ACC29-01

Room:301A

Time:May 26 14:15-14:30

Inconsistent relations among water stable isotope in Antarctic snow under different accumulation environments
HOSHINA, Yu1∗ ; FUJITA, Koji1 ; IIZUKA, Yoshinori2 ; MOTOYAMA, Hideaki3
1

Nagoya University, 2 Institute of Low Temperature Science, Hokkaido University, 3 National Institute of Polar Research

Water stable isotopes and major soluble ions are important for reconstructing paleo-environment and atmosphere circulation.
It is also known that ion and isotope signals are modified after deposition if firn or ice core samples are analyzed at high temporal
resolution such as seasonal scale.
We compared oxygen isotope, major ions and accumulation rate in shallow ice cores and snow pits from Antarctica with highly
temporal resolution data. We showed seasonal cycle of oxygen isotope and major ions were surely preserved at sites over thethreshold of accumulation rate with calm wind condition. In order to analyze the samples widely collected from east and west
Antarctica, we calculated correlation coefficients of annually averaged major ions to oxygen isotope and then compare with accumulation rate among which the accumulation rate highly correlates. The correlations of most ions change from no correlation
to negative one with decrease of accumulation rate. The negative correlations in inland Antarctica could be formed by inconstantaccumulation due to low but larger inter-annual variability. The relations among major ions and oxygen isotope may not be thosereflecting climatic footprint but be formed as a unique signal in the extremely arid environment.

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ACC29-02

Room:301A

Time:May 26 14:30-14:45

Estimation of the age-depth relationship of Dome Fuji Ice Core using a sequential Bayesian
approach
NAKANO, Shin’ya1∗ ; SUZUKI, Kazue1 ; KAWAMURA, Kenji2 ; PARRENIN, Frederic3 ; HIGUCHI, Tomoyuki1
1

The Institute of Statistical Mathematics, 2 National Institute of Polar Research, 3 Laboratoire de Glaciologie et Geophysique del’Environnement
We have developed a method for estimating the age as a function of depth in Domu Fuji Ice Core and evaluating its uncertainty.
The age–depth relationship is mainly determined by the accumulation of snow at the site of the ice core and the thinning process
due to the horizontal stretching and vertical compression of the ice layer. However, since neither the accumulation process nor
the thinning process are fully understood, it is essential to incorporate observational information into a model that describes theaccumulation and thinning processes. In the proposed technique, the age as a function of depth is estimated from age markers
and delta-O-18 data. The estimation is achieved using the particle Markov chain Monte Carlo method, in which the sequential
Monte Carlo method is combined with the Markov chain Monte Carlo method. The performance of the proposed technique isdemonstrated by applying it to ice core data from Dome Fuji in Antarctica.
Keywords: ice core, dating method, Bayesian estimation

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ACC29-03

Room:301A

Time:May 26 14:45-15:00

Volcanic synchronization of Dome Fuji and Dome C Antarctic deep ice cores over the
past 216 kyr
FUJITA, Shuji1∗ ; PARRENIN, F.2 ; SEVERI, M.3 ; MOTOYAMA, H.1 ; WOLFF, E.4
1

