Methodology:

Data was gathered during the 2016 Black and Bloom field campaign and processed in the LowTex and MicroLab laboratories at the University of Bristol. Details on sample collection, processing and analysis can be found in the referenced publication, and all R data analysis scripts are available here.

In-situ data collection spanned June-August 2016. Model runs spanned 1st June 2016 - 1st September 2016. All in-situ observations and incubation studies were conducted in proximity to the IMAU (Utrecht) automatic weather station S6 of the K-Transect in southwest Greenland (67.04 N, 49.07W). Model runs were performed for sites S6, S8, S9 and S10 of the K-Transect.

Data collection:

Instrumentation:

Algal cell abundance was quantified using a Fuchs-Rosenthal haemocytometer (Lancing, UK) on a LeicaDM 2000 epifluorescence microscope with attached MC120 HD camera (Leica, Germany). Photophysiology was assessed using a Water-PAM fluorometer with attached cuvette system (Walz GmBH, Germany).

Algal pigmentation was assessed using a combination of High-Performance

Liquid Chromatography (HPLC) using an Agilent 1100 HPLC equipped with a diode-array detector, and spectrophotometric wave-scans using a WPA Light-Wave II UV/Visible spectrophotometer (Biochrom, UK). Albedo modelling was achieved using the radiative transfer model BioSNICAR-GO. GrIS surface ice broadband albedo for June, July and August 2016 were derived from clear-sky MODIS MOD10A1 satellite observations at 500 m horizontal resolution. Glacier algal biomass was modelled in GrIS surface ice forced by hourly snowpack thickness, shortwave-down radiation and air temperature from re-analysis outputs produced by the regional climate model MARv3.8.1 forced with ERA

-Interim at 20km resolution.

Data quality:

All analyses performed on data are available as associated script files.