) in Colombia at 2540 m elevation. We quantitatively calibrated Arboreal Pollen percentages (AP%) into mean annual temperature (MAT) changes with an unprecedented ~60-year resolution over the past 284 000 years. An age model for the AP% record was constructed using frequency analysis in the depth domain and tuning of the distinct obliquity-related variations to the latest marine oxygen isotope stacked record. The reconstructed MAT record largely concurs with the ~100 and 41-kyr (obliquity) paced glacial cycles and is superimposed by extreme changes of up to 7 to 10° Celsius within a few hundred years at the major glacial terminations and during marine isotope stage 3, suggesting an unprecedented North Atlantic – equatorial link. Using intermediate complexity transient climate modelling experiments, we demonstrate that ice volume and greenhouse gasses are the major forcing agents causing the orbital-related MAT changes, while direct precession-induced insolation changes had no significant impact on the high mountain vegetation during the last two glacial cycles.

scholarly journals Global glacier dynamics during 100 ka Pleistocene glacial cycles

2018 ◽  
Vol 90 (1) ◽  
pp. 222-243 ◽  
Author(s):  
Philip D. Hughes ◽  
Philip L. Gibbard
Keyword(s):  
Solar Radiation ◽  
Global Climate ◽  
Ice Cores ◽  
External Control ◽  
Glacial Cycles ◽  
Mountain Glaciers ◽  
Ice Volume ◽  
Double Peaks ◽  
Dust Flux ◽  
Solar Radiation Flux

AbstractIce volume during the last ten 100 ka glacial cycles was driven by solar radiation flux in the Northern Hemisphere. Early minima in solar radiation combined with critical levels of atmospheric CO2drove initial glacier expansion. Glacial cycles between Marine Isotope Stage (MIS) 24 and MIS 13, whilst at 100 ka periodicity, were irregular in amplitude, and the shift to the largest amplitude 100 ka glacial cycles occurred after MIS 16. Mountain glaciers in the mid-latitudes and Asia reached their maximum extents early in glacial cycles, then retreated as global climate became increasingly arid. In contrast, larger ice masses close to maritime moisture sources continued to build up and dominated global glacial maxima reflected in marine isotope and sea-level records. The effect of this pattern of glaciation on the state of the global atmosphere is evident in dust records from Antarctic ice cores, where pronounced double peaks in dust flux occur in all of the last eight glacial cycles. Glacier growth is strongly modulated by variations in solar radiation, especially in glacial inceptions. This external control accounts for ~50–60% of ice volume change through glacial cycles. Internal global glacier–climate dynamics account for the rest of the change, which is controlled by the geographic distributions of glaciers.

scholarly journals Borehole temperatures reveal details of 20th century warming at Bruce Plateau, Antarctic Peninsula

2012 ◽  
Vol 6 (3) ◽  
pp. 675-686 ◽  
Author(s):  
V. Zagorodnov ◽  
O. Nagornov ◽  
T. A. Scambos ◽  
A. Muto ◽  
E. Mosley-Thompson ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Antarctic Peninsula ◽  
Accumulation Rate ◽  
Ice Cores ◽  
Temperature History ◽  
Mean Annual Temperature ◽  
Measured Temperature ◽  
Climate Trends ◽  
Cold Temperatures ◽  
Reconstructed Surface

