Initial results from Arctic cores recovered by the IODP Expedition 302 (ACEX) from the Arctic indicate that during the early Eocene time of extreme global warmth the Arctic was ice-free and supported a highly productive ecosystem in very brackish near surface waters. Under this award, the PIs propose to constrain the likely interactions between the Arctic and the global ocean during these extremely warm times and to trace these interactions through the global cooling that followed by developing a history Sr and Nd isotopes in Arctic Ocean waters. This study will involve graduate students and addresses the question of global climate change.