National Institute of Polar Research, 2 CNRS, LGGE, F-38041 Grenoble, France, 3 Department of Chemistry, University of Florence, Florence, Italy, 4 Department of Earth Sciences, University of Cambridge, UK
Two deep ice cores, Dome Fuji (DF) and EPICA Dome C (EDC), drilled at remote dome summits in Antarctica, were synchronized to better understand their chronology. A total of 1401 volcanic tie points were identified covering the past 216 kyr.
DFO2006, the chronology for the DF core characterized by strong constraining by the O2 /N2 age markers, was compared with
AICC2012, the chronology for 5 cores including the EDC core, and characterized by glaciological approaches combining ice
flow modelling with various age markers. The age gaps between the two chronologies are within 2 kyr, except at Marine Isotope
Stage (MIS) 5. DFO2006 gives ages older than AICC2012, with peak values of the gap of 4.5 kyr and 3.1 kyr at MIS 5d and MIS
5b, respectively. Accordingly, ratios of duration DFO2006/AICC2012 are 85% at a period from the late stage of MIS 6 to MIS 5d
and 114% at a period from MIS 5d to 5b. We then compared the DFO2006 with another chronology of the DF core, DFGT2006,
characterized by glaciological approaches with weaker constraining by age markers. Features of the DFO2006/DFGT2006 age
gaps are very similar to those of the DFO2006/AICC2012 age gaps. This fact lead us to hypothesize that a cause of the systematic
DFO2006/AICC2012 age gaps at MIS 5 are associated with differences in the dating approaches. Besides, ages of speleothem
records from China agreed well with DFO2006 at MIS 5c and 5d but not at MIS 5b. Thus, we hypothesize at least at MIS 5c and5d, major sources of the gaps are systematic errors in surface mass balance estimation in the glaciological approach. Compatibility of the age markers should be carefully assessed in future.
Keywords: ice core, dating, Milankovitch, Dome Fuji, Dome C, Antarctica

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ACC29-04

Room:301A

Time:May 26 15:00-15:15

Millennial scale site and source temperatures variability in Antarctica over the past 700,000
years
UEMURA, Ryu1∗ ; MOTOYAMA, Hideaki2 ; DOME FUJI ICE CORE RESEARCH GROUP, .2
1

University of the Ryukyus, 2 National Institute of Polar Research

Deuterium-excess (d-excess = δD ? 8δ 18 O) provides the information on the ocean surface conditions in the moisture sourcefor polar precipitation. We show a new d-excess record from the 3,035m-depth Dome Fuji ice core (DF2), which was obtainedat the Dome Fuji station (77?19S, 39?42S, 3,810m a.s.l.). The new part of DF2 core (2400m to 3034m depth) extends back to
700ky BP with fine time-resolution. The ∆Tsite and ∆Tsource histories were reconstructed based on the d-excess data.
Keywords: ice core, oxygen isotope, hydrogen isotope, d-excess, Antarctica

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ACC29-05

Room:301A

Time:May 26 15:15-15:30

Glacial abrupt climate changes and thermal threshold of the Atlantic meridional overturning circulation
OKA, Akira1∗ ; ABE-OUCHI, Ayako1 ; YOKOYAMA, Yusuke1 ; KAWAMURA, Kenji2 ; HASUMI, Hiroyasu1
1

Atmosphere and Ocean Research Institute, University of Tokyo, 2 National Institute of Polar Research

Abrupt climate changes known as Dansgaard-Oeschger events (DO events) took place frequently in glacial periods. Many
geological evidences support the idea that changes of the Atlantic meridional overturning circulation (AMOC) are related tothese events, but question on what triggers the AMOC changes remains unsolved. Although the most of studies have regarded
freshwater flux from melting ice sheet as a cause of the AMOC changes, we recently identified the existence of the thermal
threshold of the AMOC during glacial climate. Here, from the results of climate model simulations about the glacial AMOC,
we report that the thermal threshold of the AMOC can be a triggering mechanism of DO events. We investigated the structure of
the thermal threshold in glacial climate by conducting ocean general circulation model simulations under various thermal conditions in which degrees of sea surface cooling are systematically changed separately or simultaneously in northern and southernhemispheres. The results suggest that the threshold is located near the condition in which the climate is slightly warmer than thecoldest glacial conditions. We also found that the amplitude of AMOC changes in crossing this threshold depends on thermal
conditions in northern and southern hemispheres. This amplitude becomes the largest when the southern hemisphere is slightly
warmer than the coldest glacial conditions. It is also demonstrated that gradual warming in the southern hemisphere from thecolder glacial climate leads to crossing the threshold and can cause very large strengthening of AMOC. Therefore, the thermal
threshold could be a triggering mechanism of DO events accompanying the warming of southern hemisphere before their abrupt
warming in northern hemisphere.
Keywords: Atlantic meridional ocean circulation, Dansgaard-Oeshger events, Abrupt climate changes, Climate model