Abstract. Two ice core boreholes of 143.18 m and 447.73 m (bedrock) were drilled during the 2009–2010 austral summer on the Bruce Plateau at a location named LARISSA Site Beta (66°02' S, 64°04' W, 1975.5 m a.s.l.). Both boreholes were logged with thermistors shortly after drilling. The shallow borehole was instrumented for 4 months with a series of resistance thermometers with satellite uplink. Surface temperature proxy data derived from an inversion of the borehole temperature profiles are compared to available multi-decadal records from weather stations and ice cores located along a latitudinal transect of the Antarctic Peninsula to West Antarctica. The LARISSA Site Beta profiles show temperatures decreasing from the surface downward through the upper third of the ice, and warming thereafter to the bed. The average temperature for the most recent year is −14.78°C (measured at 15 m depth, abbreviated T15). A minimum temperature of −15.8°C is measured at 173 m depth, and basal temperature is estimated to be −10.2°C. Current mean annual temperature and the gradient in the lower part of the measured temperature profile have a best fit with an accumulation rate of 1.9×103 kg m−2 a−1 and basal heat flux (q) of 88 mW m−2, if steady-state conditions are assumed. However, the mid-level temperature variations show that recent temperature has varied significantly. Reconstructed surface temperatures (Ts=T15) over the last 200 yr are derived by an inversion technique (Tikhonov and Samarskii, 1990). From this, we find that cold temperatures (minimum Ts=−16.2°C) prevailed from ~1920 to ~1940, followed by a gradual rise of temperature to −14.2°C around 1995, then cooling over the following decade and warming in the last few years. The coldest period was preceded by a relatively warm 19th century at T15≥−15°C. To facilitate regional comparisons of the surface temperature history, we use our T15 data and nearby weather station records to refine estimates of lapse rates (altitudinal, adjusted for latitude: Γa(l)). Good temporal and spatial consistency of Γa(l) over the last 35 yr are observed, implying that the climate trends observed here are regional and consistent over a broad altitude range.

scholarly journals Basal temperature conditions of the Greenland ice sheet during the glacial cycles

1996 ◽  
Vol 23 ◽  
pp. 226-236 ◽  
Author(s):  
Philippe Huybrechts
Keyword(s):  
Steady State ◽  
Three Dimensional ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Ice Cores ◽  
Ice Thickness ◽  
Glacial Cycle ◽  
Glacial Cycles ◽  
Temperature Conditions ◽  
Strongly Damped

A high-resolution, three-dimensional thermomechanical ice-sheet model, which includes isostasy, the possibility of ice-sheet expansion on the continental shelf and refined climatic parameterizations, was used to investigate the basal thermal regime of the Greenland ice sheet. The thermodynamic calculations take into account the usual terms of heat flow within the ice, a thermally active bedrock layer and all of the effects associated with changes in ice thickness and flow pattern. Basal temperature conditions are documented with respect to glacial–interracial shifts in climatic boundary conditions, both in steady state as during simulations over the last two glacial cycles using the GRIP δ180 record. It is found that the basal temperature field shows a large sensitivity in steady-state experiments but that, during a glacial cycle, basal temperature variations are strongly damped, in particular in central areas. A comparison has been made with measured data from deep ice cores and the implications are discussed.

scholarly journals Glaciological studies at Siple Station (Antarctica): potential ice-core paleoclimatic record

1991 ◽  
Vol 37 (125) ◽  
pp. 11-22 ◽  
Author(s):  
E. Mosley-Thompson ◽  
J. Dai ◽  
L. G. Thompson ◽  
P. M. Grootes ◽  
James K. Arbogast ◽  
...  
Keyword(s):  
Seasonal Variations ◽  
Stratospheric Ozone ◽  
Ice Core ◽  
Spatial Coherence ◽  
Ice Cores ◽  
Mean Annual Temperature ◽  
Western Coast ◽  
Paleoenvironmental Reconstruction ◽  
High Accumulation ◽  
Oxygen Isotopic

