Millennial scale monsoon variability in the northeastern Arabian Sea: A multiproxy approach

2020 ◽  
Author(s):  
Andreas Lückge ◽  
Jeroen Groeneveld ◽  
Martina Hollstein ◽  
Mahyar Mohtadi ◽  
Enno Schefuß ◽  
...  
Keyword(s):  
Arabian Sea ◽  
Hydrological Cycle ◽  
Ice Core ◽  
Ice Cores ◽  
Water Masses ◽  
Intermediate Water ◽  
Heinrich Events ◽  
And Shifts ◽  
Ice Core Records ◽  
Millennial Scale

<p>The Dansgaard-Oeschger oscillations and Heinrich events described in Greenland ice core records are also expressed in the climate of the tropical realm as for instance documented in Arabian Sea sediments. However, little is known about these fluctuations beyond the reach of the Greenland ice cores. Here, we present high-resolution organic- and inorganic geochemical, sedimentological as well as micropaleontological data from two cores retrieved off the coast of Pakistan, extending the monsoon record to the past 200,000 years in millennial scale resolution.</p><p>The stable oxygen isotope (δ<sup>18</sup>O) record of the planktic foraminifera G. ruber shows a strong correspondence to Greenland ice core δ<sup>18</sup>O, whereas the deepwater δ<sup>18</sup>O signal of benthic foraminifera (U. peregrina and G. affinis) reflects patterns similar to those observed in Antarctic ice core records. Strong shifts in benthic δ<sup>18</sup>O during stadials are interpreted to show frequent injections of oxygen-rich intermediate water masses of Southern Ocean origin into the Arabian Sea. Alkenone-derived SSTs vary between 23 and 28°C. Highest temperatures were encountered during interglacial MIS 5. Millennial scale SST changes of 2°C magnitude are modulated by long-term SST fluctuations. Interstadials (of glacial phases) and the cold phases of interglacials are characterized by sediments enriched in organic carbon (TOC) whereas sediments with low TOC contents appear during stadials. Abrupt shifts (50-60 year duration) at climate transitions, such as interstadial inceptions, correlate with changes in productivity-related and anoxia-indicating proxies. Interstadial inorganic data consistently show that enhanced fluxes of terrestrial-derived sediments are paralleled by productivity maxima, and are characterized by an increased fluvial contribution from the Indus River. The hydrogen isotopic composition of terrigenous plant waxes indicates that stadials are dry phases whereas humid conditions seem to have prevailed during interstadials. In contrast, stadials are characterized by an increased contribution of aeolian dust probably from the Arabian Peninsula. Heinrich events are especially dry and dusty, indicating a dramatically weakened Indian summer monsoon and increased continental aridity.</p><p>These results strengthen the evidence that North Atlantic temperature changes and shifts in the hydrological cycle of the Indian monsoon system are closely coupled, and had a massive impact on regional environmental conditions such as river discharge and ocean margin anoxia. These shifts were modulated by changes in the supply of water masses from the Southern Hemisphere.</p>

scholarly journals Multi-proxy fingerprint of Heinrich event 4 in Greenland ice core records

2014 ◽  
Vol 10 (2) ◽  
pp. 1179-1222 ◽  
Author(s):  
M. Guillevic ◽  
L. Bazin ◽  
A. Landais ◽  
C. Stowasser ◽  
V. Masson-Delmotte ◽  
...  
Keyword(s):  
Climate Model ◽  
Hydrological Cycle ◽  
Ice Core ◽  
Ice Cores ◽  
Meridional Overturning Circulation ◽  
Low Latitude ◽  
Abrupt Decrease ◽  
Heinrich Events ◽  
Sequence Of Events ◽  
Heinrich Event

