It was almost Christmas time in Antarctica, few days before the summer solstice, once we landed over the Hells Gate Ice Shelf with the helicopter, coming from the Zucchelli Station, when we noticed something strange. The ice shelf, which has been blue all across the previous month of observations, was now completely white. But the strange thing was that no snowfall recently happened, but the opposite of it. Sunny and warm (close to 0°C) days, with almost no wind and clouds. But that's not strange enough, walking on that white surface, we noticed the different compactness in respect to the blue ice, under our crampons. Now, the ice shelves turned to be a way crunchier than before. At that time, we couldn't imagine that we were walking on something never studied before over Antarctic Ice Shelves.

Immediately, the discouragement took over. We were supposed to be there to analyse the dark matter over the ice and instead we were facing the brightest ice ever seen in the area. It was also true that new supraglacial ponds were formed as well, but the predominancy of the white surface was evident. Nevertheless, after an initial moment of astonishment we realized the uniqueness of this event. After having studied a lot concerning the region, we couldn't remember anything like this phenomenon. It meant we were witness of something new. Therefore, we turned on our instrumentation and started to collect measurements and samples all across the ice shelf. Few days later, we even realised that all the area of Terra Nova Bay was interested by this phenomenon, including the much wider Nansen Ice Shelf.

During the following days, and also once come back to Italy a month later, we started to study possible reasons to this phenomenon and to listen to the opinion of other researchers. First, we discovered that this white ice has been already observed in the past in this area, but no official scientific records were still present. On the other hand, we found out that similar phenomena were observed in the Arctic over glaciers, sea ice and lake ice. Simply, the penetration of solar radiation beneath glacier surfaces has the potential to induce melting leading to the formation of a porous white layer commonly known as weathering crust. Moreover, we discovered that this crust occurred after a period of increasing temperature, relative humidity, low wind speed and clear sky conditions. We then realised that this "weathering crust" was the thing we observed over the ice shelves of Terra Nova Bay, despite no previous testimonies were recorded in the area... or rather, in all Antarctic ice shelves! In fact, it has been only described before in Antarctica over glaciers of the Dry Valleys, 300 km south of Terra Nova Bay.

Therefore, with a good amount of data, from photos, satellite and drone images, to spectroscopy measurements, it was definitely time to start telling our story.

We succeeded in estimating the radiative impact of the weathering crust formation, demonstrating a predominant negative albedo (the measure of how much light a surface reflects) feedback over blue ice areas (on 93% of the study area), with respect to positive melt-albedo feedback. In fact, the majority of the analysed ice shelves were affected by the brightening of the surface, which turned white (very high albedo) from a blueish colour. Only a smaller portion of the ice shelves were characterised by darkening of the surface, mostly due to supraglacial-pond formations for melting effect. Furthermore, thanks to our field observations together with measurements collected by an automatic weather station close to the area, we could also demonstrate that the crust developed as a consequence of increasing temperature, relative humidity, low wind speed and clear sky conditions.

In this perspective, we claim that this new process should be included in regional climate modelling of the Antarctic Ice Shelves, since our findings are of importance for future large-scale and regional SMB models for Antarctica, which do not consider this