Hydrologic Responses to Degrading Permafrost

August 9-12, 2005

In the last 50 years a wide range of changes in the Arctic have been documented. Many of these changes were evident since the mid-1970s; however, it is quite likely that these changes began or were initiated early in the 20 th century, prior to extensive observational records in arctic regions. Some of the changes, like later freeze-up and earlier break-up of arctic rivers and lakes, mirror arctic-wide and even global increases in air temperature (Magnuson et al., 2000, Serreze and others, 2000). Regardless of the driving forces, however, the combined observations and documentation suggest that the arctic system may be entering a state not seen before in historic times.   The complex interplay of physical, chemical, biological and social processes interact to such a degree that it is not possible to understand future trajectories without developing more fully holistic perspectives of the complete system.  

Water must figure prominently in any such analysis because of its central and unique role in the Arctic system and water can easily serve as the integrating theme to connect disparate environmental projects into a coherent framework. Our proposed work here builds on ongoing synthesis studies by NSF-ARCSS and its Freshwater Initiative (FWI). It is a fundamental part of the climate system, biology, biogeochemistry, planetary heat balance, river discharge, change of phase between solid/liquid/gas. Water is also central to human aspects of the arctic system and, through links to the global pattern of heat and moisture circulation, the larger Earth System as well. Now well-documented rises in large river flows in Eurasia (Peterson et al. 2002) may in the century time frame play a major role in altering the contemporary patterns of ocean circulation. The associated abrupt "climate collapse" that would plunge much of the world's population and crop-growing areas into a substantially cooler period now constitutes a major societal concern (IPCC), and has been most recently brought to light (Schwartz and Randall 2004) as a national security issue. In the context of these changes, the NSF began soliciting inputs from the community at large in order to begin building a synthesis of our current knowledge of Arctic systems, with an eye toward uncovering its key dynamics, feedbacks, and potential surprises. To further advance the broader systems level of arctic research and coalesce our present knowledge, we have proposed holding a series of workshops to examine the Evolving Arctic, focusing primarily on the role of water in moderating or driving these dynamics.   The goal of each workshop will be to produce a multi-authored monograph summarizing the state-of-the-science for a specific theme.

Integrating Our Understanding

The arctic environment is undergoing marked changes in response to a changing climate.   As in all ecosystems, all components of an arctic ecosystem are intimately linked to all others.   However, unlike most other ecosystems, the Arctic remains frozen for most or all of the year. When thawing of the near-surface soil or water occurs, dramatic changes are manifest in threshold shifts in the surface energy balance, hydrological processes, and ecosystem dynamics.   The impact of such significant changes reverberates throughout the system, particularly if that area does not usually experience phase change or if the thawed period is increasing.   Another aspect of the Arctic that is partially responsible for broad scale changes affecting the entire system are the interdependent feedback loops connecting various system processes.   The complex interplay among feedbacks affects numerous processes; and each of these is often considered the domain of distinct academic disciplines.   A strong understanding of various components of the arctic system has emerged over the last two decades; however, a coherent view of the Arctic system continues to elude us.   Thematic workshops focused upon elucidating the linkages among system components will help advance the scientific community toward that system-scale understanding.   Figure 1 exemplifies the interconnectedness among system components, but it also highlights the fact that there are still some key unknowns.   Progress through ongoing research is gap-filling, but we need a mechanism to take stock of new knowledge.   Synthesis workshops are an ideal way to accomplish this.

Figure 1.   This image portrays the complex nature of how system changes interact with atmospheric, marine and terrestrial processes.   Despite its complexity, this figure does not adequately convey another important aspect of a changing climate: the dramatic threshold changes that occur when a component of the system freezes or thaws.  

