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Journal ArticleDOI

The climate signal in the stable isotopes of snow from Summit, Greenland: Results of comparisons with modern climate observations

30 Nov 1997-Journal of Geophysical Research (John Wiley & Sons, Ltd)-Vol. 102, pp 26425-26439

AbstractRecent 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.

Summary (1 min read)

Introduction

  • 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.

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The climate signal in the stable isotopes of snow from
Summit, Greenland: Results of comparisons with
modern climate observations
J. White, L. Barlow, D. Fisher, P. Grootes, J. Jouzel, S. Johnsen, M. Stuiver,
H. Clausen
To cite this version:
J. White, L. Barlow, D. Fisher, P. Grootes, J. Jouzel, et al.. The climate signal in the stable
isotopes of snow from Summit, Greenland: Results of comparisons with modern climate observa-
tions. Journal of Geophysical Research. Oceans, Wiley-Blackwell, 1997, 102 (C12), pp.26425-26439.
�10.1029/97JC00162�. �hal-03335034�

JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 102, NO. C12, PAGES 26,425-26,439, NOVEMBER 30, 1997
The climate signal in the stable isotopes of snow
from Summit, Greenland:
Results of comparisons with modern climate observations
J. W. C. White, •,2 L. K. Barlow, D. Fisher, 3 P. Grootes, 4,s
J. Jouzel, 6 S. J. Johnsen, ?,8 M. Stuiver, 4 and H. Clausen ?
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 8180 and 8D 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
(30ø-20øN), 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.
1. Introduction
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 dec-
adal changes in climate and environmental conditions. In the
past the focus in ice-core research, particularly for stable iso-
topes, has been mostly on the long timescales, with less em-
1Institute of Arctic and Alpine Research, University of Colorado,
Boulder.
2Also at Department of Geological Sciences, University of Colo-
rado, Boulder.
3Glaciology Section, Terrain Sciences Division, Geological Survey of
Canada, Ottawa, Ontario.
4Department of Geological Sciences and Quaternary Research Cen-
ter, University of Washington, Seattle.
SNow at Liebniz Laboratory, Christian Albrechts University, Kiel,
Germany.
6Laboratoire de Mod•lisation du Climat et de l'Environnement,
Centre d'Etudes de Saclay, Gif-sur-Yvette, France.
7Department of Geophysics, University of Copenhagen, Copenha-
gen, Denmark.
8Also at Science Institute, University of Reykjavik, Reykjavik, Ice-
land.
Copyright 1997 by the American Geophysical Union.
Paper number 97JC00162.
0148-0227/97/97JC-00162509.00
phasis on the recent record and even less on the Holocene.
Given our growing understanding of human impact on the
global environment and climate system, one of the primary
goals of the new Summit cores from the Greenland Ice Core
Project (GRIP) and the Greenland Ice Sheet Project 2
(GISP2) was to take fuller advantage of the rich density of
information available in the cores. In particular, there was an
emphasis on determining how the isotopic signal records the
recent climatic conditions of central Greenland and how those
climate conditions can be related to the climate of the North
Atlantic region. Despite the great potential for using isotopic
data from ice cores to look at climate changes of the past few
centuries, these data have been largely ignored and/or dis-
missed in studies of recent climate change. This is due in part
to a lack of high-resolution isotopic data from the upper parts
of cores and in part to a lack of emphasis on understanding the
nature of the isotopic signal and what it records. Recently,
several papers have addressed this issue, using data from the
new GISP2 and GRIP cores in the Summit region as well as
other isotopic data, mostly collected and analyzed by the Dan-
ish and Canadian groups, which have recently become avail-
able for public distribution via the World Data Centers A for
Paleoclimatology and Glaciology (Boulder, Colorado). In this
paper we will review those efforts, which uniformly point to-
ward the conclusion that annually resolved isotopic data from
Greenland ice cores do contain useful climatic information.
We will then take a first look at the climate signals found in the
26,425