Abstract. Glacial climate was characterised by two types of abrupt events. Greenland ice cores record Dansgaard–Oeschger events, marked by abrupt warming in-between cold, stadial phases. Six of these stadials coincide with major Heinrich events (HE), identified from ice-rafted debris (IRD) and large excursions in carbon and oxygen stable isotopic ratios in North Atlantic deep sea sediments, documenting major ice sheet collapse events. This finding has led to the paradigm that glacial cold events are induced by the response of the Atlantic Meridional Overturning Circulation to such massive freshwater inputs, supported by sensitivity studies conducted with climate models of various complexities. This mechanism could however never be confirmed or infirmed because the exact timing of Heinrich events and associated low latitude hydrological cycle changes with respect to Greenland stadials has so far remained elusive. Here, we provide the first multi-proxy fingerprint of H4 within Stadial 9 in Greenland ice cores through ice and air proxies of low latitude climate and water cycle changes. Our new dataset demonstrates that Stadial 9 consists of three phases, characterised first by Greenland cooling during 550 ± 60 years (as shown by markers of Greenland temperature δ18O and δ15N), followed by the fingerprint of Heinrich Event 4 as identified from several proxy records (abrupt decrease in 17O excess and Greenland methane sulfonic acid (MSA), increase in CO2 and methane mixing ratio, heavier δ D-CH4 and δ18Oatm), lasting 740 ± 60 years, itself ending approximately 390 ± 50 years prior to abrupt Greenland warming. Preliminary investigations on GS-13 encompassing H5, based on the ice core proxies δ18O, MSA, δ18Oatm, CH4 and CO2 data also reveal a 3 phase structure, as well as the same sequence of events. The decoupling between stable cold Greenland temperature and low latitude HE imprints provides new targets for benchmarking climate model simulations and testing mechanisms associated with millennial variability.

Reconstructing an Interdecadal Pacific Oscillation Index from a Pacific Basin–Wide Collection of Ice Core Records

2021 ◽  
Vol 34 (10) ◽  
pp. 3839-3852
Author(s):  
Stacy E. Porter ◽  
Ellen Mosley-Thompson ◽  
Lonnie G. Thompson ◽  
Aaron B. Wilson
Keyword(s):  
Ice Core ◽  
Ice Cores ◽  
Tropical Pacific ◽  
Ice Age ◽  
Pacific Basin ◽  
Interdecadal Pacific Oscillation ◽  
The Pacific ◽  
Instrumental Period ◽  
The Tropical Pacific ◽  
Ice Core Records

AbstractUsing an assemblage of four ice cores collected around the Pacific basin, one of the first basinwide histories of Pacific climate variability has been created. This ice core–derived index of the interdecadal Pacific oscillation (IPO) incorporates ice core records from South America, the Himalayas, the Antarctic Peninsula, and northwestern North America. The reconstructed IPO is annually resolved and dates to 1450 CE. The IPO index compares well with observations during the instrumental period and with paleo-proxy assimilated datasets throughout the entire record, which indicates a robust and temporally stationary IPO signal for the last ~550 years. Paleoclimate reconstructions from the tropical Pacific region vary greatly during the Little Ice Age (LIA), although the reconstructed IPO index in this study suggests that the LIA was primarily defined by a weak, negative IPO phase and hence more La Niña–like conditions. Although the mean state of the tropical Pacific Ocean during the LIA remains uncertain, the reconstructed IPO reveals some interesting dynamical relationships with the intertropical convergence zone (ITCZ). In the current warm period, a positive (negative) IPO coincides with an expansion (contraction) of the seasonal latitudinal range of the ITCZ. This relationship is not stationary, however, and is virtually absent throughout the LIA, suggesting that external forcing, such as that from volcanoes and/or reduced solar irradiance, could be driving either the ITCZ shifts or the climate dominating the ice core sites used in the IPO reconstruction.

scholarly journals Towards a quasi-complete reconstruction of past atmospheric aerosol load and composition (organic and inorganic) over Europe since 1920 inferred from Alpine ice cores

2013 ◽  
Vol 9 (4) ◽  
pp. 1403-1416 ◽  
Author(s):  
S. Preunkert ◽  
M. Legrand
Keyword(s):  
World War Ii ◽  
Organic Carbon ◽  
Atmospheric Aerosol ◽  
Ice Core ◽  
Ice Cores ◽  
Organic Aerosol ◽  
Water Soluble ◽  
Climate Forcing ◽  
World War ◽  
Ice Core Records

