11
Air-Ice Interface: Polar Ice
Valérie Masson-Delmotte and Jean Jouzel
The deposition and preservation of layers of snow, year after
year, enable many climate and environmental parameters to
be recorded in the structure and composition of the ice, as
well as in its gas inclusions and impurities. This section is
devoted specifically to information on climate variables; the
composition of the atmosphere and biogeochemical cycles
are discussed in Chap. 1 of this volume and Chap. 1 of
Volume 2.
Polar ice contains records of past changes in numerous
climate variables, some specific to that particular site, such
as temperature and accumulation with others relevant to a
larger geographical scale, such as atmospheric circulation
and the monsoon regimes. In a unique way, reconstructions
of local variables, temperature and accumulation, are drawn
from physical processes. Estimates of the accumulation of
snow can be derived from the dating of ice (see volume 1,
Chap. 9), for example, from the identification of seasonal
cycles or reference horizons. Variations in accumulation
throughout the ages are also estimated from changes in
temperature in the past, through the dependent relationship
between the saturation vapor pressure in the air and temperature. This chapter focuses on the various methods used
to quantify temperature variations. We will discuss the
exploitation of freeze-back layers caused by summer melt in
some polar regions, the inversion of temperature profiles
measured in the boreholes, the analysis and modeling of the
stable isotope composition of the ice, and finally, the analysis of the isotopic composition of nitrogen and argon in the
air trapped in the ice.
Melt Index and Borehole Temperatures
Certain glaciers and ice caps from the Arctic coastal areas
form a first collection of records where the structure of the
ice allows the changes in summer temperatures to be estimated. Many of these locations are characterized by a
summer temperature that can exceed 0 °C. In this case, the
surface snow melts, percolates into the deeper colder layers
and then refreezes. Identifying the freeze-back layers in the
physical structure of the ice allows the indices of summer
melting intensity to be reconstructed. This method was used
to estimate changes in summer temperatures over time scales
of a few centuries, such as in Spitsbergen (Svalbard) or in
the Russian Arctic, and during the Holocene, in the Canadian Arctic (Koerner and Fisher 2002). In Greenland and
Western Antarctica, some low-altitude sites (Siple Dome,
Antarctica peninsula) are also characterized by the regular or
occasional occurrence of summer melting. However, the vast
majority of deep core samples taken from the Antarctica and
Greenland ice are from sites where the temperature remains
below 0 °C throughout the year and where there are no
freeze-back layers in the ice. In these cases, several methods
have been used to estimate past changes in the local
temperature.
The diffusion of heat through the structure of the ice causes
fluctuations in the vertical temperature profile, which, once
drilling operations have been completed, can be measured
with an accuracy of one thousandth of a degree in the liquid in
the drill holes. The numerical inversion of the temperature
profile allows, in principle, the large variations of past surface
temperatures to be estimated. However, this problem is poorly
constrained and requires general assumptions to be made
about the shape of the function sought. There is a broad
uncertainty associated with the temperature estimates both in
terms of amplitude and chronology. Through this method,
estimates of temperature variations over the last century, and
even over the last millennia, have been made in some sites with
high accumulation (Dahl-Jensen et al. 1999) as well as
V. Masson-Delmotte Á J. Jouzel (&)
Laboratoire des Sciences du Climat et de l’Environnement,
LSCE/IPSL, CEA-CNRS-UVSQ, Université Paris-Saclay,
91190 Gif-sur-Yvette, France
e-mail: jean.jouzel@lsce.ipsl.fr
© Springer Nature Switzerland AG 2021
G. Ramstein et al. (eds.), Paleoclimatology, Frontiers in Earth Sciences,
https://doi.org/10.1007/978-3-030-24982-3_11
145
Air-Ice Interface: Polar Ice
Valérie Masson-Delmotte and Jean Jouzel
The deposition and preservation of layers of snow, year after
year, enable many climate and environmental parameters to
be recorded in the structure and composition of the ice, as
well as in its gas inclusions and impurities. This section is
devoted specifically to information on climate variables; the
composition of the atmosphere and biogeochemical cycles
are discussed in Chap. 1 of this volume and Chap. 1 of
Volume 2.
Polar ice contains records of past changes in numerous
climate variables, some specific to that particular site, such
as temperature and accumulation with others relevant to a
larger geographical scale, such as atmospheric circulation
and the monsoon regimes. In a unique way, reconstructions
of local variables, temperature and accumulation, are drawn
from physical processes. Estimates of the accumulation of
snow can be derived from the dating of ice (see volume 1,
Chap. 9), for example, from the identification of seasonal
cycles or reference horizons. Variations in accumulation
throughout the ages are also estimated from changes in
temperature in the past, through the dependent relationship
between the saturation vapor pressure in the air and temperature. This chapter focuses on the various methods used
to quantify temperature variations. We will discuss the
exploitation of freeze-back layers caused by summer melt in
some polar regions, the inversion of temperature profiles
measured in the boreholes, the analysis and modeling of the
stable isotope composition of the ice, and finally, the analysis of the isotopic composition of nitrogen and argon in the
air trapped in the ice.
Melt Index and Borehole Temperatures
Certain glaciers and ice caps from the Arctic coastal areas
form a first collection of records where the structure of the
ice allows the changes in summer temperatures to be estimated. Many of these locations are characterized by a
summer temperature that can exceed 0 °C. In this case, the
surface snow melts, percolates into the deeper colder layers
and then refreezes. Identifying the freeze-back layers in the
physical structure of the ice allows the indices of summer
melting intensity to be reconstructed. This method was used
to estimate changes in summer temperatures over time scales
of a few centuries, such as in Spitsbergen (Svalbard) or in
the Russian Arctic, and during the Holocene, in the Canadian Arctic (Koerner and Fisher 2002). In Greenland and
Western Antarctica, some low-altitude sites (Siple Dome,
Antarctica peninsula) are also characterized by the regular or
occasional occurrence of summer melting. However, the vast
majority of deep core samples taken from the Antarctica and
Greenland ice are from sites where the temperature remains
below 0 °C throughout the year and where there are no
freeze-back layers in the ice. In these cases, several methods
have been used to estimate past changes in the local
temperature.
The diffusion of heat through the structure of the ice causes
fluctuations in the vertical temperature profile, which, once
drilling operations have been completed, can be measured
with an accuracy of one thousandth of a degree in the liquid in
the drill holes. The numerical inversion of the temperature
profile allows, in principle, the large variations of past surface
temperatures to be estimated. However, this problem is poorly
constrained and requires general assumptions to be made
about the shape of the function sought. There is a broad
uncertainty associated with the temperature estimates both in
terms of amplitude and chronology. Through this method,
estimates of temperature variations over the last century, and
even over the last millennia, have been made in some sites with
high accumulation (Dahl-Jensen et al. 1999) as well as
V. Masson-Delmotte Á J. Jouzel (&)
Laboratoire des Sciences du Climat et de l’Environnement,
LSCE/IPSL, CEA-CNRS-UVSQ, Université Paris-Saclay,
91190 Gif-sur-Yvette, France
e-mail: jean.jouzel@lsce.ipsl.fr
© Springer Nature Switzerland AG 2021
G. Ramstein et al. (eds.), Paleoclimatology, Frontiers in Earth Sciences,
https://doi.org/10.1007/978-3-030-24982-3_11
145