Assessment of CCI Glacier and CCI Land cover data for hydrological modeling of the Arctic ocean drainage basin David Gustafsson, Kristina Isberg, Jörgen Rosberg, Berit Arheimer SMHI CCI-CMUG Integration meeting 5, 26-28/5, 2015

WHY modelling the Arctic basin? ~ 11% of world’s river-runoff flows to the Arctic ocean (Gleick, 2000) > 50% of freshwater to the Arctic Ocean is river runoff (Barry and Serreze, 2000) 30% is Ungauged Modified from: Shiklomanov and Lammers (2009), Environ. Res. Lett.

Objectives Assess the use of ESA CCI Glacier, Land cover (and Sea level) in hydrological modelling for the Arctic: Compare CCI data with existing datasets: long term trends and seasonal variations? Can use of CCI Glacier and Land cover improve simulated river runoff to the Arctic Ocean? Is there a relation between changes in observed land cover and the simulated river runoff? WP3.9 Assessment of glacier, land cover and sea level data for hydrological modeling of the Arctic ocean drainage basin

Use of CCI data Hydrological models depend on observations of e.g. glacier area and land cover for setup, calibration and evaluation: Comparison with datasets used in the pan-arctic hydrological model Arctic-HYPE Models using CCI data (Glacier, LC) will be compared to previous model version CCI Glacier data will be used to improve the parameteri-zation of the sub-basin based glacier mass balance model. WP3.9 Assessment of glacier, land cover and sea level data for hydrological modeling of the Arctic ocean drainage basin

Large scale modelling using a catchment approach HYdrological Predictions for the Environment (HYPE) (Lindström et al. (2010), Hydrology Research) 23 million km sub-basins average spatial resolution =715 km 2 The Arctic-HYPE model: HYPE source code, WIKI, manuals, etc: Model setup (short version): 1.Sub-basin delineation based on DEM (Hydro 1K), Lakes (GLWD), and River discharge stations (GRDC etc) 2.Each sub-basin is divided in sub-units representing combinations of soil type (HWSD) and land cover (GlobCover) 3.Calibration with various data (snow, evaporation, galcier mass balance, discharge)

Available open global databases used

Flow to Ocean - trends in annual mean Pan-Arctic Ob, Yenisei, Lena, Sernaja Dvina, Pechora, Kolyma Yukon, Mackenzie, Peel, Back Overall, similar trends to Shiklomaniv & Lammers (2009) – but overestimated flow in North America (and no trend / declining) Trends in water balance and storages

Modelled water balance for the Arctic basin Trends in water balance and storages Trends in evaporation and precipitation < 1mm/year Increase in Prec and Runoff in last decade Storage change – 6 mm/year corresponding to glacier mass balance

 Negative trend in Glacier storage = - 6 mm/year for the entire basin:  Corresponds to -164 km 3 /yr in glacier volume  Probably too high – Glacier model need more attention!  Small changes in other storages Trends in water balance and storages Annual change in water storage: Modelled water storages in the Arctic basin

Assessment of CCI glacier, Land cover Progress (preliminary results): 1)CCI Glacier (RGI v4.0) and CCI Land Cover (v1.3-4) used to evaluate Arctic-HYPE (v3) glacier area and volume: Glacier area: Arctic-HYPE (v3) based on GlobCover (v2.2) (“permanent snow and ice”) CCI Land Cover (v1.3-4) gives more realistic snow and ice distribution in the Arctic: >100% difference between CCI LC and GlobCover However, CCI Land Cover (v1.3-4) gives ~30% larger area than CCI Glacier (RGI v4.0).

RGI region RGI area in model (km2) RGI area (fraction of total area in RGI region) RGI area (fraction of model area) Based on CCI LC (fraction of RGI area) Based on GlobCover LC (fraction of RGI area) 01 Alaska Western Canada/US Arctic Canada North Arctic Canada South Iceland Svalbard Scandinavia Russian Arctic North Asia Total Evaluation Glacier Area [km2] per RGI regions: 95% of Region 1-10 (excl Greenland) is covered by Arctic HYPE CCI clearly better than GlobCover (still +30%) Permanent snow and ice largely overestimate glacier area in Arctic North America and Arctic Russia/North Asia Assessment of CCI glacier, Land cover

WP3.9 Assessment of glacier, land cover and sea level data for hydrological modeling of the Arctic ocean drainage basin Volume from subbasin area [km3] Volume from RGI areas[km3] Progress (preliminary results): 1)CCI Glacier (RGI v4.0) and CCI Land Cover (v1.3-4) used to evaluate Arctic-HYPE (v3) glacier area and volume: Glacier volume based on non-linear area-volume relationship (Bahr et al, 1997, Grindsted, 2003): CCI Glacier outlines (RGIv4) was used to evaluate error when aggregating (or splitting) area from multiple glaciers in/between model sub-basins: Volume overestimated by 28% In combination with the area overestimation, current Arctic HYPE model overestimate Glacier volume with more than 200% compared to data derived from CCI Glacier!!

RGI region Volume from individual RGI areas (km3) Volume from total area [km3] Vol [total] / Vol [ind] Vol [CCI area] / Vol [RGI] Vol [GlobCover]/Vol [RGI] 01 Alaska Western Canada/US Arctic Canada North Arctic Canada South Iceland Svalbard Scandinavia Russian Arctic North Asia Total Evaluation Glacier Volume estimates per RGI regions: Volume estimated from total area overestimate volume from individual area by 28% Variation depending on: agreement glacier outlines and subbasins number of glaciers / subbasin Combination of area and volume estimation errors add up largely in current model! Assessment of CCI glacier, Land cover Eyafjallajökul, Iceland

WP3.9 Assessment of glacier, land cover and sea level data for hydrological modeling of the Arctic ocean drainage basin Progress (preliminary results): 2)CCI Land cover used to evaluate and improve Arctic-HYPE surface water area: Example from the area around the lower Ob: Globcover shows sparse vegetation CCI 2005 shows water bodies; Shrub or herbaceous cover; flooded; fresh/saline/brakish water. On average 6-10% increase, depending on method for combining information from CCI and GLWD. 3) CCI land cover time series 2000, 2005, 2010 show negative trend in Siberian deciduous needle- leaf vegetation: Due to increase in soil moisture as response to increased precipitation? To be evaluated 4) CCI Sea level - No results yet

Conclusions Preliminary conclusions CCI Glacier very useful for hydrological modelling: setup and evaluation of glacier area and volume Very high resolution and level of detail Global coverage Current limitations: Time series missing in RGI dataset needed for initialization, calibration, evaluation of long term modelling Users may compile information from other data sets: GLIMS/WGMS/literture/etc. CCI Land cover: Improved snow and ice area Increased water surface area Interesting trends in Arctic forest vegetation Current limitations: Static Surface water and Glacier information

Thank you Q & A