GNOM v1.0: an optimized steady-state model of the modern marine neodymium cycle

Spatially distant sources of neodymium (Nd) to the ocean that carry different isotopic signatures (εNd) have been shown to trace out major water masses and have thus been extensively used to study large-scale features of the ocean circulation both past and current. While the global marine Nd cycle is qualitatively well understood, a complete quantitative determination of all its components and mechanisms, such as the magnitude of its sources and the paradoxical conservative behavior of εNd, remains elusive. To make sense of the increasing collection of observational Nd and εNd data, in this model description paper we present and describe the Global Neodymium Ocean Model (GNOM) v1.0, the first inverse model of the global marine biogeochemical cycle of Nd. The GNOM is embedded in a data-constrained steady-state circulation that affords spectacular computational efficiency, which we leverage to perform systematic objective optimization, allowing us to make preliminary estimates of biogeochemical parameters. Owing to its matrix representation, the GNOM model is additionally amenable to novel diagnostics that allow us to investigate open questions about the Nd cycle with unprecedented accuracy. This model is open-source and freely accessible, is written in Julia, and its code is easily understandable and modifiable for further community developments, refinements, and experiments.</p

GNOM: An optimized steady-state model of the modern global marine neodymium cycle

&lt;p&gt;Fixes starting scavenging constants&lt;/p&gt

Trace metal and black carbon data in aerosol, seawater, and floodwater samples taken in southern California during the 2017 Thomas Fire

Aerosol, seawater, and floodwater samples were taken during the 2017 California Thomas Fire and subsequent flash flood event. These samples were used to examine how fire-flood sequences affect metal and black carbon delivery to coastal waters, such as the Santa Barbara Basin (SBB). On day 11 of the Thomas Fire, aerosols sampled at sea level under a smoke plume over the SBB found high levels of PM2.5, levoglucosan, and black carbon (average: 49 μg/m^3, 1.05 μg/m^3, 14.93 μg/m^3, respectively) and both soluble and total aerosol metal concentrations were consistent with a forest fire signature. Metal, nutrient, and chlorophyll a concentrations in surface seawater (average: 2.42 nM Fe, 0.14 µM phosphate, and 0.44 µgChla/L) were similar to concentrations during non-fire conditions, thus we could not establish fire-related increases in the SBB surface waters. On days 37 to 40 of the fire, before, during, and after a flash flood in the Ventura River, dissolved organic carbon, dissolved black carbon, and dissolved metal concentrations were positively correlated with discharge. Our findings confirm that black carbon and metals were released by the Thomas Fire and transported by both atmospheric and fluvial pathways