Abstract The quality and utility of the records of oxygen-isotopic abundances, dust concentrations and anionic concentrations preserved in the ice at Siple Station (75°55′ S, 84° 15′ W) are assessed from four shallow (20 m) cores. The combination of high accumulation (0.56 m a−1 w.e.) and low mean annual temperature (—24°C) preserves the prominent seasonal variations in δ18Ο which are very spatially coherent. Sulfate concentrations vary seasonally and, in conjunction with δ18Ο, will allow accurate dating of deeper cores from Siple Station. The concentrations of insoluble dust are the lowest measured in Antarctica, making Siple Station an excellent location to examine large increases in atmospheric tubidity. The seasonal variations and annual fluxes of the anions are examined for the last two decades (AD 1966–85) with regard to probable sources. An unusually high sulfate flux in 1976 may reflect the February 1975 eruption of Mount Ngauruhoe, New Zealand. No annual signal in nitrate concentration is confirmed and no unusually high nitrate fluxes support the suggestion of nitrate production by large solar flares. However, nitrate flux is higher for the latter half of the 1970s and early 1980s, possibly reflecting the recent loss of stratospheric ozone. Finally, comparison of the δ18O record with available surface-temperature data (AD 1957–85) reveals that multi-year trends along the western coast of the Antarctic Peninsula are recorded at Siple. More importantly, comparison with areally weighted temperature reconstructions suggests that the δ18Ο record may reflect larger-scale, persistent trends in the high southern latitudes. The strong spatial coherence of the preserved records, the potential for accurate dating, and possible relevance to larger-scale processes make Siple Station an excellent site for paleoenvironmental reconstruction from ice cores.

On the astronomical forcing of simple conceptual ice age models

2020 ◽  
Author(s):  
Gaëlle Leloup ◽  
Didier Paillard
Keyword(s):  
Conceptual Model ◽  
Climate Model ◽  
Ice Age ◽  
Early Pleistocene ◽  
Model Parameters ◽  
Ice Ages ◽  
Glacial Cycles ◽  
Orbital Parameters ◽  
Ice Volume ◽  
Astronomical Forcing

&lt;p&gt;Variations of the Earth&amp;#8217;s orbital parameters are known to pace the ice volume variations of the last million year [1], even if the precise mechanisms remain unknown.&lt;br&gt;Several conceptual models have been used to try to better understand the connection between ice-sheet changes and the astronomical forcing. An often overlooked question is to decide which astronomical forcing can best explain the observed cycles.&lt;/p&gt;&lt;p&gt;A rather traditional practice was to use the insolation at a some specific day of the year, for instance at mid-july [2] or at the june solstice [3].&lt;br&gt;But it was also suggested that the integrated forcing above some given threshold could be a better alternative [4]. In a more recent paper, Tzedakis et al. [5] have shown that simple rules, based on the original Milankovitch forcing or caloric seasons, could also be used to explain the timing of ice ages.&lt;br&gt;Here we adapt and simplify the conceptual model of Parrenin and Paillard 2003 [6], to first reduce the set of parameters.&lt;br&gt;Like in the original conceptual model from [6], this simplified conceptual model is based on climate oscillations between two states: glaciation and deglaciation. It switches to one another when crossing a defined threshold. While the triggering of glaciations is only triggered by orbital parameters, the triggering of deglaciations is triggered by a combination of orbital parameters and ice volume. &lt;br&gt;Then, we apply the different possible forcings listed above and we try to adapt the model parameters to reproduce the ice volume record, at least in a qualitative way. This allows us to discuss which kind of astronomical forcing better explains the Quaternary ice ages, in the context of such simple threshold-based models.&lt;/p&gt;&lt;p&gt;[1] Variations in the Earth's Orbit: Pacemaker of the Ice Ages, Hays et al., 1976, Science&amp;#8232;&lt;/p&gt;&lt;p&gt;[2] Modeling the Climatic Response to Orbital Variations, Imbrie and Imbrie, 1980, Science&amp;#8232;&lt;/p&gt;&lt;p&gt;[3] The timing of Pleistocene glaciations from a simple multiple-state climate model, Paillard, 1998, Nature&lt;/p&gt;&lt;p&gt;[4] Early Pleistocene Glacial Cycles and the Integrated Summer Insolation Forcing, Huybers et al., 2006, Science&lt;/p&gt;&lt;p&gt;[5] A simple rule to determine which insolation cycles lead to interglacials, Tzedakis et al., 2017, Nature&lt;/p&gt;&lt;p&gt;[6] Amplitude and phase of glacial cycles from a conceptual model, Parrenin Paillard, 2003, EPSL.&lt;/p&gt;