26,426 WHITE ET AL.: CLIMATE FROM ISOTOPES IN GREENLAND SNOW
stacked isotopic record from the Summit region. A total of six
cores in the Summit region were drilled, sampled, and mea-
sured with sufficient temporal detail to calculate annual isoto-
pic values. We have for the first time the capability to stack
isotopic records and thus to greatly decrease the isotopic noise
which is present in a single record, focusing attention on the
common signal present in a suite of cores. The stacked record
is described in a companion paper by Johnsen et al. [this issue].
Here we will compare this record to records of climate change
in the region in order to determine what climatic signals are
present in the isotopic composition of Greenland snow from
the Summit region.
2. Stable Isotope Ratios of Greenland Snow
and Regional North Atlantic Climate:
An Overview of Recent Results
Several recent studies have linked the isotopic composition
of snow (•80/•60 and/or D/H, expressed as 8•80 and 8D) in
the Summit area with climatic indicators or climate proxies in
the North Atlantic region. These include the North Atlantic
Oscillation (NAO), which is the atmospheric pressure oscilla-
tion between Iceland and the Azores [Walker, 1924; van Loon
and Rogers, 1978; Moses et al., 1987; Rogers, 1984; Barlow et al.,
1993; White et al., 1996], regional Greenland temperatures
[Fisher et al., 1996], the temperature seesaw, which is an op-
position in atmospheric temperatures between western Green-
land (Jakobshaven) and western Scandinavia (Oslo) [van Loon
and Rogers, 1978; Barlow et al., 1993], and solar activity [Stuiver
et al., 1995]. The results of these studies are reviewed below.
Our focus here will be on these newer studies as they all
examine data from the Summit area. We will later use the
relationships found in these studies between these climatic
parameters and the isotopic record of central Greenland as a
beginning point in examining the climate signals in the stacked
isotopic record from Summit.
The North Atlantic Oscillation is a unifying atmospheric
feature with associated variability in sea surface temperature
(SST) and land surface temperatures in the North Atlantic
region. The NAO denotes a sea level pressure contrast be-
tween the Icelandic Low and Azores High, specifically the
tendency of these two centers of action to strengthen or
weaken together [Walker, 1924; van Loon and Rogers, 1978;
Moses et al., 1987]. The NAO index is defined as the normal-
ized monthly mean sea level pressure difference between
Akureyri, Iceland, and Ponta Delgada, Azores [van Loon and
Rogers, 1978; Rogers, 1984]. Sea level pressure difference in the
North Atlantic is strongest in the winter, and generally the
NAO is discussed in terms of its winter character.
Investigations of the NAO by van Loon and Rogers [1978],
Rogers and van Loon [1979], Lamb [1977], Kelly et al. [1987],
and Moses et al. [1987] indicate two distinctly different atmo-
spheric and oceanic temperature regimes for the two extreme
modes of the NAO. The temperature seesaw, or tendency for
air temperatures in western Greenland to be warmer when air
temperatures in western Scandinavia are cooler (and vice ver-
sa), describes this opposition of temperatures in the region.
Intensification of the "normal" mode of the NAO (deep Ice-
landic Low, strengthened Azores High) has associations with
the Greenland below (GB; Greenland colder) mode of the
temperature seesaw as well as with stronger westerly winds and
higher than normal SSTs for large parts of the North Atlantic
Drift (Figure la). Stronger zonal westerlies are also associated
with warmer temperatures in England and northern Europe.
Intensification of the "reverse" mode of the NAO has associ-
ations with the Greenland above (GA; Greenland warmer)
mode of the temperature seesaw, as well as with weaker west-
erlies, stronger meridional winds, and lower SSTs in parts of
the North Atlantic Drift (Figure lb). Stronger meridional
winds are also associated with warmer temperatures along the
west Greenland coast.
The link between stable isotope ratios from snow in central
Greenland and the NAO was originally established in the
GISP2 core [Barlow et al., 1993] through association with the
seesaw in winter temperatures between Jakobshaven, Green-
land, and Oslo, Norway. Using the high-resolution isotopic
record, which contains at least eight samples per annual layer,
Barlow et al. compared the isotopic values of snow averaged
annually as well as the lowest isotopic values (isotope "win-
ters") and the highest values (isotopic "summers") with the
temperature seesaw. The focus was on the strong GA and GB
years taken from the winter seesaw values of van Loon and
Rogers [1978] for the years 1840-1970. Within this time period,
there were 23 GA winters and 26 GB winters. A one-tailed
t-test showed high statistical significance for annual and winter
as well as summer signals. The isotopic signal from the GISP2
site responds in agreement with the west Greenland (Jakob-
shavn) side of the temperature seesaw. It should be noted that
the temperature seesaw is not well defined in coastal temper-
ature stations on east Greenland. This suggests that while
there is some regional coherence in the coastal Greenland
temperatures, part of the variability in atmospheric tempera-
tures in Greenland is different from the western to the eastern
sides of the ice sheet. An investigation of storm tracks, cyclo-
genesis, atmospheric circulation patterns, and automatic
weather station (AWS) records suggests that precipitation ar-
rives in central Greenland primarily from both the southeast
and southwest/west [Barlow, 1994; Barlow et al., this issue].
This observation suggests that the isotopic composition of
snow should respond to both the average coastal temperatures
and the temperature pattern described by the temperature
seesaw, a suggestion that will be supported by the results of the
multiple linear regression analysis of the stacked isotope
record described in the second part of this paper.
In a different approach to relating the stable isotopes in the
GISP2 core to climate change, White et al. [1996] examined the
power spectrum of the annually averaged 8D values and com-
pared the periodicities found in the isotopic record with oscil-
lations found in records of climate change. The isotopic record
at GISP2 exhibits many statistically significant oscillations.
White et al. identified several which can also be found in other
annually resolved isotopic records from Greenland, including
sites in southern Greenland (Dye 3) and northern Greenland
(Camp Century). These periods, in years, are 4.5, 6.3, 7.5, 9.8,
12.2, and 16. These oscillations were filtered from the isotopic
time series and then plotted against similarly filtered oscilla-
tions from (1) the NAO, which has its strongest oscillation at
7.6 years, (2) sunspots, with a strong oscillation at 11-12 years,
and (3) the 8180 record from corals, which has a strong oscil-
lation at 4.6 years and which is a proxy of the E1 Nifio-
Southern Oscillation (ENSO). The results of this study found
no statistical coherence, or similarity in the temporal pattern of
the amplitudes, for the isotopic signal versus ENSO, either for
the pressure indices or isotopic values from corals.
There was also no coherence between the l 1-year cycle of
sunspot numbers and the l 1-year cycle found in the GISP2