Abstract. Seasonally resolved chemical ice core records available from the Col du Dôme glacier (4250 m elevation, French Alps), are here used to reconstruct past aerosol load and composition of the free European troposphere from before World War II to present. Available ice core records include inorganic (Na+, Ca2+, NH4+, Cl−, NO3−, and SO42−) and organic (carboxylates, HCHO, humic-like substances, dissolved organic carbon, water-insoluble organic carbon, and black carbon) compounds and fractions that permit reconstructing the key aerosol components and their changes over the past. It is shown that the atmospheric load of submicron aerosol has been increased by a factor of 3 from the 1921–1951 to 1971–1988 years, mainly as a result of a large increase of sulfate (a factor of 5), ammonium and water-soluble organic aerosol (a factor of 3). Thus, not only growing anthropogenic emissions of sulfur dioxide and ammonia have caused the enhancement of the atmospheric aerosol load but also biogenic emissions producing water-soluble organic aerosol. This unexpected change of biospheric source of organic aerosol after 1950 needs to be considered and further investigated in scenarios dealing with climate forcing by atmospheric aerosol.

Tephra in the Greenland Ice cores: Insights into Icelandic volcano-climate impacts

2021 ◽  
Author(s):  
Imogen Gabriel ◽  
Gill Plunkett ◽  
Peter Abbott ◽  
Bergrún Óladóttir ◽  
Joseph McConnell ◽  
...  
Keyword(s):  
High Resolution ◽  
Ice Core ◽  
Ice Cores ◽  
Volcanic Eruptions ◽  
Climate Impacts ◽  
Geochemical Analysis ◽  
Volcanic Events ◽  
Societal Impacts ◽  
The Impact ◽  
Ice Core Records

<p>Volcanic eruptions are considered as one of the primary natural drivers for changes in the global climate system and understanding the impact of past eruptions on the climate is integral to adopt appropriate responses towards future volcanic eruptions.</p><p>The Greenland ice core records are dominated by Icelandic eruptions, with several volcanic systems (Katla, Hekla, Bárðarbunga-Veiðivötn and Grimsvötn) being highly active throughout the Holocene. A notable period of increased Icelandic volcanic activity occurred between 500-1250 AD and coincided with climatic changes in the North Atlantic region which may have facilitated the Viking settlement of Greenland and Iceland. However, a number of these volcanic events are poorly constrained (duration and magnitude). Consequently, the Greenland ice cores offer the opportunity to reliably reconstruct past Icelandic volcanism (duration, magnitude and frequency) due to their high-resolution, the proximity of Iceland to Greenland and subsequent increased likelihood of volcanic fallout deposits (tephra particles and sulphur aerosols) being preserved. However, both the high frequency of eruptions between 500-1250 AD and the geochemical similarity of Iceland’s volcanic centres present challenges in making the required robust geochemical correlations between the source volcano and the ice core records and ultimately reliably assessing the climatic-societal impacts of these eruptions.</p><p>To address this, we use two Greenland ice core records (TUNU2013 and B19) and undertake geochemical analysis on tephra from the volcanic events in the selected time window which have been detected and sampled using novel techniques (insoluble particle peaks and sulphur acidity peaks). Further geochemical analysis of proximal material enables robust correlations to be made between the events in the ice core records and their volcanic centres. The high-resolution of these polar archives provides a precise age for the event and when utilised alongside other proxies (i.e. sulphur aerosols), both the duration and magnitude of these eruptions can be constrained, and the climatic-societal impacts of these eruptions reliably assessed.</p>

Environmental records from polar ice cores

1990 ◽  
Vol 330 (1615) ◽  
pp. 459-462 ◽  
Keyword(s):  
Solar Activity ◽  
Ice Core ◽  
Ice Cores ◽  
Polar Ice ◽  
Cosmogenic Isotope ◽  
Wide Range ◽  
Recent Part ◽  
Ice Core Records

Polar ice cores provide a wide range of information on past atmospheric climate (temperature, precipitation) and environment (gas and aerosol concentrations). The dating can be very accurate for the more recent part of the records but accuracy decreases with depth and time. Measurements of cosmogenic isotope concentrations (such as 10 Be) provide information on palaeo-precipitation rates and particular events can be used to correlate ice core records. Besides these climatic applications, 10 Be concentration records in ice cores also contain information on solar activity changes.

scholarly journals Air–snow transfer of nitrate on the East Antarctic Plateau – Part 2: An isotopic model for the interpretation of deep ice-core records

