TL;DR: In this paper, the isotope composition of snow in Greenland with meteorological and climatic parameters has been linked with the past few hundred years measured in ice cores using a new record of isotope values from the Greenland Ice Sheet Project 2 and Greenland Ice Core Project sites at Summit, Greenland.
Abstract: Recent efforts to link the isotopic composition of snow in Greenland with meteorological and climatic parameters have indicated that relatively local information such as observed annual temperatures from coastal Greenland sites, as well as more synoptic scale features such as the North Atlantic Oscillation (NAO) and the temperature seesaw between Jakobshaven, Greenland, and Oslo, Norway, are significantly correlated with δ18O and δD values from the past few hundred years measured in ice cores. In this study we review those efforts and then use a new record of isotope values from the Greenland Ice Sheet Project 2 and Greenland Ice Core Project sites at Summit, Greenland, to compare with meteorological and climatic parameters. This new record consists of six individual annually resolved isotopic records which have been average to produce a Summit stacked isotope record. The stacked record is significantly correlated with local Greenland temperatures over the past century (r=0.471), as well as a number of other records including temperatures and pressures from specific locations as well as temperature and pressure patterns such as the temperature seesaw and the North Atlantic Oscillation. A multiple linear regression of the stacked isotope record with a number of meteorological and climatic parameters in the North Atlantic region reveals that five variables contribute significantly to the variance in the isotope record: winter NAO, solar irradiance (as recorded by sunspot numbers), average Greenland coastal temperature, sea surface temperature in the moisture source region for Summit (30°–20°N), and the annual temperature seesaw between Jakobshaven and Oslo. Combined, these variables yield a correlation coefficient of r=0.71, explaining half of the variance in the stacked isotope record.
One of the great strengths of ice cores as proxies for past environmental conditions is that they can provide not only the long timescale necessary to view the large changes of the past glacial periods but also the high temporal resolution needed to look at socially relevant timescales, that is, subannual to decadal changes in climate and environmental conditions.
A total of six cores in the Summit region were drilled, sampled, and measured with sufficient temporal detail to calculate annual isotopic values.
The results of these studies are reviewed below.
3.2.1. Comparison with coastal temperatures. On the basis of both theoretical considerations and observations, stable
Isotope ratios of polar snows are commonly interpreted in terms of temperatures [Dansgaard, 1964] .
This approach depends on several key assumptions but is generally accepted as a very good first-order interpretation.
In all cases, except for the comparison with coastal temperatures mentioned earlier, the correlations with the stacked record were higher than the correlations with individual records.
Figure 6b shows the stacked isotopic record versus annual, winter (December-January-February.
TL;DR: Climate phases of ENSO have major effects on the spatial patterns ofδ(18)O, δ(2)H and d-excess values, being especially important on a seasonal basis in the Desert Southwest.
Abstract: RATIONALE Isotope (δ(18)O and δ(2)H values) ratios in precipitation have been central to understanding changes in Earth's climate as recorded in ice, coral, speleothems, lake varves and long-lived plants. Understanding how climate phases (i.e. ENSO) affect the spatial and temporal patterns of δ(18)O and δ(2)H values in precipitation has, however, been uncertain across the USA. METHODS A spatial precipitation isotope network (USNIP) has been established that aims to: (1) characterize the δ(18)O, δ(2)H and d-excess values in precipitation across the USA with the highest spatially dense network of measurements yet undertaken; (2) quantify the annual and seasonal patterns of precipitation δ(18)O and δ(2)H values that may be affected by ENSO climate phases; and (3) provide a new isotope database for scientific studies that can be incorporated into NEON, BASIN, GNIP, and IsoMAP. RESULTS On average, precipitation δ(18)O and δ(2)H values are very low in the northern Rocky Mountain region (~ -15‰ δ(18)O, and ~ -120‰ δ(2)H), and precipitation δ(18)O and δ(2)H values are relatively higher along the Gulf Coast (~ -5‰ δ(18)O and -10‰ δ(2)H) and in the Southeast. During El Nino periods the precipitation δ(18)O and δ(2)H values are lowest in northwest Montana, with precipitation that is depleted in (18)O and (2)H extending into northern Colorado, while moisture that is enriched in (18)O and (2)H continues to dominate the Gulf Coast. The annual average differences between the climate phases generally show especially depleted (18)O and (2)H in precipitation across the Rocky Mountain region during El Nino, compared with Neutral periods. CONCLUSIONS Detailed spatial and seasonal patterns of δ(18)O, δ(2)H and d-excess values provide fine-scale resolution not previously recognized. Climate phases of ENSO have major effects on the spatial patterns of δ(18)O, δ(2)H and d-excess values, being especially important on a seasonal basis in the Desert Southwest.