WHITE ET AL.: CLIMATE FROM ISOTOPES IN GREENLAND SNOW 26,427
a
0 ø,
30'
85'
70'
Higher
$ST
55' W
80;
L
Zonal
winds
40' W
b
H
25' W
10'W
5'E
5O:
winds
0 ø,
100'
Lower L
SST
85'
70'
55' W 40' W 25' W
10'W
5'E
Figure 1. (a) Diagram of Greenland below (GB) mode of the temperature seesaw. In this end-member,
Jakobshavn, Greenland, is relatively cold (marked by a minus sign) and Oslo, Norway, is relatively warm
(marked by a plus sign). Accompanying oceanic and atmospheric phenomena, all associated with extreme
normal mode of the NAO, are also noted: zonal winds with lower pressure north and higher pressure south
and higher sea surface temperatures in the western North Atlantic. The ice-core sites for GRIP and GISP2
are marked (Summit). The diagram is a compilation of observations of van Loon and Rogers [1978], Rogers and
van Loon [1979],Lamb [1977],Kelly et al. [1987], and Moses et al. [1987]. (b) As in Figure la, but for Greenland
above (GA) mode of the temperature seesaw (extreme reverse mode of the NAO).
isotopic record. Comparison of these two time series filtered to
isolate the 11-year component showed a slight correspondence,
as the strongest sunspot minima tended to occur in phase with
the strongest isotope minima. This correspondence was not
compelling evidence, however, that isotopes and sunspots are
linked. A different conclusion was reached by Stuiver et al.
[1995], who compared the GISP2 isotopic record with sunspots
for much of the Holocene. Their conclusion was that sunspots
and isotopes did indeed appear to show common variance over
this longer time period. Stuiver et al. also noted that volcanic

