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
1ILT, 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 glacialperiods. 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 ofatmosphere, ocean and sea ice coupling.
Keywords: climate model, abrupt climate change

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