TL;DR: A review of climatic variability is given with a focus on abrupt changes during the last glacial as discussed by the authors, which were most likley due to reorganisations of the atmosphere-ocean system.
Abstract: A review of climatic variability is given with a focus on abrupt changes during the last glacial. Evidence from palaeoclimatic archives suggests that these were most likley due to reorganisations of the atmosphere–ocean system. The mechanisms responsible for these changes are presented. Their implication for future climate changes is discussed in light of recent climate model simulations.
55 citations
Cites background from "The climate signal in the stable is..."
...However, isotopic analysis of corals has the potential to reconstruct past El Niño events (Quinn et al. 1998), and the NAO has been recently detected in ice cores from Greenland (White et al. 1997; Appenzeller et al. 1998a; Appenzeller et al. 1998b)....
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...1998), and the NAO has been recently detected in ice cores from Greenland (White et al. 1997; Appenzeller et al. 1998a; Appenzeller et al. 1998b)....
TL;DR: In this article, the authors evaluated the extent to which inclusion of monthly moisture source temperature and moisture source locations in the Rayleigh distillation model aid in reproducing the relationships between monthly time series of precipitation isotope (δ 18 O) values and temperature across the contiguous United States.
Abstract: [1] Understanding and modeling precipitation isotope (δ 18 O and 6D) patterns for large regions of the globe requires quantifying processes governing continental-scale climatology and hydrology. In this study, we have evaluated the extent to which inclusion of monthly moisture source temperature and moisture source locations in the Rayleigh distillation model aid in reproducing the relationships between monthly time series of precipitation isotope (δ 18 O) values and temperature across the contiguous United States. The steepest isotope-temperature slopes (0.5‰-0.6‰ δ 18 O/°C) and greatest δ 18 O value correlations with temperature (r 2 = 0.5-0.8), derived from 5 continuous years of the data from the United States Network for Isotopes in Precipitation, occurred in the high altitudes of the Rocky Mountains and the upper Great Lakes region. The isotope-temperature slopes derived from the site-specific time series were consistently lower along the coastal regions of the United States as were the coefficients of determination. The low coastal isotope-temperature slopes are not easily explained by the simple Rayleigh model that uses condensation temperatures as the primary driver of precipitation isotopes. However, the Raleigh model equipped with moisture source temperatures defined by seasonal temperature oscillations and migrating moisture source locations provides a robust replication of the δ 18 O-temperature slopes along coastal regions. These findings emphasize the importance of moisture sources conditions when interpreting palaeoclimate proxies (i.e., tree rings, ice cores, etc.), and argue that moisture source dynamics should always be included in models that use isotopes as diagnostic tools in testing hydrologic models.
48 citations
Cites background from "The climate signal in the stable is..."
...[3] Empirical observations indicate that surface temperatures often account for more than half of the variance in precipitation d18O values [Rozanski et al., 1993; Shuman et al., 1995; White et al., 1997]....
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...[3] Empirical observations indicate that surface temperatures often account for more than half of the variance in precipitation d(18)O values [Rozanski et al., 1993; Shuman et al., 1995; White et al., 1997]....
TL;DR: In this article, a 58m-long sediment core was recovered in the southwestern part of the Okhotsk Sea for high resolution paleocenography, and an age model of the core was obtained by accelerator mass spectrometry (AMS) 14C dating of planktonic foraminifer shells, oxygen-isotope stratigraphy of benthic calcite, and tephrochronology, resulting in a core-bottom age of 115kyr.