26,428 WHITE ET AL.: CLIMATE FROM ISOTOPES IN GREENLAND SNOW
Band-pass Filtered Components of the GISP2 •SD and the Winter NAO Indices
0
•-2
-4
-8
1880
-4
-2
-1•c
0
- 3
1900 1920 1940 1960 1980
Year
Band-pass Filtered Components of GISP2 •SD and the Winter NAO Reconstruction
-4
m 0 •'
-4 2
3
-8 4
1700 1750 1800 1850 1900 1950 2000
Figure 2. (a) Comparison of time series of/SD values from
the GISP2 ice core (thin line) and winter NAO indices (thicker
line) which have been band-pass filtered at 7.5 years to isolate
this oscillation in both records [from White et al. 1996]. In the
isotope data this is one of many significant oscillations. In the
NAO data this oscillation is significant and is the strongest in
the power spectrum. Note that both the phase and amplitude
of the two time series are very similar, implying that they are
responding to the same forcing or that this oscillation in the
isotope record is forced by the NAO oscillation. (b) As in
Figure 2a, except the winter NAO indices are inferred from
tree ring indices [Cook et al., 1997]. The match for these two
series is again excellent in the 1900s, but both the phasing and
particularly the amplitude deviate in the previous 2 centuries.
The implications of this are discussed in the text.
events appear to have an impact on the isotopic record, with
evidence of lower/5•80 (cooling) corresponding with volcanic
eruptions. They separated the volcanic events by size using
indices of explosivity and showed that larger eruptions tended
to be associated with larger/5•80 drops.
White et al. [1996] did find strong statistical coherence be-
tween the 7.6-year oscillations in the isotopic and NAO
records. In addition, the temporal patterns of these oscilla-
tions, when filtered from the individual records, match well for
the past 100 years. This is shown in Figure 2a. One drawback
of comparing the isotope values with NAO indices is that the
length of the NAO record is relatively short. In order to extend
the NAO record, a record of winter NAO indices derived from
tree rings [Cook et al., 1997] was also filtered for the 7.6-year
oscillation and then compared with the 7.6-year oscillation
filtered from the isotope time series. While all three filtered
records were very similar for the period 1880 to the present,
the correspondence between the tree ring NAO proxy and the
isotope series was not good between 1700 and 1880. This is
shown in Figure 2b. White and coworkers speculated that this
finding could mean that the NAO had a different behavior
prior to 1880, at least in the nature of the oscillations in the
indices, and that this difference could be driven by a different
climate mode during the Little Ice Age or by anthropogenic
influences in climate which began to manifest themselves in the
late 1800s. Of course, the result could also mean that one or
both of the climate proxies did not track the 7.6-year oscillation
in the NAO as well prior to 1880 for reasons having to do with
the proxy record and not the climate system. Nonetheless, the
apparent difference in behavior between 1700-1880 and 1880
to the present in the isotopic record and the tree ring NAO
record does raise some important issues for this study. First, it
reinforces the importance of using long records of climate
change to establish a baseline behavior in the climate system,
even if they are proxy records with the accompanying caveats
in interpretation, and second, it raises the point that calibrating
proxy records with historical observations of climate carries
some risk that uniformitarianism may not apply and thus the
proxy may not be correctly interpreted beyond the period of
historical observations.
One of the most exhaustive studies to date of the climate
information in stable isotope ratios in Greenland ice cores is
that of Fisher et al. [1996]. In this study, isotope records from
about 20 ice cores were used, each with isotopes measured at
subannual (>8 samples per year) resolution. Regional chro-
nologies of isotope ratios covering the last few centuries were
constructed for southern Greenland, central west Greenland,
central east Greenland, and northern Greenland, as well as for
the Canadian island sites Aggasiz, Ellesmere, and Devon.
For each region, isotope records from several individual
cores were stacked in order to reduce noise. Fisher et al. [1996]
discuss in detail the issue of noise in the isotopic times series
from individual cores. Noise in this sense is defined as isotopic
variability due to postdepositional processes which can alter
the original isotopic signal in the snow. These processes in-
clude unevenness in drifting or sastrugi, wind scouring, sum-
mer melting and penetration of the melt into the lower layers,
and vapor diffusion, which redistributes the isotopic gradients
occurring naturally due to seasonal changes in the isotopic
composition of snow.
The signal to noise ratio (S/N = (signal variance)/(noise
variance)) for a single isotopic profile in Greenland varies with
accumulation and latitude [Fisher et al., 1985]. For Greenland,
S/N appears to be smallest in the Summit area. The frequency
distribution of both the noise and signal variances in the ice
cores depends on the variable. For example, noise in snow
accumulation time series is concentrated in the higher frequen-
cies. Such noise can be reduced in a single time series by
averaging over relatively short time steps. For isotopic time
series, however, vapor diffusion tends to smooth out the high-
er-frequency variability and transfer it to the lower frequen-
cies, reddening the spectrum. This means that longer averaging
times, of the order of a decade or more, are needed to smooth
out the noise in individual isotopic time series. The necessity
for long averaging times has been observed when comparing
isotopic records from Greenland, although such averaging is
also required when cores are separated by large distances over
which climate is not correlated on the subdecade timescale
[e.g., Dansgaard et al., 1975].

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    [...]