Thematic Basis

Much of the understanding needed to greatly advance Arctic System Science presently exists, dispersed throughout our diverse community.   Literally hundreds of manuscripts have been crafted to explain in great detail the physical, biological and social underpinnings of arctic science.   We believe rapid advances can be achieved by gathering the appropriate experts together in the suitable field and workshop settings to share respective visions in order to build an inter-connected representation of the broader system.   The first of this series will be conducted this year, funded entirely by The University of Alaska International Arctic Research Center (IARC) through their grant from NSF. This workshop will examine the impact of degrading permafrost on hydrological processes.   Following workshops will be developed to examine other aspects of the changing arctic system, again utilizing the concept of water as an integrating theme.  

The unique character of this workshop series will be the strong emphasis on conducting group discussions in field settings.   We feel this is an appropriate venue to enhance interpersonal communication while clarifying the perceptions of workshop participants on a system level.   Our goal is to develop a sound manuscript on system interactions; in the process, all participants will further educate the group on the intricacies and dynamics of the system components.   The manuscript will be initiated during the workshop discussion sessions.   The formal outline will be defined by consensus and sub-groups will be established for individual writing assignments based upon expertise.   Compilation of the manuscript sections will be completed through web-based submission, review and revision.   We will discuss the publication outlet via e-mail discussions over the next few months.   This will streamline discussions and orient workshop participants to our purpose.   It is important that all participants agree to contribute time and effort into production of a manuscript on a reasonable schedule.  

BACKGROUND/RATIONALE

The primary control on local hydrological processes in northern regions is dictated by the presence or absence of permafrost, but it is also influenced by the thickness of the active layer and the total thickness of the underlying permafrost.   As permafrost becomes thinner or decreases in areal extent, the interaction of surface and sub-permafrost ground water processes becomes more important.   The inability of soil moisture to infiltrate to deeper groundwater zones due to ice-rich permafrost maintains very wet soils in arctic regions.   In permafrost-free areas, surface soils can be quite dry, as infiltration is not restricted; this impacts ecosystem dynamics, fire frequency and latent and sensible heat fluxes.   Other hydrologic processes impacted by degrading permafrost include increased winter stream flows, decreased summer peak flows, changes in stream water chemistry, and other fluvial geomorphological processes.   Several changes in local hydrology have already been witnessed, including drying of thermokarst ponds, increasing importance of groundwater in the local water balance, and differences in the surface energy balance.   As our climate continues to change, it becomes ever more paramount to understand and predict changes in hydrological processes.  

WORKSHOP GOALS

The purpose of this workshop is to examine how the warming climate will impact the hydrological regime.   Our primary focus will be upon the influence of permafrost.   This workshop will include local field trips around the Fairbanks area to observe and photograph evidence of permafrost degradation.   Workshop attendees will participate in field measurements of hydrological variables to quantitatively document the interdependence among the dynamic thermal and hydrological processes. This will be a 3½ day workshop.   Each morning will be spent in an informal conference-style setting where we will discuss the relationships and controls among climate, permafrost, and hydrology.   In three afternoon field trips, we will visit various sites to actively engage in field process studies.

FIELD COMPONENT: The tentative field plan is

• Afternoon Day 1 - Stable permafrost - understanding the control of cold permafrost on hydrology
• Afternoon Day 2 - Unstable permafrost - understanding the control of thawing permafrost on hydrology
• Afternoon Day 3 - Sporadic permafrost - projecting the future hydrologic regime in a markedly different permafrost environment

Management and Assessment:

This project will be a coordinated effort among a broad array of experienced scientists, but will be managed by Larry Hinzman and Charles Vörösmarty.   Logistical coordination for field-based workshops will be lead by Chris Lace of the International Arctic Research Center (IARC).   A limited number of advanced graduate students have been invited to attend.   These students were selected based upon their understanding of the arctic system and their interest in arctic science.   The tangible results of this workshop will be a high quality, peer reviewed journal publication.   Intangible results include broadening the exposure of disciplinary scientists and their graduate students, hand-to-hand outreach in local communities and industrial complexes, and outreach to the general public.