ALBERT

Description: The history of the Arctic Ocean during the Cenozoic era (0–65 million years ago) is largely unknown from direct evidence. Here we present a Cenozoic palaeoceanographic record constructed from 〉400 m of sediment core from a recent drilling expedition to the Lomonosov ridge in the Arctic Ocean. Our record shows a palaeoenvironmental transition from a warm 'greenhouse' world, during the late Palaeocene and early Eocene epochs, to a colder 'icehouse' world influenced by sea ice and icebergs from the middle Eocene epoch to the present. For the most recent approx14 Myr, we find sedimentation rates of 1–2 cm per thousand years, in stark contrast to the substantially lower rates proposed in earlier studies; this record of the Neogene reveals cooling of the Arctic that was synchronous with the expansion of Greenland ice (approx3.2 Myr ago) and East Antarctic ice (approx14 Myr ago). We find evidence for the first occurrence of ice-rafted debris in the middle Eocene epoch (approx45 Myr ago), some 35 Myr earlier than previously thought; fresh surface waters were present at approx49 Myr ago, before the onset of ice-rafted debris. Also, the temperatures of surface waters during the Palaeocene/Eocene thermal maximum (approx55 Myr ago) appear to have been substantially warmer than previously estimated. The revised timing of the earliest Arctic cooling events coincides with those from Antarctica, supporting arguments for bipolar symmetry in climate change.

Description: Over much of the ocean’s surface, productivity and growth are limited by a scarcity of bioavailable nitrogen. Sedimentary δ15N records spanning the last deglaciation suggest marked shifts in the nitrogen cycle during this time, but the quantification of these changes has been hindered by the complexity of nitrogen isotope cycling. Here we present a database of δ15N in sediments throughout the world’s oceans, including 2,329 modern seafloor samples, and 76 timeseries spanning the past 30,000 years. We show that the δ15N values of modern seafloor sediments are consistent with values predicted by our knowledge of nitrogen cycling in the water column. Despite many local deglacial changes, the globally averaged δ15N values of sinking organic matter were similar during the Last Glacial Maximum and Early Holocene. Considering the global isotopic mass balance, we explain these observations with the following deglacial history of nitrogen inventory processes. During the Last Glacial Maximum, the nitrogen cycle was near steady state. During the deglaciation, denitrification in the pelagic water column accelerated. The flooding of continental shelves subsequently increased denitrification at the seafloor, and denitrification reached near steady-state conditions again in the Early Holocene. We use a recent parameterization of seafloor denitrification to estimate a 30–120% increase in benthic denitrification between 15,000 and 8,000 years ago. Based on the similarity of globally averaged δ15N values during the Last Glacial Maximum and Early Holocene, we infer that pelagic denitrification must have increased by a similar amount between the two steady states.

Description: Nitrous oxide is a potent greenhouse gas and a key compound in stratospheric ozone depletion. In the ocean, nitrous oxide is produced at intermediate depths through nitrification and denitrification, in particular at low oxygen concentrations. Although a third of natural emissions of nitrous oxide to the atmosphere originate from the ocean, considerable uncertainties in the distribution and magnitude of the emissions still exist. Here we present high-resolution surface measurements and vertical profiles of nitrous oxide that include the highest reported nitrous oxide concentrations in marine surface waters, suggesting that there is a hotspot of nitrous oxide emissions in high-productivity upwelling ecosystems along the Peruvian coast. We estimate that off Peru, the extremely high nitrous oxide supersaturations we observed drive a massive efflux of 0.2–0.9 Tg of nitrogen emitted as nitrous oxide per year, equivalent to 5–22% of previous estimates of global marine nitrous oxide emissions. Nutrient and gene abundance data suggest that coupled nitrification–denitrification in the upper oxygen minimum zone and transport of resulting nitrous oxide to the surface by upwelling lead to the high nitrous oxide concentrations. Our estimate of nitrous oxide emissions from the Peruvian coast surpasses values from similar, highly productive areas.

Description: Este informe – Estudio sobre medidas para apoyar esfuerzos de conservación en áreas fuera de la jurisdicción nacional en la región del Pacífico Sudeste – pretende proporcionar recomendaciones para la conservación y uso sostenible de la biodiversidad marina en áreas fuera de la jurisdicción nacional (ABNJ, por sus siglas en inglés) en la región del Pacífico Sudeste. Estas recomendaciones incluyen consideraciones para establecer nuevas medidas de conservación y manejo y expandir o mejorar en la región otras medidas existentes; así como el uso de herramientas que apoyan el desarrollo de medidas de conservación. Este informe ha sido elaborado por investigadores del proyecto STRONG High Seas a partir de una revisión bibliográfica de artículos académicos, análisis de datos, conocimientos de las partes interesadas y experiencias recogidas en talleres de expertos celebrados en la región de interés del proyecto en 2021. La información presentada aquí pretende apoyar a tomadores de decisiones, incluyendo funcionarios de los gobiernos, el sector privado y otras partes interesadas que trabajen en el tema de la gobernanza oceánica en ABNJ y que participen o tengan interés en el actual desarrollo de la Conferencia Intergubernamental sobre un instrumento internacional jurídicamente vinculante en el marco de la Convención de las Naciones Unidas sobre el Derecho del Mar (CONVEMAR) relativo a la conservación y el uso sostenible de la diversidad biológica marina de las áreas fuera de la jurisdicción nacional (BBNJ, por sus siglas en inglés). Este informe hace parte de una serie de informes publicados por el proyecto STRONG High Seas [Strengthening Regional Ocean Governance for the High Seas (June 2017 – May 2022)], que cubren aspectos de la gobernanza de los océanos con un foco geográfico en la región del Pacífico Sudeste (y el Atlántico Sudeste).

Description: This report - Study on Measures to Support Conservation Efforts in Areas Beyond National Jurisdiction in the Southeast Pacific Region - aims to provide recommendations for the conservation and sustainable use of marine biodiversity in areas beyond national jurisdiction (ABNJ) in the Southeast Pacific region. These recommendations include considerations for establishing new conservation and management measures and expanding or improving existing measures in the region, as well as the use of tools to support the development of conservation measures. This report has been prepared by STRONG High Seas project researchers based on a literature review of cademic articles, data analysis, stakeholder insights, and experiences gathered at expert workshops held in the project’s focus regions in 2021. The information presented here is intended to support decision-makers, including government officials, the private sector and other stakeholders working on ocean governance in ABNJ who are involved or have an interest in the ongoing development of the Intergovernmental Conference on an international legally binding instrument under the United Nations Convention on the Law of the Sea (UNCLOS) on the conservation and sustainable use of marine biological diversity in areas beyond national jurisdiction (BBNJ). This report is part of a series of reports published by the STRONG High Seas project [Strengthening Regional Ocean Governance for the High Seas (June 2017 - May 2022)], covering aspects of ocean governance with a geographic focus on the Southeast Pacific (and Southeast Atlantic) region.