Journal ArticleDOI
Abstract: The 3-km-long Greenland Ice Sheet Project 2 (GISP2) ice core presents a 100,000 +- year detailed oxygen isotope profile covering almost a full glacial-interglacial cycle. Measuranents of isotopic fluctuations in snow, frost, and atmospheric water vapor samples collected during summer field seasons (up to 20%0) are compatible with the large and abrupt 80/160 changes observed in accumulated tim. Snow pit 1580 profiles from the GISP2 summit area, however, show rapid smoothing of the 180/160 signal near the surface. Beyond about 2-m depth the smoothedi5180 signal is fairly well preserved and can be interpreted in terms of average local weather conditions and climate. The longer climate fluctuations also have regional and often global significance. In the older part of the record, corresponding to marine isotope stages (MIS) 5a to 5d, the effect of orbital climate forcing via the 19- and 23-kyr precession cycles and the 41-kyr obliquity cycle is obvious. From the end ofMIS 5a, at about 75,000 years B.P., till the end of the glacial at the Younger Dryas-Preboreal transition, at 11,650 years B.P., the O180/160 record shows frequent, rapid switches between intermediate interstadial and low stadial values. Fourier spectra of the oscillations that are superimposed on the orbitally induced changes contain a strong periodicity at 1.5 kyr, a broad peak at 4.0 kyr, and additional shorter periods. Detailed comparison of the GISP2 180/160 record with the Vostok, Antarctica, 15D record; Pacific Ocean foraminiferal 180/160; Grande Pile, France, tree pollen; and insolation indicates that a counterpart to many of the rapid 180/160 fluctuations of GISP2 can be found in the other records, and that the GISP2 isotopic changes clearly are the local expression of climate changes of worldwide extent. Correlation of events on the independent GISP2 and SPECMAP time scales for the interval 10,000-50,000 years B.P. shows excellent chronometric agreement, except possibly for the event labeled 3.1. The glacial to interglacial transition evidently started simultaneously in the Arctic and the Antarctic, but its development and its expression in Greenland isotopes was later suppressed by the influence of meltwater, especially from the Barents Sea ice sheet, on deep water formation and ocean circulation. Meltwaters from different ice sheets bordering the North Atlantic also influenced ocean circulation during the Bolling-Allerod interstadial complex and the Younger Dryas and led to a distinct development of European climate and Greenland 180/160 values. The Holocene interval with long-term stable mean isotopic values contains several fluauations with periods from years to millennia. Dominant is a 6.3-year oscillation with amplitude up to 3 to 4%0. Periodicities of 11 and 210 years, also found in the solar-modulated records of the cosmogenic isotopes 1oBe and 14C, suggest solar processes as the cause of these cycles. Depression of180/160 values (cooling) by volcanic eruptions is observed in stacked GISP21580 records, but the effect is small and not likely to trigger major climate changes.

862 citations


References
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Journal ArticleDOI
01 Nov 1964-Tellus A
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

6,602 citations


Journal ArticleDOI
01 Dec 1993-Nature
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.

1,835 citations


Journal ArticleDOI
Abstract: 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. High-resolution annual 18O/16O results were obtained for most of the current millennium (A.D. 818-1985) and record the Medieval Warm Period, the Little Ice Age, and a distinct 11-yr 18O/16O cycle. Volcanic aerosols depress central Greenland annual temperature (∼1.5°C maximally) and annual 18O/16O for about 4 yr after each major eruptive event. On a bidecadal to millennial time scale, the contribution of solar variability to Holocene Greenlandic temperature change is ∼0.4°C. The role of thermohaline circulation change on climate, problematic during the Holocene, is more distinct for the 16,500-10,000 cal yr B.P. interval. (Analogous to 14C age calibration terminology, we express time in calibrated (cal) yr B.P. (A.D. 1950 = 0 cal yr B.P.)). The Oldest Dryas/Bolling/Older Dryas/Allerod/Younger Dryas sequence appears in great detail. Bidecadal variance in 18O/16O, but not necessarily in temperature, is enhanced during the last phase of lateglacial time and the Younger Dryas interval, suggesting switches of air mass transport between jet stream branches. The branched system is nearly instantaneously replaced at the beginning of the Bolling and Holocene (at ∼14,670 and ∼11,650 cal yr B.P., respectively) by an atmospheric circulation system in which 18O/16O and annual accumulation initially track each other closely. Thermodynamic considerations of the accumulation rate-temperature relationship can be used to evaluate the 18 O/16O-temperature relationship. The GISP2 ice-layer-count years of major GISP2 climate transitions also support the use of coral 14C ages for age calibration.

915 citations


Journal ArticleDOI
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%...

888 citations


Journal ArticleDOI
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...

649 citations