Snow samples were collected from several locations on the main MOSAiC ice floe on weekly basis. Snow samples for measurement of stable water isotopes (δ18O, δD,) were collected in three different layers (top, middle, bottom) using a metal density cutter. At first, samples were stored in sealed plastic bags and the air was squeezed out before closing the bags. At later stages of the expedition, samples were stored in plastic cups with lids. Later the samples were thawed completely at room temperature and poured into 20 ml glass vials and sealed with parafilm tape and stored at 4°C. Oxygen and hydrogen isotope analyses were carried out at the ISOLAB Facility at AWI Potsdam (https://hdl.handle.net/10013/sensor.ddc92f54-4c63-492d-81c7-696260694001) with mass spectrometers (DELTA-S Finnigan MAT, USA): https://hdl.handle.net/10013/sensor.af148dea-fe65-4c87-9744-50dc4c81f7c9 https://hdl.handle.net/10013/sensor.62e86761-9fae-4f12-9c10-9b245028ea4c. employing the equilibration method (details in Meyer et al., 2000). δ18O and δD values were given in per mil (‰) vs. Vienna standard mean ocean water (V-SMOW) as the standard. The second order parameter d excess was computed according to: d excess = δD-8 δ18O (Dansgaard, 1964).