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ACC29-06

Room:301A

Time:May 26 15:30-15:45

The influence of glacial ice sheet on Atlantic meridional overturning circulation throughatmospheric circulation change
SHERRIFF-TADANO, Sam1∗ ; ABE-OUCHI, Ayako1 ; YOSHIMORI, Masakazu3 ; OKA, Akira1 ; CHAN, Wing-le1
1
3

Atmosphere and Ocean Research Institute, University of Tokyo, 2 Japan Agency for Marine-Earth Science and Technology,
Faculty of Environmental Earth Science, Hokkaido University

Several atmosphere-ocean coupled general circulation model (AOGCM) studies suggest that glacial ice sheets exert a large
impact on the Atlantic meridional overturning circulation (AMOC). However, the process by which the ice sheets impact on the
AMOC is not yet fully understood because of the complicated nature of the AOGCMs. On the other hand, recent oceanographic
studies showed that surface wind changes play a crucial role on changes to the AMOC under glacial climate. Therefore, in thisstudy, we investigate in detail, the process by which the ice sheet modifies the AMOC through surface wind change. Moreover,recent modeling study using MIROC AOGCM showed that the effect of the glacial ice sheet on the AMOC depends on the
background climate. In their study, they suggested that a strong relation between sea ice coverage and the wind field might play
an important role. However, it is still unclear to what extent the sea ice coverage affects the surface wind change induced by theglacial ice sheet. Therefore, we will also explore the effect of the sea ice distribution on the ice sheet induced wind change. Herewe conduct numerical experiments using an atmospheric general circulation model (AGCM) and an ocean general circulation
model (OGCM) separately. Our method consists of 2 steps. First, from AGCM experiments, we evaluate the effect of glacial
ice sheets on the surface wind. Second, from OGCM experiments, we evaluate the influence of the wind stress change on the
AMOC by applying the surface wind change as a boundary condition, while leaving other boundary conditions (surface heat andwater fluxes) unchanged. In this way, we can evaluate the wind effect of glacial ice sheet on the AMOC. In addition, we conduct
several sensitivity experiments. Using the AGCM, we changed the sea ice distribution. Moreover, using the OGCM, we change
the surface wind gradually or apply the surface wind change only at a specific region in order to explore the wind change effectin detail.
We find that glacial ice sheets largely intensify the AMOC by surface wind change under glacial climate. Compare to otherregions, it reveals that the wind change at the North Atlantic mid-high latitude (NAMH) is a key region. There, the positive windstress curl enhances, which intensifies the salt and heat transport at NAMH surface through strengthening the gyre circulationand the Ekman upwelling. As a result, the AMOC intensifies. On the other hand, we find that this wind effect of glacial ice sheet
strongly depends on the NAMH sea ice cover, as the expansion of sea ice reduces the positive wind stress curl anomaly inducedby the glacial ice sheet. This supports the important role of the sea ice coverage on glacial ice sheet effect suggested by the study
using MIROC AOGCM.

Keywords: AMOC, surface wind, sea ice, glacial ice sheet

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ACC29-07

Room:301A

Time:May 26 15:45-16:00

Intermediate depth ice core drilling project 2015/2016 and some results of deep boreholelogging, Antarctic ice sheet
MOTOYAMA, Hideaki1∗ ; FURUSAKI, Atsushi2 ; MATOBA, Sumito8 ; SUGIYAMA, Shin8 ; TAKAHASHI, Akiyoshi3 ;TANAKA, Yoichi4 ; MIYAHARA, Morihiro5 ; TAKATA, Morimasa6 ; SAWAGAKI, Takanobu7 ; SHINBORI, Kunio8 ;MORI, Shoichi8
1