Abstract: A 58-m-long sediment core IMAGES MD01-2412 was recovered in the southwestern part of the Okhotsk Sea for high resolution paleocenography. An age model of the core was obtained by accelerator mass spectrometry (AMS) 14C dating of planktonic foraminifer shells, oxygen–isotope stratigraphy of benthic foraminifer calcite, and tephrochronology, resulting in a core-bottom age of 115 kyr. Sea-ice expansion in the Okhotsk Sea was reconstructed by ice-rafted debris (IRD) based on measurement of dropstone, coarse fraction, sand fractions of terrigenous particles, and the magnetic properties. The SW Okhotsk Sea has not had perennial but seasonal sea-ice conditions during the 115 kyr. Seasonal sea ice fluctuated with large amplitudes on millennial scale during the glacials (Marine isotope stage: MIS 2, 3, and 4) and varied relatively little during the Holocene (MIS 1) and the last interglacial (MIS 5). Enhanced polar atmospheric circulation during the glacial resulted in strong wind fields over the Okhotsk Sea and accelerated the large sea-ice expansion during the glacials (MIS 2, 3, and 4). During the interglacials (MIS 1 and 5), sea ice also expanded by small amplitudes. During these periods, decrease of the Amur River discharge would be one of the possible factors for sea-ice expansion. The two main factors of polar atmospheric circulation and Amur River discharge would be responsible for sea-ice expansion during 120 kyr.
46 citations
Cites methods from "The climate signal in the stable is..."
...GISP2 ice-core oxygen isotope change (Dansgaard et al., 1993; Steiget et al., 1994; White et al., 1997; Stuiver et al., 1995)....
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...…temperature (alkenone SST) record (Harada et al., 2006-this volume) by graphical correlation with the
68 T. Sakamoto et al. / Global and Planetary Change 53 (2006) 58–77
GISP2 ice-core oxygen isotope change (Dansgaard et al., 1993; Steiget et al., 1994; White et al., 1997; Stuiver et al., 1995)....
TL;DR: In this article, a stacked water isotope record for Summit, central Greenland, has been established covering approximately the last 900 years and measurements of δ18O and δD in the GRIP deep ice core and the 230m core, S93, allow the reconstruction of a millennial record of the deuterium excess in a near-annual resolution.
Abstract: A stacked water isotope record for Summit, central Greenland, has been established covering approximately the last 900 years. Measurements of δ18O and δD in the GRIP deep ice core and the 230-m core, S93, allow the reconstruction of a millennial record of the deuterium excess in a near-annual resolution. A short period of particularly high values of the Deuterium Excess at the beginning of the fourteenth century may be associated with the medieval warm period (MWP). The Little Ice Age (LIA) might be represented by a 100-year period of very low excess values in the sixteenth and seventeenth centuries. Using a simple isotope model, δ18O and deuterium excess are interpreted in terms of surface temperature variations over central Greenland and over the subtropical North Atlantic, Greenland's principal vapor source region. An estimated cooling of −0.7°C of subtropical sea surface temperatures (SSTs) during the Little Ice Age and a warming of 0.6°C during the short warm period in the medieval is in agreement with previous studies. Over periods of about 100 years, an antiphasing between gradually decreasing δ18O and increasing deuterium excess is observed. Interannual-to-decadal-scale variability associated to the North Atlantic Oscillation may be responsible for this anti-phase relationship. An alternative explication is a North-South oscillation in North Atlantic sea surface temperatures associated with short-term changes in the thermohaline circulation.
TL;DR: In this paper, the isotopic fractionation of water in simple condensation-evaporation processes is considered quantitatively on the basis of the fractionation factors given in section 1.2.
Abstract: In chapter 2 the isotopic fractionation of water in some simple condensation-evaporation processes are considered quantitatively on the basis of the fractionation factors given in section 1.2. The condensation temperature is an important parameter, which has got some glaciological applications. The temperature effect (the δ's decreasing with temperature) together with varying evaporation and exchange appear in the “amount effect” as high δ's in sparse rain. The relative deuterium-oxygen-18 fractionation is not quite simple. If the relative deviations from the standard water (S.M.O.W.) are called δ D and δ 18 , the best linear approximation is δ D = 8 δ 18 . Chapter 3 gives some qualitative considerations on non-equilibrium (fast) processes. Kinetic effects have heavy bearings upon the effective fractionation factors. Such effects have only been demonstrated clearly in evaporation processes, but may also influence condensation processes. The quantity d = δ D −8 δ 18 is used as an index for non-equilibrium conditions. The stable isotope data from the world wide I.A.E.A.-W.M.O. precipitation survey are discussed in chapter 4. The unweighted mean annual composition of rain at tropical island stations fits the line δ D = 4.6 δ 18 indicating a first stage equilibrium condensation from vapour evaporated in a non-equilibrium process. Regional characteristics appear in the weighted means. The Northern hemisphere continental stations, except African and Near East, fit the line δ D = 8.0 δ 18 + 10 as far as the weighted means are concerned (δ D = 8.1 δ 18 + 11 for the unweighted) corresponding to an equilibrium Rayleigh condensation from vapour, evaporated in a non-equilibrium process from S.M.O.W. The departure from equilibrium vapour seems even higher in the rest of the investigated part of the world. At most stations the δ D and varies linearily with δ 18 with a slope close to 8, only at two stations higher than 8, at several lower than 8 (mainly connected with relatively dry climates). Considerable variations in the isotopic composition of monthly precipitation occur at most stations. At low latitudes the amount effect accounts for the variations, whereas seasonal variation at high latitudes is ascribed to the temperature effect. Tokyo is an example of a mid latitude station influenced by both effects. Some possible hydrological applications are outlined in chapter 5. DOI: 10.1111/j.2153-3490.1964.tb00181.x
TL;DR: In this article, the authors present the complete oxygen isotope record for the Greenland Ice Sheet Project 2 (GISP2) core, drilled 28 km west of the GRIP core, and observe large, rapid climate fluctuations throughout the last glacial period.
