ALBERT

Description: We present the first continuous alkenone-based estimate of northern hemisphere sea surface temperatures from ~8.5-22 Myr. Reconstructed temperatures range from 11 to 20°C higher than modern mean annual temperature, with a clear maximum during the mid-Miocene Climatic Optimum (MCO). These results establish that the MCO warming and partial deglaciation of the Antarctic was part of a global climatic warming.

Description: Data include area fractions of sea ice surface types (white ice/snow, bright melt ponds, dark melt ponds, open water, bare ice) obtained from aerial imagery during 29 research flights that were performed within the scope of the Multidisciplinary Drifting Observatory for the Study of Arctic Climate (MOSAiC) experiment from May 2020 until end of September 2020. The images were taken every four seconds by fisheye lens cameras (Canon EOS digital) installed on a helicopter or HELiPOD, a towed survey probe. The data set provides additional information about the attitude and geographic location of the helicopter/HELiPOD. Only images that passed the quality checks were included.

Description: Measurements of transmitted irradiance under sea ice and corresponding incident solar radiation at the surface have been performed during the Polarstern expedition PS131, ATWAICE. During this expedition, three major ice floes were revisited to repeat measurements with a time gap of approximately one week and thereby analyze temporal development. Additionally, measurements on another ice floe were repeated 8 times within one day to observe the daily cycle of incoming and transmitted irradiance. All observations took place in the Fram Strait, north of Svalbard, between July 13 and August 6, 2022. The radiation measurements have been performed with Ramses spectral radiometers (TriOS, Rastede, Germany) in the wavelength range 316 to 952 nm. The incoming irradiance sensor was installed at approximately 1 m above the sea ice surface. The transmittance sensor was lowered through a hole (diameter about 10 cm) into the water down to 40 to 50 m depth. There are three datasets, two of them contain the raw data of the incoming and transmittance sensors. The third file contains temporally interpolated data (to 1s) of integrated intensity of both sensors and an estimation of the transmittance which is the ratio of the incoming and the transmitted irradiance. All times are given in UTC. The "incoming" dataset contains the date and time as index, the integration time of the sensor in ms and the measured intensity per channel in mW/m²/nm. The "transmitted" dataset contains the same information for the sensor in the water complemented with the sensor depth in meters and its inclination in two directions in degree (°). The "interpolated" dataset contains again the date and time, sensor depth and inclination information, and the integration times of the two sensors complemented with the integrated intensity measured by the two sensors in W/m² and their ratio which is the transmittance in percent (%). Additionally included, are plots of the sensor depth-transmittance relation for all 19 observations and the ice thickness and ice draft measured at the measurement site. Two figures show the measurement setup.