National Institute of Polar Research, 2 Asahikawa National College of Technology, 3 Geo Tecs Co. Ltd, 4 Geosystems Inc., 5 Anori
Inc., 6 Nagaoka University of Technology, 7 Faculty of Env. Earth Science Hokkaido University, 8 Institute of Low Temperature
Science, Hokkaido University
We plan the intermediate depth drill in 2015/2016 on the coastal region of Antarctic ice sheet. We decided the dry drilling for
300-500m deep. Problems are bad core quality and borehole closure.
The deep ice core drilling in depth of 3,035m was succeeded at Dome Fuji Station, Antarctica in January, 2007. It is almost
depth of the bedrock. We used butyl acetate as borehole liquid. The liquid level was approximately 120m from the surface. We
carried out borehole logging observation from surface to bottom in January 2007, 2011 and 2013. Measurement items were liquid
temperature, ice temperature, liquid pressure and borehole diameter. The resolution of temperature was 0.05 degree Celsius. We
discuss the diameter change/inclination of borehole, distribution of heat flow rate in ice sheet using the data of some years.
Keywords: ice core, Antarctic ice sheet, intermediate depth ice core drilling, borehole logging, heat flux

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ACC29-08

Room:301A

Time:May 26 16:15-16:30

Comparison of different measurement techniques of micro-particles in polar snow andice
GOTO-AZUMA, Kumiko1∗ ; HIRABAYASHI, Motohiro1 ; MOTOYAMA, Hideaki1
1

National Institute of Polar Research

Water-insoluble micro-particles in ice cores have been extensively analysed to investigate the past climatic and environmental
changes. Temporal and spatial variations of size distribution and flux have been discussed in many papers. Definition of particle
size, however, is not always straightforward. Flux of particles is calculated from particle volume, particle density and snow
accumulation rate, thus affected by the definition of particle size, which depends on the measurement technique. Comparison of
the size distribution and flux data from different measurement techniques requires caution. Here we compare the measurement
results from traditionally used three types of micro-particle analysers: (1) Coulter Multsizer 4, which directly measures volumeof each particle; (2) Klotz Abakus, which detects shading of laser light caused by each particle; and (3) Met One Model 211,
a laser scattering type particle analyser. We also show the results from a newly introduced micro-particle analyser JASCO IF200nano, which is based on image processing technique. The new analyser indicated that Abakus and Met One Model 211 gave
size distribution different from Coulter Multisizer 4 when particle shape departed greatly from spherical shape.
Our results suggest that dust particles in Antarctic Dome Fuji core have spherical shape during glacials, while they haveirregular shapes during inter-glacials. Changes in particle shape would give additional information on the past climate andenvironment. Our results also indicate that comparison of size distribution and flux data obtained with different measurement
techniques requires much more caution than previously thought.

Keywords: micro-particles, analytical techniques, polar snow and ice

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ACC29-09

Room:301A

Time:May 26 16:30-16:45

Physically based reconstruction of summer temperature from ice layers in ice cores
FUJITA, Koji1∗ ; MATOBA, Sumito2 ; TAKEUCHI, Nozomu3 ; AOKI, Teruo4
1
3

Graduate School of Environmental Studies, Nagoya University, 2 Institute of Low Temperature Science, Hokkaido University,
Graduate School of Science, Chiba University, 4 Meteorological Research InstitutePrevious studies, which have reconstructed summer temperature from ice layers in ice core, relied on approximate relationshipbetween ice layer and instrumental temperature observed nearby station. Here we demonstrate a novel method to reconstruct
summer temperature from ice layers in ice core using an energy balance model, in which heat conduction through firn andrefreezing of meltwater are taken into account. Parameters used in the model are firstly calibrated with 2-year meteorological
data observed at the SIGMA-A site, northwest Greenland. Using the ERA-Interim reanalysis dataset, we calculate amount ofrefrozen water within firn under different settings of summer temperature and annual precipitation, and then prepare a lookup
table containing summer temperature, annual precipitation, and refrozen amount. We then estimate summer mean temperaturefrom refrozen amount and annual accumulation, which are available from an ice core, by referring the lookup table. We apply
this method to three ice cores under different climates; Belukha in the Russian Altai, Aurora in the Alaska, and SIGMA-A in thenorthwest Greenland. Reconstructed summer temperatures show large inter annual variability, which is comparable to those ofobserved temperature, but show some biases, which are affected by albedo setting. This method allows us to estimate summer
temperature using information solely available in ice core without making any approximate relationship between temperatureand ice layer.

