Glacial melting pulses in the Antarctica: Evidence for different responses to regional effects of global warming recorded in Antarctic bivalve shell (Laternula elliptica)

摘要

Meltwater history of the Antarctic bivalve Laternula elliptica in Maxwell Bay, King George Island near the Antarctic Peninsula was reconstructed during the shell growth. High resolution trace elemental and stable isotopic compositions along the aragonite outer part of the shell together with growth bands shows that the shell lived for 9 years with distinct annual cycles. Also oxygen and carbon isotope values reveal the local meltwater history in Antarctic Peninsula region. More negative oxygen isotope values than the predicted equilibrium values clearly show that oxygen isotope depletion is due to lower salinity of seawater by glacial melting. This is also confirmed by the similar trend of low carbon isotope values as well as monitored sea surface salinity values. Comparing delta O-18 values of previous results using the same bivalve species, more negative values from the Antarctic Peninsula (Maxwell Bay) during the austral winter than from East Antarctica (Syowa Coast and Ross Sea) suggests that perennial glacial melting influenced seawater delta O-18 composition near the peninsula. Also, more negative and variable bivalve delta O-18 values during austral summer indicate that meltwater pulses fluctuated greatly in the study area. Distinctively different trends in bivalve delta O-18 profiles between the Antarctic Peninsula and East Antarctica may reflect differential responses to regional warming with regard to the recent global warming over the past few decades.