2015 ◽  
Vol 15 (20) ◽  
pp. 12079-12113 ◽  
Author(s):  
J. Erbland ◽  
J. Savarino ◽  
S. Morin ◽  
J. L. France ◽  
M. M. Frey ◽  
...  
Keyword(s):  
Mass Fraction ◽  
Ice Core ◽  
Ice Cores ◽  
Reactive Nitrogen ◽  
Antarctic Plateau ◽  
Surface Snow ◽  
Rate Building ◽  
The Antarctic ◽  
The Impact ◽  
Ice Core Records

Abstract. Unraveling the modern budget of reactive nitrogen on the Antarctic Plateau is critical for the interpretation of ice-core records of nitrate. This requires accounting for nitrate recycling processes occurring in near-surface snow and the overlying atmospheric boundary layer. Not only concentration measurements but also isotopic ratios of nitrogen and oxygen in nitrate provide constraints on the processes at play. However, due to the large number of intertwined chemical and physical phenomena involved, numerical modeling is required to test hypotheses in a quantitative manner. Here we introduce the model TRANSITS (TRansfer of Atmospheric Nitrate Stable Isotopes To the Snow), a novel conceptual, multi-layer and one-dimensional model representing the impact of processes operating on nitrate at the air–snow interface on the East Antarctic Plateau, in terms of concentrations (mass fraction) and nitrogen (δ15N) and oxygen isotopic composition (17O excess, Δ17O) in nitrate. At the air–snow interface at Dome C (DC; 75° 06' S, 123° 19' E), the model reproduces well the values of δ15N in atmospheric and surface snow (skin layer) nitrate as well as in the δ15N profile in DC snow, including the observed extraordinary high positive values (around +300 ‰) below 2 cm. The model also captures the observed variability in nitrate mass fraction in the snow. While oxygen data are qualitatively reproduced at the air–snow interface at DC and in East Antarctica, the simulated Δ17O values underestimate the observed Δ17O values by several per mill. This is explained by the simplifications made in the description of the atmospheric cycling and oxidation of NO2 as well as by our lack of understanding of the NOx chemistry at Dome C. The model reproduces well the sensitivity of δ15N, Δ17O and the apparent fractionation constants (15ϵapp, 17Eapp) to the snow accumulation rate. Building on this development, we propose a framework for the interpretation of nitrate records measured from ice cores. Measurement of nitrate mass fractions and δ15N in the nitrate archived in an ice core may be used to derive information about past variations in the total ozone column and/or the primary inputs of nitrate above Antarctica as well as in nitrate trapping efficiency (defined as the ratio between the archived nitrate flux and the primary nitrate input flux). The Δ17O of nitrate could then be corrected from the impact of cage recombination effects associated with the photolysis of nitrate in snow. Past changes in the relative contributions of the Δ17O in the primary inputs of nitrate and the Δ17O in the locally cycled NO2 and that inherited from the additional O atom in the oxidation of NO2 could then be determined. Therefore, information about the past variations in the local and long-range processes operating on reactive nitrogen species could be obtained from ice cores collected in low-accumulation regions such as the Antarctic Plateau.

scholarly journals Multi-model comparison of the volcanic sulfate deposition from the 1815 eruption of Mt. Tambora

2017 ◽  
Author(s):  
Lauren Marshall ◽  
Anja Schmidt ◽  
Matthew Toohey ◽  
Ken S. Carslaw ◽  
Graham W. Mann ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Model Comparison ◽  
Ice Core ◽  
Ice Cores ◽  
Sulfate Aerosol ◽  
Polar Regions ◽  
Polar Ice ◽  
Climatic Effects ◽  
Sulfate Deposition ◽  
Ice Core Records