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ACC29-10

Room:301A

Time:May 26 16:45-17:00

Ice core records of organic aerosol tracers over the past 450 years
SEKI, Osamu1∗ ; KAWAMURA, Kimitaka1 ; SHIRAIWA, Takayuki1
1Institute of Low Temperature Science, Hokkaido University

Carbonaceous aerosols, which include a mix of light absorbing and light-scattering components, influence the global climate
via direct and indirect effects on radiative balance. However, the natural variability and factors controlling the emissions, transport and role in the climate system of carbonaceous aerosols are highly uncertain both for the past and future. Here we analyzed
organic molecule tracers in ice-cores collected from Greenland and Kamchatka Peninsula over the past 450 years. Newly generated and previously published organic tracer records (Kawamura et al., 1996, 2012) were derived from Greenland Site-J and theKamchatka Ushkovsky ice-cores. Concentrations of specific organic tracers: soil bacteria derived long-chain dicarboxylic acids(hereafter di-acids), higher plant leaf-wax derived long-chain monocarboxylic acids (hereafter leaf-waxes), and biomass burningderived levoglucosan are applied to reconstruct changes in the deflation and transport of soil organic matter (di-acids and leafwaxes) and biomass burning products (levoglucosan and leaf-waxes). The concentrations and composition of biomass burning-,
soil bacterial- and plant wax -tracers in the two ice cores were found to correspond with Arctic and regional temperatures fromthe different parts of the world over solar modulated multi-decadal time-scales with order of magnitude decreases (increases) inabundance during the colder (warmer) phases of the Little Ice Age. Thus, our study suggests a strong link between Arctic climate
and carbonaceous aerosol loading in the high latitude.
Keywords: ice core, Greenland, Kamchatka, organic aerosol, Little Ice Age, Arctic Oscillation

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ACC29-11

Room:301A

Time:May 26 17:00-17:15

Reconstructions of past cyanobacteria flora from ice core samples on Gregoriev Glacier,Kyrgyz Tienshan
SEGAWA, Takahiro1∗ ; TAKEUCHI, Nozomu2 ; YONEZAWA, Takahiro3
1

Transdisciplinary Research Integration Center, National Institute of Polar Research, 2 Chiba University, 3 Fudan University

Analyses of ice cores have often been used as a means to reconstruct past environments. The species composition of theorganism such as microorganism in the ice cores could reflect the environmental condition at that time. Thus, organisms in
ice cores could be useful to reconstruct past environments. However, analysis of the biological contents of ice cores is still
highly limited. The ice core samples collected on Gregoriev Glacier, Kyrgyz Tienshan were melted using a device that enabled
us to obtain water only from the inner portion of the cores. Complete separation of the inner and outer cores is required to
avoid contamination microorganisms such as bacteria and fungi that can adhere to the cores during drilling and storage. We
report results of cyanobacterial species and their evolution by molecular DNA analysis collected from the ice core sample (about
8,000 and 12,500 years old). We also attempted to reconstruct the organisms and their interactions within the community andwith the environment on the sampled sites. The results implied genomic information used as an environmental marker for pastenvironmental studies.

