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We aim to determine abundances of Li, O and Na in a sample of of 110 turn-off(TO) stars, in order to study the evolution of light elements in this clusterand to put our results in perspective with observations of other globular andopen clusters, as well as with field stars. We use medium resolution spectraobtained with the GIRAFFE spectrograph at the ESO 8.2m Kueyen VLT telescope anduse state of the art 1D model atmospheres and NLTE line transfer to determinethe abundances. We also employ CO5BOLD hydrodynamical simulations to assess theimpact of stellar granulation on the line formation and inferred abundances.Our results confirm the existence of Na-O abundance anti-correlation and hinttowards a possible Li-O anti-correlation in the TO stars of 47 Tuc. We find noconvincing evidence supporting the existence of Li-Na correlation. The obtained3D NLTE mean lithium abundance in a sample of 94 TO stars where Li lines weredetected reliably, $\langle A({\rm Li})_{\rm 3D~NLTE}\rangle = 1.78 \pm 0.18$dex, appears to be significantly lower than what is observed in other globularclusters. At the same time, star-to-star spread in Li abundance is also largerthan seen in other clusters. The highest Li abundance observed in 47 Tuc isabout 0.1 dex lower than the lowest Li abundance observed among the un-depletedstars of the metal-poor open cluster NGC 2243. The lithium abundances in 47Tuc, when put into context with observations in other clusters and field stars,suggest that stars that are more metal-rich than [FeH] \sim -1.0 experiencesignificant lithium depletion during their lifetime on the main sequence, whilethe more metal-poor stars do not. Rather strikingly, our results suggest thatinitial lithium abundance with which the star was created may only depend onits age (the younger the star, the higher its Li content) and not on itsmetallicity.

Abundances of lithium, oxygen, and sodium in the turn-off stars of Galactic globular cluster 47 Tuc