In his paleoceanographic studies, Udara Amarathunga combines high-resolution multiproxy records with both physical oceanographic and climate modeling. With the 2023 Harry Elderfield Student Paper Award, Amarathunga is recognized for his lead-authored Nature Geoscience article titled “Sill-controlled salinity contrasts followed post-Messinian flooding of the Mediterranean,” which reexamines the final phases of the Messinian salinity crisis (MSC), one of the most dramatic oceanographic events of the Cenozoic era. The MSC resulted from tectonic restriction of the Atlantic-Mediterranean gateway approximately 6 million years ago, leading to a decline in sea level within the Mediterranean Basin and massive evaporite deposition.

Eventually, the MSC was terminated at the Miocene-Pliocene (M-P) boundary 5.3 million years ago, reestablishing normal marine conditions as the Atlantic waters refilled the Mediterranean. Amarathunga’s data and simulations offer clarity as to how the MSC was terminated.

Amarathunga began by clarifying the characteristics of the “mystery sapropel,” an organic-rich layer that occurs at the M-P boundary. Amarathunga’s analyses and exhaustive review of existing data showed that the mystery sapropel occurred in the eastern basin of the Mediterranean but not the western basin. Moreover, while Mediterranean sapropels occur periodically throughout the Mediterranean Sea sediment record, they are usually formed during a Northern Hemisphere summer insolation maximum. In contrast, Amarathunga showed that the mystery sapropel was deposited across two consecutive insolation maxima, a period 4–6 times longer than observed for subsequent sapropels, indicating that its mechanism of formation was unique. Next, working with physical oceanographic colleagues, Amarathunga developed a numerical model of the important physical processes involved in reconnecting the Mediterranean to the Atlantic. Amarathunga’s model simulations, in the context of his findings regarding the mystery sapropel, reveal that the Mediterranean Sea was in a significantly drawn- down state when the reconnection occurred. This resulted in a massive cascade into the western Mediterranean, which mixed the western basin. In contrast, the more gradual inflow into the eastern basin left it salinity stratified for thousands of years, generating the mystery sapropel. The article was highlighted in a Nature Geoscience News & Views article by Angelo Camerlenghi, who wrote that “this study demonstrates […] the extraordinary value of the scientific ocean drilling legacy data as a long-lasting source of primary information for application of the evolving analytical and numerical modelling techniques.” Amarathunga, a native of Sri Lanka, has completed his Ph.D. at Australian National University and has been awarded the Harry Hess Postdoctoral Fellowship at Princeton University.

—Daniel M. Sigman, Department of Geosciences, Princeton University, Princeton, N.J.

I am immensely grateful to receive the Harry Elderfield Student Paper Award for the year 2023 at the AGU Fall Meeting. I thank Prof. Daniel Sigman for his heartening citation comments on this recognition. I am much obliged to the AGU Paleoceanography and Paleoclimatology award committee for selecting my work for this award, which certainly is a massive encouragement for my future research work. It is fascinating to realize how Harry Elderfield’s 4-decade-old work on ocean chemistry paved the way for the future generations of scientists to develop an understanding of past ocean conditions, to the present level. I was fortunate to have had the chance to join Prof. Eelco Rohling’s research group at Australian National University for my Ph.D., during which I was able to utilize chemical signatures of marine sediments to uncover some “salty secrets” of the Mediterranean Basin. I am indebted to Prof. Andy Hogg for his continuous guidance in perceiving physical oceanographic concepts, which allowed me to quantitatively explore Mediterranean Sea evolution. It is irrefutable that under the emerging climate crisis, the Earth system is in a state of emergency. Discerning the past responses of oceans and climate to changing boundary conditions considerably increases our ability to better prepare for the future. Hence, it is my hope to follow in Harry Elderfield’s footsteps as an innovative scientist, to further improve our understanding of paleoceanographic proxies and their applications. —Udara Amarathunga, Princeton University, Princeton, N.J.