Monitoring CH4 in high latitudes: gaps and future needs identified through the Arctic Methane and Permafrost Challenge

The rapidly warming Arctic is expected to experience significant carbon release as permafrost thaws, yet large uncertainties remain regarding both the rate  and the carbon species released (e.g. CO₂ versus CH₄). As part of the Arctic Methane and Permafrost Challenge, co-led by the European and North American Space Agencies, we present an analysis of current monitoring gaps and future needs, alongside a case study evaluating the capability of existing and future top-down observing systems (including passive and active satellites and atmospheric towers )to detect local changes in CH₄ emissions.

This presentation focuses on the top down observing systems, as well as the infrastructure and models required to support them. Currently, XCH₄ satellite observations in high latitudes lack coverage during wintertime, nighttime, overcast conditions, and over most ocean regions. While future missions such as MERLIN may alleviate some of these limitations, high-latitude-specific challenges such as large observational angles combined with darkness and snow or ice reflectance are expected to persist for most platforms. Although many years of data are already available from a wide range of observing systems, with a substantial increase anticipated in the near future, the community is not yet prepared to fully utilise these data.

First, we lack data standards that allow both direct CH₄ observations and auxiliary variables to be combined optimally, particularly across disciplinary boundaries. To address this, we propose a high-latitude data and model intercomparison experiment. A second major challenge is the sheer volume of data being produced, which will require dedicated infrastructure and enhanced modelling capabilities for effective ingestion and analysis, particularly given the current difficulties in fully utilizing TROPOMI data. Despite significant efforts, major gaps remain in ground-based observations, which are essential for the validation and calibration of satellite and airborne systems.

Translating observations into pan-Arctic methane budgets necessarily involves modelling. In this context, missing information on soil and wetland related characteristics emerges as a key limitation. In addition, the freeze-thaw cycle closely linked to microbial activity and soil moisture remains inadequately monitored. Finally, disturbances are both difficult to observe and predict, yet play a critical role in present-day and future Arctic CH₄ emissions.

Overall, we present a roadmap for the research priorities and infrastructure investments required to reliably quantify an integrated Arctic methane budget.