Abstract. The eruption of Mt. Tambora in 1815 was the largest volcanic eruption of the past 500 years. The eruption had significant climatic impacts, leading to the 1816 Year Without a Summer and remains a valuable event from which to understand the climatic effects of large stratospheric volcanic sulfur dioxide injections. The eruption also resulted in one of the strongest and most easily identifiable volcanic signals in polar ice cores, which are widely used to reconstruct the timing and atmospheric sulfate loading of past eruptions. As part of the Model Intercomparison Project on the climatic response to Volcanic forcing (VolMIP), four state-of-the-art global aerosol models simulated this eruption. We analyse both simulated background (no Tambora) and volcanic (with Tambora) sulfate deposition to polar regions and compare to ice core records. Background sulfate deposition is of similar magnitude across all models and compares well to ice core records. However, volcanic sulfate deposition varies in timing, spatial pattern and magnitude between the models. Mean simulated deposited sulfate on Antarctica ranges from 19 to 264 kg km−2, and on Greenland from 31 to 194 kg km−2, as compared to the mean ice core-derived estimates of roughly 40–50 kg km−2, for both Greenland and Antarctica. The ratio of the hemispheric atmospheric sulfate aerosol burden after the eruption to the average ice sheet deposited sulfate varies between models by up to a factor of 15. Sources of this inter-model variability include differences in both the formation and the transport of sulfate aerosol. Our results highlight the uncertainties and difficulties in deriving historic volcanic aerosol radiative forcing of climate, based on measured volcanic sulfate in polar ice cores.

scholarly journals Reconciling the surface temperature–surface mass balance relationship in models and ice cores in Antarctica over the last two centuries

2020 ◽  
Author(s):  
Marie G. P. Cavitte ◽  
Quentin Dalaiden ◽  
Hugues Goosse ◽  
Jan T. M. Lenaerts ◽  
Elizabeth R. Thomas
Keyword(s):  
Mass Balance ◽  
Large Scale ◽  
Ice Core ◽  
Ice Sheets ◽  
Ice Cores ◽  
Surface Mass Balance ◽  
Weak Correlation ◽  
Surface Mass ◽  
The Past ◽  
Ice Core Records

Abstract. Ice cores are an important record of the past surface mass balance (SMB) of ice sheets, with SMB mitigating the ice sheets’ sea level impact over the recent decades. For the Antarctic Ice Sheet (AIS), SMB is dominated by large-scale atmospheric circulation, which collects warm moist air from further north and releases it in the form of snow as widespread accumulation or focused atmospheric rivers on the continent. This implies that the snow deposited at the surface of the AIS should record strongly coupled SMB and surface air temperature (SAT) variations. Ice cores use δ18O as a proxy for SAT as they do not record SAT directly. Here, using isotope-enabled global climate models and the RACMO2.3 regional climate model, we calculate positive SMB-SAT and δ18O-SMB correlations over ∼90 % of the AIS. The high spatial resolution of the RACMO2.3 model allows us to highlight a number of areas where SMB and SAT are not correlated, and show that wind-driven processes acting locally, such as Foehn and katabatic effects, can overwhelm the large-scale atmospheric input in SMB and SAT responsible for the positive SMB-SAT correlations. We focus in particular on Dronning Maud Land, East Antarctica, where the ice promontories clearly show these wind-induced effects. However, using the PAGES2k ice core compilations of SMB and δ18O of Thomas et al. (2017) and Stenni et al. (2017), we obtain a weak correlation, on the order of 0.1, between SMB and δ18O over the past ~150 years. We obtain an equivalently weak correlation between ice core SMB and the SAT reconstruction of Nicolas and Bromwich (2014) over the past ~50 years, although the ice core sites are not spatially co-located with the areas displaying a low SMB-SAT correlation in the models. To resolve the discrepancy between the measured and modeled signals, we show that averaging the ice core records in close spatial proximity increases their SMB-SAT correlation. This increase shows that the weak measured correlation likely results from random noise present in the ice core records, but is not large enough to match the correlation calculated in the models. Our results indicate thus a positive correlation between SAT and SMB in models and ice core reconstructions but with a weaker value in observations that may be due to missing processes in models or some systematic biases in ice core data that are not removed by a simple average.

scholarly journals Archival processes of the water stable isotope signal in East Antarctic ice cores

2017 ◽  
Author(s):  
Mathieu Casado ◽  
Amaelle Landais ◽  
Ghislain Picard ◽  
Thomas Münch ◽  
Thomas Laepple ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Climate Models ◽  
Ice Core ◽  
Ice Cores ◽  
Climatic Conditions ◽  
Antarctic Plateau ◽  
Surface Snow ◽  
Rayleigh Distillation ◽  
The Difference ◽  
Ice Core Records