Unraveling South American spatial precipitation patterns, intensity and variability through a multi-proxy approach for the past 2 kyr

2020 ◽  
Author(s):  
Francisco J. Briceño-Zuluaga ◽  
Juliana Nogueira ◽  
Heitor Evangelista ◽  
James Apaéstegui ◽  
Abdelfettah Sifeddine ◽  
...  
Keyword(s):  
South America ◽  
Hydrological Cycle ◽  
Climatic Variability ◽  
Ice Cores ◽  
High Standard ◽  
Water Vapor Transport ◽  
South American ◽  
Equatorial Atlantic ◽  
The South ◽  
Mountainous Regions

&lt;p&gt;South America hydrological cycle is highly dependent on the water vapor transport advected from tropical-equatorial Atlantic, Southern Pacific as well as the polar advections. While the Pacific contribution in the continental water budget is basically restricted to the western Andes region, the Atlantic Ocean and others mechanism &amp;#8211; as advection in Amazonas basin &amp;#8211; play a great role in modulating precipitation over the continent. Besides, modes of climatic variability, such as ENSO, have an important role in pluviosity distribution patterns and respectively intensity, influencing the availability of water resources from mountainous regions, vital to ecosystems and to economy and human wellbeing. Intense droughts and floods observed continentally during the modern epoch have pointed to the need of better understanding the regional climate related issue. Recent paleoclimate advances, especially the creation of high-standard regional proxy record databases, allow describing the South American climate from a new perspective. Here we present an effort of the South American PAGES 2k paleo-community LOTRED-SA to build a South America hydrology robust and unique multiproxy database. We present a spatial and temporal approach of the South American hydro-climate reconstruction based on more than 360 available databases in an attempt to unravel their changes and impacts. Following a multi-proxy approach, we expect to better describe duration and location of wet and dryer climate regimes at most important climate spatial domains, and modes patterns on South America, during each period; as well as their predominant variability base on high resolution records (tree rings, speleothems, lake, marine and ice cores). we combine here the use of different proxy records and spatial-temporal approach, owing to consolidate interpretations of the hydrological cycles in South America.&lt;/p&gt;

A Simple Model for Glacial Cycles and Impact of fossil fuel CO2 emissions

2020 ◽  
Author(s):  
Stefanie Talento ◽  
Andrey Ganopolski
Keyword(s):  
Fossil Fuel ◽  
Climate System ◽  
Total Carbon ◽  
Anthropogenic Emissions ◽  
Orbital Forcing ◽  
Glacial Cycles ◽  
Ice Volume ◽  
Global Mean Temperature ◽  
Physically Based ◽  
Linear Differential