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ACC29-12

Room:301A

Time:May 26 17:15-17:30

Reconstruction of paleo-environmental changes in the northern North Pacific region froman alpine ice core
TSUSHIMA, Akane1∗ ; MATOBA, Sumito2 ; SHIRAIWA, Takayuki2
1

Graduate School of Environmental Science, Hokkaido University, 2 Institute of Low Temperature Science, Hokkaido University

A 180.17-m ice core was drilled at Aurora Peak in the central part of the Alaska Range, Alaska, in 2008 to allow reconstructionof centennial-scale climate change in the northern North Pacific. The 10-m-depth temperature in the borehole was -2 ℃, whichcorresponded to annual mean air temperature at the drilling site. In this ice core, there were many melt-refrozen layers due tohigh temperature and/or strong insolation during summer seasons. We analyzed stable hydrogen isotopes (δD) and chemical
species in the ice core. The ice core age was determined by annual counts of δD and seasonal cycles of sodium ions, and weused reference horizons of tritium peaks in 1963 and 1964, major volcanic eruptions , and a large forest fire in 2004 as age
controls. Here, we show that the chronology of the Aurora Peak ice core from 180 m to the top corresponds to the period from1666 to the summer season of 2007, with a dating error of ±3 years. Our results suggest that temporal variations in δD andannual accumulation rates are strongly related to shifts in the Pacific Decadal Oscillation index (PDOI). The remarkable increasein annual precipitation since the 1970s has likely been the result of enhanced storm activity associated with shifts in the PDOI
during winter in the Gulf of Alaska.
Keywords: Alpine ice core, Northern North Pacific region, δD, d-excess

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ACC29-13

Room:301A

Time:May 26 17:30-17:45

Variations in oxygen and nitrogen stable isotopes in nitrate in an ice core of Tienshan
Mountains
TAKEUCHI, Nozomu1∗ ; OHTE, Nobuhito2 ; FUJITA, Koji3 ; VLADIMIR, Aizen4
1

Chiba University, 2 Kyoto University, 3 Nagoya University, 4 University of Idaho

Nitrate is one of the common soluble ions in snow and ice of glaciers and is usually supplied as aerosols derived from naturalor anthropogenic processes. Nitrogen and oxygen stable isotopes of nitrate can provide a means to determine its main source
and microbial process including nitrification and denitrification in snow and ice. In this study, we analyzed nitrogen and oxygen
stable isotopes of nitrate in selected depths of the ice core drilled from Grigoriev Ice cap in Kyrgyz Tien Shan Mountains ofCentral Asia in 2007. The ice core was 87 m from the surface to the bottom, and covered approximately 12700 years, which
was dated with radiocarbon. Mean nitrate concentration was 288 ppb in this ice core. Nitrogen isotope of nitrate showed that it
was distinctively higher in the 20th century, but lower before the 20th century, indicating that the source of nitrate changed fromnatural to anthropogenic in the 20th century. Oxygen isotope of nitrate showed that it generally varied from +70 to +80 ‰, but
was remarkably lower ranging from +30 to +60 ‰ in 1960s and 6000-7000 bp. This suggests that nitrate was mostly atmosphericorigin, but was occasionally derived from microbes on the glacier surface.

Keywords: ice core, stable isotope, nitrate, glacial microbe, central asia, tine shan mountains

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ACC29-P01

Room:Convention Hall

Time:May 26 18:15-19:30

Studies of melting ice using laser for ice drilling
SAKURAI, Toshimitsu1∗ ; CHOSROWJAN, Haik1 ; SOMEKAWA, Toshihiro1 ; FUJITA, Masayuki1 ;MOTOYAMA, Hideaki2 ; WATANABE, Okitsugu2 ; IZAWA, Yasukazu1
1