Abstract. The oldest ice core records are obtained from the East Antarctic plateau. Water isotopes records are key to reconstructing past climatic conditions over the ice sheet and at the evaporation source. The accuracy of climate reconstructions depends on knowledge of all the processes affecting water vapour, precipitation and snow isotopic compositions. Fractionation processes are well understood and can be integrated in Rayleigh distillation and isotope enabled climate models. However, a quantitative understanding of processes potentially altering the snow isotopic composition after the deposition is still missing. In low accumulation sites, such as those found in Antarctica, these poorly constrained processes are likely to play a significant role and limit the interpretation of isotopic composition. Here, we combine observations of isotopic composition in the vapour, the precipitation, the surface snow and the buried snow from Dome C, a deep ice core site on the East Antarctic Plateau. At the seasonal scale, we suggest a significant impact of metamorphism on surface snow isotopic signal compared to the initial precipitation signal. Particularly, in summer, exchanges of water molecules between vapour and snow are driven by the sublimation/condensation cycles at the diurnal scale. Using highly resolved isotopic composition profiles from pits in five Antarctic sites, we identify common patterns, despite different accumulation rates, which cannot be attributed to the seasonal variability of precipitation. Altogether, the difference in the signals observed in the precipitation, surface snow and buried snow isotopic composition constitute evidences of post-deposition processes affecting ice core records in low accumulation areas.

Comparison of isotopic signatures in ice core and speleothem records to an isotope enabled climate model simulation for the last millennium

2021 ◽  
Author(s):  
Yannick Heiser ◽  
Janica Bühler ◽  
Mathieu Casado ◽  
Kira Rehfeld
Keyword(s):  
Climate Variability ◽  
Climate Model ◽  
Southern Oscillation ◽  
Ice Core ◽  
Ice Cores ◽  
Isotope Ratios ◽  
Last Millennium ◽  
Polar Ice ◽  
Geophysical Research ◽  
Ice Core Records

<div> <div> <div> <p>Stable water isotope ratios (δ18O) measured in e.g. ice-cores or speleothems have long been established as temperature proxies and are used to reconstruct past climate variability but still require more quantification on spatial and temporal scales. The high resolution ice-core archives are mainly found in polar and alpine regions, whereas the speleothem records mostly grow in caves in low to mid-latitudes. To bridge between the archives, models are needed to compare the climate variability stored in both ice-cores and speleothems, which will help to evaluate future projections of climate variability.</p> <p>Here, we compare a transient isotope enabled simulation from the Hadley Center Climate Model version 3 (iHadCM3) [1, 2] to polar ice-core records from the iso2k database [3] for the last millennium (LM, 850-1850 CE). We analyze time-averaged isotope ratios and their variability on decadal to centennial timescales to systematically evaluate the offsets and correlation patterns between simulated and recorded isotopes to specific climatic drivers. For better comparability between speleothem and ice core-archives, we also include non-polar ice core records, as well as monitored precipitation δ18O from a global database.</p> <p>We find the time-averaged δ18O offsets between the simulation and ice-core records to be fairly small for most of the polar ice-core sites, indicating a low simulation climate offset.<br>As expected, we find the simulated δ18O variability to be higher in the polar regions of ice-core locations, compared to the simulated variability at speleothem cave locations. Recorded δ18O variability is also generally higher as stored in ice-cores, compared to that stored in speleothems. Both speleothems and ice-core records show damping effects on decadal time scales, which can in part be attributed to the temporal resolution of the individual records. This comparison of different proxy archives to isotope-enabled GCM output shows a promising way to evaluate the model’s capability to resolve δ18O variability.</p> <div> <div> <div> <p>[1]  Bühler, J. C. et al. Comparison of the oxygen isotope signatures in speleothem records and iHadCM3 model simulations for the last millennium. Climate of the Past: Discussions 1–30 (2020).</p> <p>[2]  Tindall, J. C., Valdes, P. J. & Sime, L. C. Stable water isotopes in HadCM3: Isotopic signature of El Niño-Southern Oscillation and the tropical amount effect. Journal of Geophysical Research Atmospheres 114, 1–12 (2009).</p> <p>[3] Konecky, B. L. et al. The Iso2k database: A global compilation of paleo-δ18O and δ2H records to aid understanding of Common Era climate. Earth System Science Data 12, 2261–2288 (2020).</p> </div> </div> </div> </div> </div> </div>

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