Abstract: RECENT results1,2 from the Greenland Ice-core Project (GRIP) Summit ice core suggest that the climate in Greenland has been remarkably stable during the Holocene, but was extremely unstable for the time period represented by the rest of the core, spanning the last two glaciations and the intervening Eemian inter-glacial. Here we present the complete oxygen isotope record for the Greenland Ice Sheet Project 2 (GISP2) core, drilled 28 km west of the GRIP core. We observe large, rapid climate fluctuations throughout the last glacial period, which closely match those reported for the GRIP core. However, in the bottom 10% of the cores, spanning the Eemian interglacial and the previous glacia-tion, there are significant differences between the two records. It is possible that ice flow may have altered the chronological sequences of the stratigraphy for the bottom part of one or both of the cores. Considerable further work will be necessary to evaluate the likelihood of this, and the extent to which it will still be possible to extract meaningful climate information from the lowest sections of the cores.
TL;DR: Measured 18O/16O ratios from the Greenland Ice Sheet Project 2 (GISP2) ice core extending back to 16,500 cal yr B.P. provide a continuous record of climate change since the last glaciation as discussed by the authors.
TL;DR: In this paper, the authors investigated the well-known tendency for winter temperatures to be low over northern Europe when they are high over Greenland and the Canadian Arctic, and conversely, they found that these pressure anomalies are so distributed that the pressure in the region of the Icelandic low is negatively correlated with the pressure over the North Pacific Ocean and over the area south of 50°N in the North Atlantic Ocean, Mediterranean and Middle East.
Abstract: We have investigated the well-known tendency for winter temperatures to be low over northern Europe when they are high over Greenland and the Canadian Arctic, and conversely. Well-defined pressure anomalies over most of the Northern Hemisphere are associated with this regional seesaw in temperature, and these pressure anomalies are so distributed that the pressure in the region of the Icelandic low is negatively correlated with the pressure over the North Pacific Ocean and over the area south of 50°N in the North Atlantic Ocean, Mediterranean and Middle East, but positively correlated with the pressure over the Rocky Mountains. The composite patterns of pressure anomalies in the seesaw are almost identical to the fist eigenvector in the monthly mean pressure, but the standard deviations of pressure anomalies in seesaw mouths are as large as the standard deviations of monthly means in general. Since 1840 the seesaw, as defined by temperatures in Scandinavia and Greenland, occurred in more than 40%...
TL;DR: In this paper, the authors compared the North Atlantic Oscillation (NAO) and Southern Oscillations (SO) from the standpoint of their association with Northern Hemisphere winter mean distributions of sea-level pressure (SLP) and 500 mb height.
Abstract: The North Atlantic Oscillation (NAO) and Southern Oscillation (SO) are compared from the standpoint of their association with Northern Hemisphere winter mean distributions of sea-level pressure (SLP) and 500 mb height. The NAO and SO are associated with significant SLP differences over much of the hemisphere except for Siberia and western North America. Significant SLP and 500 mb height differences occur in the NAO over the Atlantic Ocean and near Baja California, while in the SO they occur over the Pacific Ocean, India and the western Atlantic. Only over the latter region do large pressure and height variations consistently occur in the extremes of both oscillations; these are also associated with winter temperature variability over the southeastern United States. For example, during winter 1982–83, when the two oscillations simultaneously reached extremes, the NAO was associated with record December warmth east of the Mississippi River, but during January and February the SO dominated the heigh...