Using paleoclimate data to constrain cloud parameterizations in GISS-E2.1

2021 ◽  
Author(s):  
Riovie D. Ramos ◽  
Allegra N. LeGrande ◽  
Michael L. Griffiths ◽  
Gregory S. Elsaesser ◽  
Daniel T. Litchmore ◽  
...  
Keyword(s):  
Large Scale ◽  
Ice Core ◽  
Water Isotopes ◽  
Isotope Tracers ◽  
Model Cloud ◽  
Convection Parameterization ◽  
The Last Glacial Maximum ◽  
Single Set ◽  
Better Than ◽  
The Last Glacial

<p>Much of the inter-model spread in equilibrium climate sensitivity (ECS) estimates is attributed to cloud and convective parameterizations which model cloud and water vapor feedbacks. These parameterizations also directly influence water isotopes, which may be retrieved not only from modern observations, but also a plethora of paleoclimate archives that represent a much broader range of variability than is available in modern measurements. And thus, these water isotope tracers can be used to constrain ECS by flagging unrealistic parts of the parameterization phase space via model biases in a perturbed parameterization ensemble (PPE) of paleoclimate simulations. In this proof-of-concept study, we evaluate a suite of isotope-enabled atmosphere-only GISS-E2.1 simulations, each with varying cloud and convective perturbations, against speleothem and ice core δ<sup>18</sup>O for the Last Glacial Maximum (LGM, 21000 years ago), mid-Holocene (MH, 6000 years ago) and pre-Industrial periods. The first-order spatial pattern of δ<sup>18</sup>O of precipitation (δ<sup>18</sup>O<sub>p</sub>) is in excellent agreement between proxy data and all parameterizations across all time periods. While the simulations generally capture large scale δ<sup>18</sup>O<sub>p</sub> patterns, the magnitude of change is consistently smaller in all simulations than those of the proxies, highlighting uncertainties in both models and proxies. Not a single set of parameterizations worked well in all climate states, indicating that improving future simulations requires determining all plausible parameter combinations critical in refining ECS. Further, it may be that certain parameterization choices represent certain types of variability better than others, and there may be a non-unique solution to ideal clouds/convection parameterization choices that is modulated by the question asked.</p>

scholarly journals Constraining clouds and convective parameterizations in a climate model from past climate

2021 ◽  
Author(s):  
Riovie Ramos ◽  
Allegra LeGrande ◽  
Michael Griffiths ◽  
Gregory Elsaesser ◽  
Daniel Litchmore ◽  
...  
Keyword(s):  
Climate Model ◽  
Climate Forcing ◽  
Proof Of Concept ◽  
Equilibrium Climate Sensitivity ◽  
Global Database ◽  
The World ◽  
The Last Glacial Maximum ◽  
Single Set ◽  
Better Than ◽  
The Last Glacial

Cloud and convective parameterizations strongly influence uncertainties in equilibrium climate sensitivity (ECS). We provide a proof-of-concept study to constrain these parameterizations in a perturbed parameter ensemble of atmosphere-only simulations by evaluating model biases in the present-day runs using multiple satellite climatologies and by comparing simulated δ18O of precipitation (δ18Op), known to be sensitive to parameterization schemes, with a global database of speleothem δ18O records covering the Last Glacial Maximum (LGM), mid-Holocene (MH) and pre-industrial (PI) periods. Relative to modern, paleoclimate simulations show greater sensitivity to parameter changes, allowing for an evaluation of uncertainties over a broader range of climate forcing and the identification of parts of the world that are parameter sensitive. Certain simulations reproduced LGM and MH δ18Op anomalies relative to the PI better than the default parameterization. Not a single set of parameterizations worked well in all climate states, thus improving simulations requires determining all plausible parameter combinations.

