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: In this article, the authors synthesize data from five snow cores, covering the period 1932-96, from the sector 16˚38’ W −4˚48’ E in coastal Dronning Maud Land (DML), Antarctica.
Abstract: To investigate recent variability in accumulation and δ18O, we synthesize data from five snow cores, covering the period 1932–96, from the sector 16˚38’ W–4˚48’ E in coastal Dronning Maud Land (DML), Antarctica. the δ18O records from the different sites are remarkably similar and suggest a common stable moisture source for this coastal section of DML. While the accumulation pattern is local, and specific features restricted to the individual sites, the overall accumulation pattern is related to the temperature variability as indicated by coastal instrumental records. Accumulation and δ18O correlate between 1955 and 1985 but deviate thereafter, with the proxy-temperature record showing a positive trend while accumulation decreased. This occurs at the same time as an increase in sea-ice extent in the area, which may have resulted in circulation changes and more northerly storm paths. Both stacked accumulation and δ18O records show that large-scale atmospheric signals, as well as some pronounced individual events, are recorded in DML coastal ice cores.
TL;DR: This article analyzed 86 years of multiple modern coral δ18O records in the tropical Pacific and revealed a basin-scale decadal pattern of variability, consistent with recent studies based on instrumental data and coupled climate model studies, in which advection of thermal anomalies leads to El Nino/Southern Oscillation-like variability on decadal timescales.
Abstract: Analysis of 86 years of multiple modern coral δ18O records in the tropical Pacific reveals a basin-scale decadal pattern of variability. Although coral δ18O records the effects of both temperature and seawater δ18O variability due to salinity effects, in practice, most of the records used here agree well with observations of sea surface temperature on longer timescales. These coral proxy records reveal strong variability near a 12-year period. Their relative phasing suggests a signal propagating from the southwestern subtropical Pacific to other regions. The results are consistent with recent studies based on instrumental data and with coupled climate model studies, in which advection of thermal anomalies leads to El Nino/Southern Oscillation-like variability on decadal timescales. Additionally, there is evidence for a significant shift in many of the time series, along with a decrease in the decadal variability, occurring in the early 1940s. Finally, the proxy records indicate the presence of strong teleconnections between the eastern tropical Pacific and high latitude climate.
TL;DR: In this article, the authors investigated how variations in Arctic sea ice and sea surface conditions influence δ18O of present-day Arctic precipitation using the isoCAM3, an isotope-equipped version of the National Center for Atmospheric Research Community Atmosphere Model version 3.
Abstract: . This study investigates how variations in Arctic sea ice and sea surface conditions influence δ18O of present-day Arctic precipitation. This is done using the model isoCAM3, an isotope-equipped version of the National Center for Atmospheric Research Community Atmosphere Model version 3. Four sensitivity experiments and one control simulation are performed with prescribed sea surface temperature (SST) and sea ice. Each of the four experiments simulates the atmospheric and isotopic response to Arctic oceanic conditions for selected years after the beginning of the satellite era in 1979. Changes in sea ice extent and SSTs have different impacts in Greenland and the rest of the Arctic. The simulated changes in central Arctic sea ice do not influence δ18O of Greenland precipitation, only anomalies of Baffin Bay sea ice. However, this does not exclude the fact that simulations based on other sea ice and sea surface temperature distributions might yield changes in the δ18O of precipitation in Greenland. For the Arctic, δ18O of precipitation and water vapour is sensitive to local changes in sea ice and sea surface temperature and the changes in water vapour are surface based. Reduced sea ice extent yields more enriched isotope values, whereas increased sea ice extent yields more depleted isotope values. The distribution of the sea ice and sea surface conditions is found to be essential for the spatial distribution of the simulated changes in δ18O.
18 citations
Cites background from "The climate signal in the stable is..."
...It has become clear that
the isotopic composition of precipitation is a complex signal, influenced by both local and regional20
climate conditions (Vinther et al., 2010; Steen-Larsen et al., 2011; Sjolte et al., 2011; Sodemann
et al., 2008b; White et al., 1997; Johnsen et al., 1989)....
[...]
...It has become clear that the isotopic composition of precipitation is a complex signal, influenced by both local and regional climate conditions (Vinther et al., 2010; Steen-Larsen et al., 2011; Sjolte et al., 2011; Sodemann et al., 2008b; White et al., 1997; Johnsen et al., 1989)....
TL;DR: This paper showed that the stochastic-resonance hypothesis is consistent with a wider range of previously published data than analyzed before including a north Atlantic marine record and the Byrd Station, Antarctica ice-isotopic record; however, a record of hematite-stained quartz grains in north Atlantic sediment appears more periodic than stochastically resonant.
Abstract: The large, abrupt, widespread, millennial changes recorded in many paleoclimatic archives pose a major challenge to our understanding of the climate system. Both periodic and stochastic models have been proposed to explain these events. We have argued that Greenland ice-core data are more consistent with a stochastic-resonance hypothesis. In this model, a combination of a weak periodicity plus noise perhaps caused by ice-sheet-related changes in freshwater flux to the north Atlantic produced switches between warm and cold climate modes. Here, we show that the stochastic-resonance hypothesis is consistent with a wider range of previously published data than analyzed before including a north Atlantic marine record and the Byrd Station, Antarctica ice-isotopic record; however, a record of hematite-stained quartz grains in north Atlantic sediment appears more periodic than stochastically resonant.
TL;DR: In this paper, the authors investigate the evolution of snow temperature, water content, density and stable water isotopes of δ 18 O at four Arctic snow-pit sites during early-season melt, in order to understand the effects of melt on snowpack stratigraphies and seasonal isotopic signals.
Abstract: We investigate the evolution of snow temperature, water content, density and stable water isotopes of δ 18 O at four Arctic snow-pit sites during early-season melt, in order to understand the effects of melt on snowpack stratigraphies and seasonal isotopic signals. We relate isotopic changes observed at these sites to temperature reconstructions derived from a 33 year firn-core record drilled on the same icefield. Decreases in seasonal isotopic amplitudes observed at all but one snow-pit site coincide with the percolation of more enriched meltwater into the snowpack, suggesting that meltwater percolation is the dominant process causing isotopic redistribution in Arctic snowpacks during the melt season. The decrease in isotopic range was accompanied by increases in mean δ 18 O values at all snow-pit sites. Positive degree-day (PDD) calculations are used to relate the amount of melt observed at the low-elevation snow-pit sites to the firn-core site. Results based on PDD values suggest an average overestimation of 1.1°C in average annual temperature reconstructions from the firn-core site from 1967 to 2006, with the possibility of errors in excess of 3°C during high-melt years.
18 citations
Cites background from "The climate signal in the stable is..."
...Temporal slopes reported by White and others (1997) for Greenland ice cores range between 0....
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...