Examination of Surface Temperature Modification by Open-Top Chambers along Moisture and Latitudinal Gradients in Arctic Alaska Using Thermal Infrared Photography

Nathan Healey,Steven Oberbauer,Robert Hollister

doi:10.3390/rs8010054

Abstract

Passive warming manipulation methodologies, such as open-top chambers (OTCs), are a meaningful approach for interpretation of impacts of climate change on the Arctic tundra biome. The magnitude of OTC warming has been studied extensively, revealing an average plot-level warming of air temperature that ranges between 1 and 3 °C as measured by shielded resistive sensors or thermocouples. Studies have also shown that the amount of OTC warming depends in part on location climate, vegetation, and soil properties. While digital infrared thermometers have been employed in a few comparisons, most of the focus of the effectiveness of OTC warming has been on air or soil temperature rather than tissue or surface temperatures, which directly translate to metabolism. Here we used thermal infrared (TIR) photography to quantify tissue and surface temperatures and their spatial variability at a previously unavailable resolution (3–6 mm2). We analyzed plots at three locations that are part of the International Tundra Experiment (ITEX)-Arctic Observing Network (AON-ITEX) network along both moisture and latitudinal gradients spanning from the High Arctic (Barrow, AK, USA) to the Low Arctic (Toolik Lake, AK, USA). Our results show a range of OTC surface warming from 2.65 to 1.27 °C (31%–10%) at our three sites. The magnitude of surface warming detected by TIR imagery in this study was comparable to increases in air temperatures previously reported for these sites. However, the thermal images revealed wide ranges of surface temperatures within the OTCs, with some surfaces well above ambient unevenly distributed within the plots under sunny conditions. We note that analyzing radiometric temperature may be an alternative for future studies that examine data acquired at the same time of day from sites that are in close geographic proximity to avoid the requirement of emissivity or atmospheric correction for validation of results. We foresee future studies using TIR photography to describe species-level thermodynamics that could prove highly valuable toward a better understanding of species-specific responses to climate change in the Arctic.

Highlights

Understanding the impacts of climate change on Arctic vegetation is a key requirement for prediction of how Arctic ecosystems will respond to future conditions [1]
This study reports on the use of advanced thermal infrared imagery to analyze the peak growing season temperature patterns within open-top chambers (OTCs), the passive warming devices commonly used for simulation of future temperature regimes in Arctic, Antarctic, and alpine communities
We selected long-term monitoring sites spanning latitudinal and moisture gradients where OTCs have been in place every growing season since the mid 1990s

Summary

Introduction

Understanding the impacts of climate change on Arctic vegetation is a key requirement for prediction of how Arctic ecosystems will respond to future conditions [1]. Previous warming studies using OTCs have been directed toward analyzing specific species responses [8], radiation dynamics [9], plant phenology [10], snow regime shifts [11], and trace gas exchange [12,13] to name a few. Meta-analyses of many sites combined have quantified the impacts of passive warming treatments on tundra vegetation and indicate a warming climate in high latitudes and high elevations is changing plant communities and ecosystem function [14,15]. A key variable in the interpretation of the treatment responses is the effectiveness of the OTC experimental warming within the different climate regimes, vegetation types, and soil microclimates of the tundra biome

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Conclusion