A new 14C age for the Oruanui (Wairakei) eruption, New Zealand

1988 ◽  
Vol 125 (3) ◽  
pp. 297-300 ◽  
Author(s):  
C. J. N. Wilson ◽  
V. R. Switsur ◽  
A. P. Ward
Keyword(s):  
New Zealand ◽  
Large Scale ◽  
Ice Core ◽  
14C Age ◽  
Bulk Volume ◽  
Oruanui Eruption ◽  
The Antarctic ◽  
The Last Glacial Maximum ◽  
Taupo Volcano ◽  
The Last Glacial

AbstractThe Oruanui eruption was the largest known outburst of Taupo volcano, New Zealand, and is among the larger Quaternary eruptions documented. The eruption deposits are variously known as the Oruanui, Wairakei, Kawakawa Tephra, or Aokautere Ash formations, and represent a bulk volume probably exceeding 500 km3. Four new 14C age determinations on carbonized vegetation in the non-welded Oruanui ignimbrite are combined to give a conventional age of 22590±230 yr b.p. Compared with the previously accepted figure of 20000 yr b.p., this new age resolves the anomaly of apparently older 14C ages being obtained from a demonstrably younger New Zealand deposit, and strengthens correlation of this eruption with an Antarctic ice-core acid anomaly. The trace of this eruption has great potential as a time-plane marker in the Antarctic just prior to the last glacial maximum. The close similarity in ages between the Oruanui and a comparable sized eruption (Ito/Aira-Tn) in Japan suggests that this period of activity may represent the best chance of resolving any linkages between large-scale explosive silicic volcanism and climate changes.

scholarly journals Glaciation and deglaciation mechanisms in a coupled two-dimensional climate—ice-sheet model

1993 ◽  
Vol 39 (131) ◽  
pp. 45-49 ◽  
Author(s):  
André Berger ◽  
Hubert Gallée ◽  
Christian Tricot
Keyword(s):  
Ice Core ◽  
Ice Sheets ◽  
Low Frequency ◽  
Two Dimensional ◽  
Atmospheric Concentration ◽  
Last Glacial ◽  
Simulated Climate ◽  
Milankovitch Theory ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract A two-dimensional model which links the atmosphere, the mixed layer of the ocean, the sea ice, the continents, the ice sheets and their underlying bedrock has been used to test the Milankovitch theory over the last glacial—interglacial cycle. It was found that the orbital variations alone can induce, in such a system, feed-backs sufficient to generate the low-frequency part of the climatic variations over the last 122 kyear. These simulated variations at the astronomical time-scale are broadly in agreement with ice volume and sea-level reconstructions independently obtained from geological data. Imperfections in the simulated climate were the insufficient southward extent of the ice sheets and the too small hemispheric cooling during the last glacial maximum. These deficiencies were partly remedied in a further experiment (Gallée and others, in press) by using the time-dependent CO2 atmospheric concentration given by the Vostok ice core in addition to the astronomical forcing. For this second experiment, the main mechanisms and feedbacks responsible for the glaciation and the deglaciation in the model are discussed here.

scholarly journals Site information and initial results from deep ice drilling on Law Dome, Antarctica

1997 ◽  
Vol 43 (143) ◽  
pp. 3-10 ◽  
Author(s):  
V.I. Morgan ◽  
C.W. Wookey ◽  
J. Li ◽  
T.D. van Ommen ◽  
W. Skinner ◽  
...  
Keyword(s):  
Ice Core ◽  
Ice Sheet ◽  
High Accumulation ◽  
Ice Flow ◽  
Ice Cap ◽  
Basal Ice ◽  
Inland Ice ◽  
The Last Glacial Maximum ◽  
Initial Results ◽  
The Last Glacial