ILT, 2 NIPR

We have studied the melting properties of ice using CO2 laser at 10.6 micro-meter wavelength. At this wavelength ice strongly
absorbs and a hole is drilled along the path of the laser irradiation. The melting speed of ice has been measured at several
irradiation intensities and laser excitation angles relative to the horizontal axis. The melting speed of ice increased almost
proportionally with the increasing laser excitation intensity. For the laser excitation intensity of about 50 W/cm2 , for instance,
the melting speed was estimated to be 4 mm/s and 0.8 mm/s for snow (0.15 g/cm3 ) and ice, respectively. Experimental results
show that for elevated excitation angles melt-water accumulate in the hole adversely affecting the melting speed of ice. Though
the problem of accumulating water during the drilling into ice is necessary to take into consideration, we believe that our conceptof a fiber coupled IR laser drilling system could be employed for drilling ice sheets and glaciers.
Keywords: ice, laser, absorption, melt, drilling, ice sheet

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ACC29-P02

Room:Convention Hall

Time:May 26 18:15-19:30

State dependence of climatic instability from ice-core records over the past eight glacial
cyclesKAWAMURA, Kenji1∗ ; DOME FUJI ICE CORE PROJECT, Members1
1

National Institute of Polar Research

Climatic variability on millennial timescales with bipolar seesaw pattern during glacial period has been documented in palaeoclimatic records, but their frequencies and relationships with mean climatic state are still unclear. Here we investigate thelong-term characteristics of such variability using a new 700,000-year ice core record from Dome Fuji, East Antarctica, combined with another long Antarctic record. The 103 - to 104 -year warming events over the past eight glacial-interglacial cycles
are most frequent when Antarctic temperature is slightly below average, equivalent to an intermediate climate during glacial
periods. With the ice core data and climate modeling, we suggest that the prerequisite for the most frequent climate instability
with bipolar seesaw pattern during the late Pleistocene is not only the extent of continental ice sheets but also low CO2. North
Atlantic cooling sets high sensitivity of AMOC and climate to small perturbations such as moderate freshwater anomaly.
Keywords: Dome Fuji ice core, Abrupt climate change, Millennial-scale variability

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ACC29-P03

Room:Convention Hall

Time:May 26 18:15-19:30

Modelling the state dependency of abrupt climate change and bipolar seesaw
ABE-OUCHI, Ayako1∗ ; OHGAITO, Rumi2 ; YOSHIMORI, Masakazu3 ; OKA, Akira1 ; TAKAHASHI, Kunio2 ;KAWAMURA, Kenji4
1

AORI, Univ. of Tokyo, 2 JAMSTEC, 3 Hokkaido University, 4 National Institute of Polar Research

Millennial climate change such as D-O cycles, AIM recorded in ice cores in both Hemispheres is known to show a relatively
higher amplitude in the middle-level of a glacial cycle than in the interglacial state or severe glacial state. Although massive
discharge or melt water of Ice sheet to ocean is one of the cause thought to be responsible for the millennial climate change, thethermal response to fresh water release in North Atlantic in global models and/or the paleoclimatic data in the region far from
North Atlantic do not agree and even do not explain the dependence of the amplitude upon the level of climate state. Here we ran
several sensitivity experiments using a coupled atmosphere and ocean GCM (MIROC3.2.2) and show that the response to fresh
water release to the ocean and bipolar response is highly dependent on the background climate. The experiments were conductedwith 500 years water hosing of 0.05 to 0.1 Sv (where 1 Sv is equivalent to the water flux of 10m sea level rise in 100 years)
in the North Atlantic 50-70N in the same manner and position as CMIP/PMIP protocol under different basic states; Modern
Hosing under modern climate with the pre-industrial condition, and Glacial hosing under LGM condition (21ka as PMIP, withice sheets and lowered Greenhouse Gases). The results show largest cooling response in North Atlantic and a reasonable bipolarwarming signal as in the ice cores of Antarctica, and the dependence upon background climate is not relatively the same forthe both hemisphere. The mechanism of different responses are discussed in detail through the analysis of model experiment of
atmosphere, ocean and sea ice coupling.
Keywords: climate model, abrupt climate change

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