The focus of this study by researchers at the Lamont-Doherty Earth Observatory of Columbia University is to test how the Subarctic North Pacific responds to and potentially mitigates climate change. The Subarctic Pacific constitutes one of the high-nutrient-low chlorophyll regions where the biological pump is relatively inefficient at transferring carbon from the atmosphere to the deep sea. Iron, contained in mineral dust from Chinese deserts, is thought to stimulate biological production in this region. However, our understanding of the links between dust, biological production and climate is hampered by the lack of reliable dust flux records in the Subarctic North Pacific as well as longstanding discrepancies among specific techniques that have been used in previous research to reconstruct biological productivity.
Cores collected during a recent German-led expedition (INOPEX) provide extensive coverage of this previously largely undersampled remote region and offer a unique opportunity for study. Using a suite of geochemical proxies (thorium and uranium isotopes, helium isotopes, and trace elements), the researchers will produce a map of the spatial pattern of dust supply and biological productivity and calibrate it by comparing to present day information from satellites and other observations. The researchers will then apply their calibration to down-core records, focusing on the abrupt climate changes of the last deglaciation. The sequence from the cold and dusty Heinrich Stadial 1, through the dust-poor Bølling-Allerød warm period and a return to the near-glacial conditions of the Younger Dryas stadial provides for an outstanding natural experiment to test how the Subarctic North Pacific?s ecosystem responds to and mediates climate change.
Broader impacts include involvement of undergraduates and high school students in the research, training of local high school teachers, and enhancing international collaborations. In addition, the results of this international collaboration will inform decision makers in exploring large-scale artificial iron fertilization of the ocean as a geo-engineering option to mitigate global warming. Reliable estimates of the long-term carbon sequestration capacity and impact on the ecosystem remain controversial. This work will assess the past response to natural variability of iron input in one of the key regions of the global ocean and will, in turn, lay the foundation to develop quantitative predictions about the possible efficacy and consequences of artificial iron fertilization.
