Day 4

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Paper title Multivariable global lake dataset for climate applications from the first phase of European Space Agency Climate Change Initiative
  1. Laura Carrea University of Reading Speaker
  2. Christopher Merchant University of Reading
  3. Stefan Simis Plymouth Marine Laboratory
  4. Xiaohan Liu Plymouth Marine Laboratory
  5. Jean-François Crétaux LEGOS
  6. Claude R. Duguay University of Waterloo
  7. Yuhao Wu H2O Geomatics Inc.
  8. Beatriz Calmettes CLS
Form of presentation Poster
  • A5. Climate
    • A5.02 The role of Earth Observation in climate services
Abstract text Lakes are a critical natural resource of significant interest to the scientific community, local to national governments, industries and the wider public. Lakes support a global heritage of biodiversity and provide key ecosystem services and they are included in the United Nations’ Sustainable Development Goals committed to water resources and the impacts of climate change. Lakes are also key indicators of local and regional watershed changes, making lakes useful for detecting Earth’s response to climate change. Specifically, lake variables are recognised by the Global Climate Observing System (GCOS) as an Essential Climate Variable (ECV) because they contribute critically to the characterization of Earth’s climate. The scientific value of lake research makes it an essential component of the United Nations Framework Convention on Climate Change (UNFCCC) and the Intergovernmental Panel on Climate Change (IPCC).

The Lakes ECV as defined by GCOS-200 include the following thematic variables:
• Lake water level, fundamental to our understanding of the balance between water inputs and water loss.
• Lake water extent, a proxy for change in glacial regions (lake expansion) and drought in many arid environments. Water extent relates to local climate for the cooling effect that water bodies provide.
• Lake surface water temperature, correlated with regional air temperatures and a proxy for mixing regimes, driving biogeochemical cycling and seasonality.
• Lake ice cover freeze-up in autumn and advancing break-up in spring are proxies for gradually changing climate patterns and seasonality.
• Lake water-leaving reflectance, a direct indicator of biogeochemical processes and habitats in the visible part of the water column (e.g., seasonal phytoplankton biomass fluctuations), and an indicator of the frequency of extreme events (peak terrestrial run-off, changing mixing conditions).
• Lake ice thickness, which provides insight into the thermodynamics of lake ice at northern latitudes in response to changes in air temperatures and on-ice snow mass.

Observing and monitoring precisely and accurately the spatial and temporal variability and trends of the lake thematic variables from local to global scale have become critical to understand the role of lakes in weather and climate, but also for a range of scientific disciplines including hydrology, limnology, biogeochemistry and geodesy. Remote sensing provides an opportunity to extend the spatio-temporal scale of lake observations.

The ESA Lakes_cci dataset presented here includes all the Lake ECV variables, except the lake ice thickness which is in development. The dataset consists of daily observations for each thematic variable over the period 1992-2021. The dataset for each of the thematic variable has been derived from multiple instruments onboard multiple satellites with the compatible algorithms and in an effort to ensure homogeneity and stability over time.

All the thematic variables are reported on a common latitude-longitude grid of about 1km resolution for 2024 lakes distributed globally and covering a wide range of hydrological and biogeochemical regimes. For each of the thematic variables, the observations are accompanied by an uncertainty estimate which makes the dataset particularly suitable for climate applications.

An overview of the thematic variable datasets, their validation, the geographical distribution of the lakes and the way to access the data dataset will be presented together with some major global trends observed in the Lakes ECV.