&lt;p&gt;We propose a simple physically-based model of the coupled evolution of Northern Hemisphere (NH) landmass ice-volume, atmospheric CO&lt;sub&gt;2&lt;/sub&gt; concentration and global mean temperature. The model only external forcings are the orbital forcing (maximum solar insolation at 65&amp;#176;N) and anthropogenic CO&lt;sub&gt;2&lt;/sub&gt; emissions. The model consist of a system of 3 coupled non-linear differential equations, representing physical mechanisms relevant for the evolution of the climate system in time-scales longer than thousands of years.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;When forced by the orbital forcing only, the model is successful in reproducing the natural glacial-interglacial cycles of the last 800kyr, in agreement with paleorecords and simulations performed with the CLIMBER-2 Earth System Model of intermediate complexity. The model is successful in reproducing both the timing and amplitude of the glacial-interglacial variations, producing a correlation with paleodata of 0.75 in terms of NH ice-volume.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;For the next million years, we analyse the model results under different scenarios: the natural scenario (in which only orbital forcing is applied) and scenarios in which various magnitudes of fossil fuel CO&lt;sub&gt;2&lt;/sub&gt; emissions are considered (in addition to the orbital forcing).&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;When anthropogenic emissions are included the model shows that even fairly low CO&lt;sub&gt;2&lt;/sub&gt; anthropogenic emissions (100 Pg or larger) are capable of affecting the next glacial inception, expected to occur in 120kyr from now, delaying large NH ice formation by 50kyr. Considering total carbon releases ranging between 1000 and 5000 Pg (a reasonable expectation of fossil fuel CO&lt;sub&gt;2&lt;/sub&gt; emissions to occur in the next few hundred years) the temporal evolution of the climate system could be significantly different from the natural progression. Emissions larger than 3000 Pg could have long-lasting effects, being natural conditions not resumed even after 1 Million years have passed. In addition, emissions larger than 4000 Pg prevent glacial cycles in the next half million years.&lt;/p&gt;

Evaluation of Temperature Differences for Paired Stations of the U.S. Climate Reference Network

2005 ◽  
Vol 18 (10) ◽  
pp. 1629-1636 ◽  
Author(s):  
Kevin P. Gallo
Keyword(s):  
Reference Network ◽  
Mean Annual Temperature ◽  
Rural Settings ◽  
The Mean ◽  
Lapse Rates ◽  
The U.S

Abstract Adjustments to data observed at pairs of climate stations have been recommended to remove the biases introduced by differences between the stations in time of observation, temperature instrumentation, latitude, and elevation. A new network of climate stations, located in rural settings, permits comparisons of temperatures for several pairs of stations without two of the biases (time of observation and instrumentation). The daily, monthly, and annual minimum, maximum, and mean temperatures were compared for five pairs of stations included in the U.S. Climate Reference Network. Significant differences were found between the paired stations in the annual minimum, maximum, and mean temperatures for all five pairs of stations. Adjustments for latitude and elevation differences contributed to greater differences in mean annual temperature for four of the five stations. Lapse rates computed from the mean annual temperature differences between station pairs differed from a constant value, whether or not latitude adjustments were made to the data. The results suggest that microclimate influences on temperatures observed at nearby (horizontally and vertically) stations are potentially much greater than influences that might be due to latitude or elevation differences between the stations.

Abrupt Climatic Changes during the Last Glaciation Based on Pollen Analysis of the Abric Romani, Catalonia, Spain

1994 ◽  
Vol 42 (3) ◽  
pp. 308-315 ◽  
Author(s):  
Francesc Burjachs ◽  
Ramon Julià
Keyword(s):  
Ice Cores ◽  
Pollen Record ◽  
Humid Climate ◽  
Third Phase ◽  
Last Glaciation ◽  
Composition And Structure ◽  
Stage 4 ◽  
Cold Events ◽  
Abric Romaní ◽  
Frequency Variations

AbstractThe Abric Romani continental pollen record provides evidence of abrupt climate variations during the last glaciation. The pollen record reveals a pattern of high-frequency variations similar to that in ice cores as shown by oxygen isotopes or dust content. Analyses of 14 travertine samples yield coherent U-series ages in correct stratigraphic order, ranging from 40,000 to 70,000 yr. According to changes in the composition and structure of the vegetation, five paleoclimatic phases have been differentiated; the oldest, ranging from 70,200 to 65,500 yr ago, records thermophilous taxa which correspond to the last warm events of isotopic stage 5. The next phase, from 65,500 to 56,800 yr, records a cold, humid climate that correlates with isotope stage 4. During the third phase, from 56,800 to 49,500 yr, relatively warm and cold events alternate. The fourth phase, from 49,500 to 46,200 yr, records a cold, dry climate. The fifth phase, ranging from 46,200 to 40,800 yr, records a milder phase that is similar in appearance to the beginning of the Holocene.

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