Three-Dimensional Water and Carbon Cycle Modeling at High Spatial-Temporal Resolutions

• Main Author: Liao, Chang
• Other Authors: Zhuang, Qianlai
• Format: Text
• Language: English
• Published: Purdue University 2017
• Subjects: Ecology|Geophysics|Hydrologic sciences; glaciers; permafrost; Alaska
• Online Access: https://docs.lib.purdue.edu/dissertations/AAI10269536

Terrestrial ecosystems in cryosphere are very sensitive to the global climate change due to the presence of snow covers, mountain glaciers and permafrost, especially when the increase in near surface air temperature is almost twice as large as the global average. However, few studies have investigated the water and carbon cycle dynamics using three-dimensional modeling approach process-based hydrological and biogeochemistry modeling approach. In this dissertation, I used a 3D modeling approach at high spatial-temporal resolutions to investigate the water and carbon cycle dynamics for the Tanana Flats Basin in interior Alaska with emphases on snow dynamics, permafrost distribution and dissolved organic carbon dynamics. The results have shown that: (1) total stream discharge from the Tanana Flats Basin has decreased by 4.3 × 10-3 km3 yr-1 in recent decades. Both snowpack water equivalent (SWE) and snowmelt have decreased substantially. The decreasing trends are even more significant at higher elevation areas. The timing of snowmelt onset and ending has shifted by 2 (earlier) and 5 (later) days per decade, respectively; (2) groundwater movements are influenced significantly by permafrost that groundwater flow in permafrost-free zones contributes 44% and $83% to the horizontal and vertical flow, even though they cover only 39% of the study area. The fast storage renewal rates in the active layer are indicative of the importance of the active layer. This layer contributes 10% and 80% to the total horizontal and vertical groundwater flow although it comprises only 0.1% of the total volume; (3) vegetation dynamics have significant impacts on ecosystem productivity. A 30% decrease in total coverage area of woody savanna has caused a nearly 36% decrease in corresponding annual gross primary production (GPP) budget. The decrease in GPP also led to a transition from a carbon sink to a source; (4) lateral flow has significant impacts on net ecosystem production through its influences on soil moisture. Lateral flow also ...