AbstractThe aim of deep ice drilling on Law Dome, Antarctica, has been to exploit the special characteristics of Law Dome summit, i.e. low temperature and high accumulation near an ice divide, to obtain a high-resolution ice core for climatic/environmental studies of the Holocene and the Last Glacial Maximum (LGM). Drilling was completed in February 1993, when basal ice containing small fragments of rock was reached at a depth of 1196 m. Accurate ice dating, obtained by counting annual layers revealed by fine-detail δ18О, peroxide and electrical-conductivity measurements, is continuous down to 399 m, corresponding to a date of AD 1304. Sulphate concentration measurements, made around depths where conductivity tracing indicates volcanic fallout, allow confirmation of the dating (for Agung in 1963 and Tambora in 1815) or estimates of the eruption date from the ice dating (for the Kuwae, Vanuatu, eruption ~1457). The lower part of the core is dated by extrapolating the layer-counting using a simple model of the ice flow. At the LGM, ice-fabric measurements show a large decrease (250 to 14 mm2) in crystal size and a narrow maximum in c-axis vertically. The main zone of strong single-pole fabrics however, is located higher up in a broad zone around 900 m. Oxygen-isotope (δ18O) measurements show Holocene ice down to 1113 m, the LGM at 1133 m and warm (δ18O) about the same as Holocene) ice near the base of the ice sheet. The LGM/Holocene δ18O shift of 7.0‰, only ~1‰ larger than for Vostok, indicates that Law Dome remained an independent ice cap and was not overridden by the inland ice sheet in the Glacial.

scholarly journals Tropical Cyclone Genesis Factors in Simulations of the Last Glacial Maximum

2012 ◽  
Vol 25 (12) ◽  
pp. 4348-4365 ◽  
Author(s):  
Robert L. Korty ◽  
Suzana J. Camargo ◽  
Joseph Galewsky
Keyword(s):  
Tropical Cyclone ◽  
Last Glacial Maximum ◽  
Large Scale ◽  
Glacial Maximum ◽  
Tropical Cyclogenesis ◽  
Tropical Cyclone Genesis ◽  
Surface Cooling ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract Large-scale environmental factors that favor tropical cyclogenesis are calculated and examined in simulations of the Last Glacial Maximum (LGM) from the Paleoclimate Modelling Intercomparison Project Phase 2 (PMIP2). Despite universally colder conditions at the LGM, values of tropical cyclone potential intensity, which both serves as an upper bound on thermodynamically achievable intensity and indicates regions supportive of the deep convection required, are broadly similar in magnitude to those in preindustrial era control simulation. Some regions, including large areas of the central and western North Pacific, feature higher potential intensities at the LGM than they do in the control runs, while other regions including much of the Atlantic and Indian Oceans are lower. Changes in potential intensity are strongly correlated with the degree of surface cooling during the LGM. Additionally, two thermodynamic parameters—one that measures midtropospheric entropy deficits relevant for tropical cyclogenesis and another related to the time required for genesis—are broadly more favorable in the LGM simulation than in the preindustrial era control. A genesis potential index yields higher values for the LGM in much of the western Pacific, a feature common to nearly all of the individual models examined.

scholarly journals Global Speleothem Oxygen Isotope Measurements Since the Last Glacial Maximum

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
A. M. Shah ◽  
C. Morrill ◽  
E. P. Gille ◽  
W. S. Gross ◽  
D. M. Anderson ◽  
...  
Keyword(s):  
Oxygen Isotope ◽  
Last Glacial Maximum ◽  
Large Scale ◽  
Asian Summer Monsoon ◽  
Glacial Maximum ◽  
Last Glacial ◽  
Hydrologic Variability ◽  
The World ◽  
The Last Glacial Maximum ◽  
The Last Glacial

This synthesis of thirty-six sites (sixty cores with over 27 000 measurements) located around the world facilitates scientific research on the climate of the last 21 000 years ago obtained from oxygen isotope ( or delta-O-18) measurements. Oxygen isotopes in speleothem calcite record the influence of ambient temperature and the isotopic composition of the source water, the latter providing evidence of hydrologic variability and change. Compared to paleoclimate proxies from sedimentary archives, the age uncertainty is unusually small, around +/−100 years for the last 21 000-year interval. Using data contributed to the World Data Center (WDC) for Paleoclimatology, we have created consistently formatted data files for individual sites as well as composite dataset of annual to millennial resolution. These individual files also contain the chronology information about the sites. The data are useful in understanding hydrologic variability at local and regional scales, such as the Asian summer monsoon and the Intertropical Convergence Zone (as discussed in the underlying source publications), and should also be useful in understanding large-scale aspects of hydrologic change since the Last Glacial Maximum (LGM).

scholarly journals A Radiocarbon Perspective on Greenland Ice-Core Chronologies: Can we Use Ice Cores for 14C Calibration?

