HR: 0800h
AN: C41A-0176    [Abstracts]
TI: Groundwater discharge and base flow variability in the Brooks Range, North Slope, Alaska
AU: * Yoshikawa, K
EM: ffky@uaf.edu
AF: Water and Environmental Research Center, University of Alaska, Fairbanks, AK 99775 United States
AU: Hinzman, L
EM: ffldh@uaf.edu
AF: Water and Environmental Research Center, University of Alaska, Fairbanks, AK 99775 United States
AU: Kane, D
EM: ffdlk@uaf.edu
AF: Water and Environmental Research Center, University of Alaska, Fairbanks, AK 99775 United States
AB: More than 30,000 liters/sec. of spring water discharges along the eastern part of foothills of the Brooks Range, North Slope, Alaska. These springs flow all year around and cover wide areas with aufeis every winter. In Arctic regions, aufeis is among the biggest temporary storage of freshwater during winter period (more than 8 months). This study examines the historical volume of the aufeis using aerial photographs and satellite imagery as well as MODIS Airborne Simulator (MAS). The energy balance of the aufeis is also an important parameter for estimating perennial aufeis formations. We estimate the Holocene ice volume of aufeis using CaCO3 deposits in the soil. Carbonate material distributions and 13C isotope enrichment signals are indicative of the area occupied by aufeis. Thermal enrichment of the 13C spring water was around 0 to -2 permil at the Hulahula River aufeis area. The 13C isotope of the area immediately outside the aufeis field is around -25 permil and is also very low in carbonate content. The analysis of in-situ soil sample for d13C complemented with remote sensing analyses reveals historic aufeis distributions. The CaCO3 deposits appears to possess a characteristic spectral signature that is evident in the 2300 and 2550 nm wavelength range (two absorption bands 2500-2550 nm and 2300-2350 nm and a band between those two at ~ 2400 nm (2375-2425nm ). The aufeis area was not much greater during historical times such as Little Ice Age (LIA) or Last Glacial Maximum(LGM). However, some of the aufeis and springs (at least Shubik and Sadlerochit springs) survived during LGM. In case of the Sadlerochit spring, the total winter discharge (16,510,000 m3) was almost all turned to aufeis,(15,988,866 m3) preserved as ice on the tundra terrain. Questions of the spring water's ground residence time and infiltration processes are also examined in this study. We collected water from springs, wells, surface water, and precipitation samples for isotope (C, O, H, Sr) and chemical analyses. Preliminary results indicated most of the spring water might come from upper south-facing slope of the Brooks Range (limestone area). Infiltrated meteoric water percolates along the fault between Paleozoic sedimentary rocks and Permo-Triassic sedimentary rocks. A multiple-member mixing model was used to estimate the residence time of groundwater. Their residence times were around 2500 years by statistical correction model. The Kuparuk aufeis (spring) may not follow the same path as other springs. Shallow intra permafrost groundwater system (<30m) was found at Kuparuk springs around aufeis field. The Kuparuk springs residence time was 700 years. A great deal of intra permafrost water has been observed in this area (mean annual ground temperature is-7.8§C at 2003-04). Climatic warming will activate more shallow groundwater system in this area
DE: 1800 HYDROLOGY
DE: 1806 Chemistry of fresh water
DE: 1823 Frozen ground
DE: 1824 Geomorphology (1625)
DE: 1640 Remote sensing
SC: Cryosphere [C]
MN: 2004 AGU Fall Meeting