National Aeronautics and Space Administration

National Climate Assessment

NASA National Climate Assessment (NCA) Activities

NASA Indicators Solicitation Proposals

Development and Testing of Potential Indicators for the National Climate Assessment

Lead PI and Center: Kyle McDonald, The City College of New York
Title: Development of Integrated Land Surface Water State Indicators for Climate Assessment

The transition of the landscape between predominantly frozen and non-frozen conditions in seasonally frozen environments impacts climate, hydrological, ecological and biogeochemical processes profoundly. This abrupt transition occurs each year over roughly 50 million km2 of the Earth's terrestrial surface at high northern latitudes. Major landscape processes closely linked to freeze/thaw (FT) state include timing and spatial dynamics of seasonal snowmelt and associated soil thaw and release of nutrients in plant available form, runoff generation and flooding, ice breakup in large rivers and lakes, timing and length of vegetation growing season and associated productivity and trace gas exchange. The timing of seasonal thawing and snowmelt in spring also coincides with the onset of the growing season and influences boreal ecosystem sink activity for atmospheric CO2. Water and energy cycles are strongly linked in seasonally frozen environments.

A warming of the terrestrial summer in the Arctic correlates with a lengthening of the snow-free season due to changes in the energy fluxes. Changes snowmelt dynamics in freeze-thaw dominated basins will create powerful terrestrial amplification to warming Arctic regions.

Accurate characterization of seasonal freeze/thaw transition timing coupled with accompanying characterization of snowpack water content, surface inundation, and radiation balance give the potential for an unambiguous indication of climate change.
We propose the development of a set of climate indicators built upon remote sensing measures of surface water state variables: Landscape freeze/thaw (FT), Snow Water Equivalent (SWE), Surface inundation fraction (Fw), and radiative flux. Combined, these state variables provide unique insight into linkages and feedbacks in terrestrial energy, water and carbon cycles and allow examination to the response of the integrated system to climate drivers.

This effort will provide the first observationally-based assessment of its kind, between surface water state and climate, based on remote sensing datasets across basin to continental scales. The indicators we will derive will be determined directly from remote sensing datasets assembled under our Team's prior and on-going NASA research and coupled with datasets available from NASA archives.

We will report these variables, their seasonal and interannual variability and multi-year trends as appropriate to each indicator. Applying multivariate analysis, we will investigate and report correlations between the measures and associated variability and trends in the correlations. We will extend this effort to assess large drainage basins in the Arctic (Yukon and McKenzie Rivers), wherein local water balance fluxes will be united with riverine transport, discharge and heat flux, and validation using monitored river discharge and temperature from USGS and Canadian sources.