Talk by Sumito Matoba, Hokkaido University – Niels Bohr Institute - University of Copenhagen

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Niels Bohr Institute > Calendar > 2011 > Talk by Sumito Matoba,...

Talk by Sumito Matoba, Hokkaido University

Study on alpine ice cores in northern North Pacific Japanese now survey program at Qaanaaq region in 2011-14

0 Self-introduction
  When I was student...
1 Alpine ice cores in northern North Pacific region
Climate and environment at the northern North Pacific region are influenced by El Nino (ENSO), Arctic Oscillation (AO), Pacific Decadal Oscillation (PDO), Siberian High, Asian Dust and so on. In this region, there are limited sources of past meteorological, climatological and oeanographical data. Ice core is one of the valuable proxies in this region.
We obtained several ice cores from alpine glaciers at Kamchatka and Alaska.
1-1. Recent increase of accumulation rate in an ice core obtained from Aurora Peak, Alaska Range
  A 180-m ice core was drilled at the ice divide near Aurora Peak in Alaska Range. The ice thickness was estimated 252m by radio echo sounding. Ice core age was determined by annual counting of dD and Na+ which showed obvious seasonal cycles, and reference layers of volcanic signals and tritium.
Annual accumulation rate, which was estimated by seasonal cycle of dD, increased remarkably from 1970s to present. We assume that the increase of annual accumulation result from enhancement of cyclonic activity in winter because concentration of Na+ increased from 1970. However, any precipitation data observed at meteorological station do not show the trend of increase from 1970. I am analyzing d-ex in CIC, and trying to extract information about vapor transport and so on.
1-2. Reconstruct of deposition of Asian Dust
  The northern North Pacific Ocean is one of the HNLC (High Nutrient Low
Chlorophyll) water regions. Primary bio productivity in HNLC regions is limited by the availability of iron in seawater. Asian dust is one of the major sources which supply iron into the northern North Pacific Ocean. We reconstruct the deposition of air borne Fe into ocean with Alaskan ice core.
Annual deposition of Fe was 8.1 mg /m2 yr in 1980-2003. The variation of annual deposition of Fe is associated with the frequency of dust storm in the East Asian Continent in spring. To evaluate influence of air borne Fe to marine bio productivity, one of uncertain factors is solubility of Fe in seawater after deposition. We tested the solubility of Fe using snow cover in Sapporo and Alaskan ice core samples .The solubility of Fe in snow at Sapporo and Alaskan sample were 1.2% and 10%, respectively. It is assumed that the solubility of Fe enhanced by reaction of acid gases during the transportation from Asia to North America.
2. Snow Survey Program in Qaanaaq Region 2011-14
  Two programs, SIGMA (Snow impurity and Glacier Microbe effects on Arctic), and GRENE-Arictc (GReen Network of Excellence) are running from
2011 in Japan. The objective of SIGMA is to elucidate the quantitative contributions of snow impurities (BC, Dust etc) and glacial microbes (Cyanobacteria, Cryoconite) on the recent abrupt snow/ice melting in the Arctic. We selected Qaanaaq region as study site, and carried out a pre research at a glacier behind Qaanaaq settlement and at 1500m site of ice sheet in August 2011. And we are going to carry out (1) glaciological and spectral observations at ice sheet (1500m asl) from mid June to mid July,
(2) biological observation at Qaanaaq glacier, (3) Snow survey from 2000m to 1500m site in 2012, (4) shallow drilling at 2000m site in 2013, and (5) Hot water drilling at carving glacier in 201x.