ALBERT

Description: We assessed sediment coring, data acquisition, and publications from the North Pacific (north of 30°N) from 1951-2016. There are 2134 sediment cores collected by American, French, Japanese, Russian, and international research vessels across the North Pacific (including the Pacific Subarctic Gyre, Alaskan Gyre, Japan Margin, and California Margin, 1391 cores), Sea of Okhotsk (271 cores), Bering Sea (123 cores), and Sea of Japan (349 cores) reported here. All existing metadata associated with these sediment cores are documented, including coring date, location, core number, cruise number, water depth, vessel metadata, and coring technology. North Pacific age models are based on isotope stratigraphy, radiocarbon dating, magnetostratigraphy, biostratigraphy, tephrochronology, % opal, color, and lithophysical proxies. Here, we evaluate the iterative generation of each published age model and provide documentation of each dating technique used, as well as sedimentation rates and age ranges. We categorized cores according to availability of a variety of proxy evidence, including biological (e.g. benthic and planktonic foraminifera assemblages), geochemical (e.g. heavy metal concentrations), isotopic (e.g. bulk sediment nitrogen and carbon isotopes), and stratigraphic (e.g. preserved laminations) proxies. This database is a unique resource to the paleoceanographic and paleoclimate communities, and provides cohesive accessibility to sedimentary sequences, age model development, and proxies.

Description: A climatically induced acceleration in ocean‐driven melting of Antarctic ice shelves would have consequences for both the discharge of continental ice into the ocean and thus global sea level, and for the formation of Antarctic Bottom Water and the oceanic meridional overturning circulation. Using a novel gas‐tight in situ water sampler, noble gas samples have been collected from six locations beneath the Filchner Ice Shelf, the first such samples from beneath an Antarctic ice shelf. Helium and neon are uniquely suited as tracers of glacial meltwater in the ocean. Basal meltwater fractions range from 3.6% near the ice shelf base to 0.5% near the sea floor, with distinct regional differences. We estimate an average basal melt rate for the Filchner‐Ronne Ice Shelf of 177 ± 95 Gt/year, independently confirming previous results. We calculate that up to 2.7% of the meltwater has been refrozen, and we identify a local source of crustal helium.

Description: Mg/Ca ratio paleothermometry in foraminifera is an important tool for the reconstruction and interpretation of past environments. However, existing Mg/Ca:temperature relationships for planktic species inhabiting mid- and high- latitude environments are limited by a lack of information about the development and impact of low-Mg/Ca ratio “crusts” and the influence of the carbonate system on Mg/Ca ratios in these groups. To address this, we cultured individual specimens of Neogloboquadrina incompta and Neogloboquadrina pachyderma in seawater across a range of temperature (6 °- 12 °C) and pH (7.4 – 8.2). We found by laser ablation inductively couple mass spectrometry analyses of shells that culture-grown crust calcite in N. incompta had a lower Mg/Ca ratio than ontogenetic calcite formed at the same temperature, suggesting that temperature is not responsible for the low Mg/Ca ratio of neogloboquadrinid crusts. The Mg/Ca:temperature relationship for ontogenetic calcite in N. incompta was consistent with the previously published culture-based relationship and no significant relationship was found between Mg/Ca ratios and pH in this species. However, the Mg/Ca ratio in laboratory cultured N. pachyderma was much higher than that reported in previous core-top and sediment trap samples, due to lack of crust formation in culture. Application of our ontogenetic calcite-specific Mg/Ca:temperature relationships to fossil N. pachyderma and N. incompta from five intervals in cores from the Santa Barbara Basin and the Bering Sea show that excluding crust calcite in fossil specimens may improve Mg/Ca-based temperature estimates.

Description: Coral reefs are built of calcium carbonate (CaCO3) produced biogenically by a diversity of calcifying plants, animals and microbes. As the ocean warms and acidifies, there is mounting concern that declining calcification rates could shift coral reef CaCO3 budgets from net accretion to net dissolution. We quantified net ecosystem calcification (NEC) and production (NEP) on Dongsha Atoll, northern South China Sea, over a two-week period that included a transient bleaching event. Peak daytime pH on the wide, shallow reef flat during the non-bleaching period was 8.5, significantly elevated above that of the surrounding open ocean (8.0-8.1) as a consequence of daytime NEP (up to 112 mmol C/m**2/h). Diurnal-averaged NEC was 390?+/-?90 mmol CaCO3/m**2/day, higher than any other coral reef studied to date despite comparable calcifier cover (25%) and relatively high fleshy algal cover (19%). Coral bleaching linked to elevated temperatures significantly reduced daytime NEP by 29 mmol C/m**2/h. pH on the reef flat declined by 0.2 units, causing a 40% reduction in NEC in the absence of pH changes in the surrounding open ocean. Our findings highlight the interactive relationship between carbonate chemistry of coral reef ecosystems and ecosystem production and calcification rates, which are in turn impacted by ocean warming. As open-ocean waters bathing coral reefs warm and acidify over the 21st century, the health and composition of reef benthic communities will play a major role in determining on-reef conditions that will in turn dictate the ecosystem response to climate change.