Radiocarbon ◽  
2004 ◽  
Vol 46 (3) ◽  
pp. 1239-1259 ◽  
Author(s):  
John Southon
Keyword(s):  
Last Glacial Maximum ◽  
Northern Hemisphere ◽  
Time Scale ◽  
Ice Core ◽  
Ice Cores ◽  
Strong Correlations ◽  
Crucial Importance ◽  
Proxy Records ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Some of the most valuable paleoclimate archives yet recovered are the multi-proxy records from the Greenland GISP2 and GRIP ice cores. The crucial importance of these data arises in part from the strong correlations that exist between the Greenland δ18O records and isotopic or other proxies in numerous other Northern Hemisphere paleoclimate sequences. These correlations could, in principle, allow layer-counted ice-core chronologies to be transferred to radiocarbon-dated paleoclimate archives, thus providing a 14C calibration for the Last Glacial Maximum and Isotope Stage 3, back to the instrumental limits of the 14C technique. However, this possibility is confounded by the existence of numerous different chronologies, as opposed to a single (or even a “best”) ice-core time scale. This paper reviews how the various chronologies were developed, summarizes the differences between them, and examines ways in which further research may allow a 14C calibration to be established.

scholarly journals Characteristics of air bubbles and hydrates in the Dome Fuji ice core, Antarctica

1999 ◽  
Vol 29 ◽  
pp. 207-210 ◽  
Author(s):  
Hideki Narita ◽  
Nobuhiko Azuma ◽  
Takeo Hondoh ◽  
Michiko Fujii ◽  
Mituo Kawaguchi ◽  
...  
Keyword(s):  
Last Glacial Maximum ◽  
Ice Core ◽  
Air Bubbles ◽  
Depth Range ◽  
Last Interglacial ◽  
Last Glacial ◽  
Maximum Period ◽  
Glacial Periods ◽  
The Last Glacial Maximum ◽  
The Last Glacial

AbstractAir bubbles trapped near the surface of an ice sheet are transformed into air hydrates below a certain depth Their volume and number varies partly with environment and climate. Air bubbles and hydrates at 120-2200 m depth in the Dome Fuji (Dome F) ice core were examined with a microscope. This depth range covers the Holocene/Last Glacial/Last Interglacial/Previous Glacial periods. No air bubbles were seen below about 1100 m depth, and air hydrates began to appear from about 600 m. The observed number of air bubbles and hydrates was similar to that found in the Vostok ice core. For the ice covering the Last Glacial Maximum period, however the hydrate concentration in the Dome F core is about half that of the Vostok core. Reference to snow metamorphism and packing does not explain this finding.

scholarly journals Comment on "Aerosol radiative forcing and climate sensitivity deduced from the Last Glacial Maximum to Holocene transition", by P. Chylek and U. Lohmann, Geophys. Res. Lett., 2008

2009 ◽  
Vol 5 (2) ◽  
pp. 143-145 ◽  
Author(s):  
J. C. Hargreaves ◽  
J. D. Annan
Keyword(s):  
Climate Sensitivity ◽  
Radiative Forcing ◽  
Ice Core ◽  
Short Term ◽  
Aerosol Radiative Forcing ◽  
Data Points ◽  
The Last Glacial Maximum ◽  
Aerosol Radiative ◽  
Selection Of ◽  
The Last Glacial

Abstract. In a recent paper, Chylek and Lohmann (2008) used data from the Vostok ice core together with simple energy balance arguments to simultaneously estimate both the dust radiative forcing effect and the climate sensitivity, generating surprisingly high and low values for these respective parameters. However, their results depend critically on their selection of single unrepresentative data points from time series which exhibit a large amount of short-term variability, and are highly unstable with respect to other arbitrarily selected data points. When temporal averages are used in accordance with accepted norms within the paleoclimate community, the results obtained are entirely unremarkable and in line with previous analyses.

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