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Andrew R. Margolin
Research

Present Projects
Hansell Lab:
Environmental Impacts on Carbon Biogeochemistry in Marginal Seas
Committee Members: Profs. Dennis A. Hansell (chair), William E. Johns, Frank J. Millero & Peter K. Swart



Research Chapter I:
Net Removal of Dissolved Organic Carbon in the Anoxic Waters of the Black Sea

The Black Sea is the world's largest anoxic basin, having dissolved organic carbon (DOC) concentration ~2.5 times higher than the open ocean (Ducklow et al., 2007). Anoxia may inhibit the mineralization of DOC, causing it to accumulate (Sexton et al., 2011), however, net removal is detected in the anoxic, suboxic and sub-euphotic layers of the Black Sea (Margolin et al., 2016). Rivers, such as the Danube River, contribute concentrations of 300 μM DOC to the Black Sea (Cauwet et al., 2002), and this river input is likely responsible for the Black Sea's relatively high DOC concentrations (Margolin et al., 2016).

Research Chapter II:
Tracing Organic Matter Dynamics in the Black Sea: Insights from Optical Analyses

The Black Sea's DOC concentrations (~120-200 μM) are higher than in the open ocean and Mediterranean Sea; previous studies suggested that input of terrigenous DOC from rivers is responsible for the relatively high concentrations (Ducklow et al., 2007; Margolin et al., 2016). To obtain information on the basin's DOC composition (e.g., humic- or protein-like) and predominant origin (i.e., terrigenous or marine), the optical properties (absorption and fluorescence) of chromophoric dissolved organic matter (CDOM) were measured in 111 samples collected across the Black Sea salinity, redox and DOC gradients. In the basin's oxic layer (upper ~100 m), CDOM correlates with DOC, suggesting that they are controlled by same processes. In the underlying anoxic layer (lower ~2000 m), DOC increases by ~10% with depth while CDOM ~doubles, correlating well with H2S and nutrients. These findings indicate that a fraction of in situ DOC is transformed by microbes in the anoxic water, altering its CDOM composition, and/or that composition changes as a result of external inputs (e.g., sinking particles) with little net concentration change.

Research Chapter III:
Biogeochemical Distributions and Carbon Exchanges Between the Deep Intra-Americas Seas

The Gulf of Mexico (GoM) and basins of the Caribbean (i.e., Yucatan, Cayman, Colombia and Venezuela Basins) are collectively referred to as the Intra-Americas Seas (IAS). These five basins are separated from each other by passages with sill depths (at ~2000 m depth) that restrict deep exchanges between the basins and with the North Atlantic (Sturges, 2005). The distribution of dissolved inorganic carbon is explored in the deep IAS basins with respect to sill depths.


The Carbon System in the Canadian Basin, Arctic Ocean

In August-October 2015, I participated in the U.S. GEOTRACES / U.S. Repeat Hydrography Arctic Expedition to sample and analyze the carbon system in seawater aboard the USCGC Healy. I worked with the Marine Physical Chemistry Group to analyze seawater for pH, total alkalinity (AT) and DIC, also collecting DOC samples for the Hansell Lab. Analysis of DOC samples and data interpretation have recently begun. This data will expand upon my dissertation topic, however, will not be included in it since I will be finishing this summer.

To learn more about my experience during the cruise, you can visit my cruise blog, Arctic Andy and the 2015 U.S. GEOTRACES Arctic Expedition, my Twitter feed, @armargolin, or my Instagram photos, #HLY1502.


Past Projects
Woods Hole Oceanographic Institution Guest Studentship:
Cold-Water Coral Paleo-Biogeography in the Drake Passage

During the summer of 2011, I spent 33 days aboard the RVIB Nathaniel B. Palmer in the Drake Passage collecting cold-water corals for use as paleoceanographic climate proxies. To learn more about our cruise, which was featured in The Antarctic Sun, visit our "Antarctic Corals" cruise blog. Following the cruise, I spent the rest of my summer at Woods Hole Oceanographic Institution (WHOI), as a Guest Student, to radiocarbon date over 400 coral subsamples at the National Ocean Sciences Accelerator Mass Spectrometry (NOSAMS) Facility. The follow summer, I spent three weeks back at WHOI before beginning graduate school, where I focused on writing about the results from this project. Since my last summer at WHOI, the paper has been published in the journal of Deep-Sea Research Part II: Topical Studies in Oceanography, entitled Temporal and spatial distributions of cold-water corals in the Drake Passage: Insights from the last 35,000 years. Shortly after the paper was published, I received the Continuous Flow Accelerator Mass Spectrometry (CFAMS) Prize from NOSAMS for my work on the paper, which was recognized as "a significant contribution to the scientific field." I was advised by Prof. Laura Robinson (University of Bristol/WHOI) for this project.


Ocean Biogeochemistry Research Group:
Changes and Trends in pH Throughout the Southern Ocean

In January of 2011, I joined the Ocean Biogeochemistry Research Group at CU's Institute of Arctic and Alpine Research (INSTAAR), where I studied pH change throughout the Southern Ocean. I utilized the Repeat Hydrography dataset to assess pH change, and used the CO2SYS program in MATLAB to calculate pH where it was not measured. I wrote my senior honors thesis on this work, entitled Measured and Estimated pH Change and Trends Throughout the Southern Ocean, 1972-2011. I was advised by Profs. Nicole Lovenduski (ATOC, committee chair), Jose-Luis Jimenez (Chemistry/ATOC), and Cortlandt Pierpont (Chemistry) for my honors thesis.

In addition to the work on my thesis project, I worked with Profs. Galen McKinley (University of Wisconsin − Madison) and my advisor, Nicole Lovenduski, to investigate changes in the North Atlantic carbon sink. I spent the first part of the summer in 2012 working on this project, exploring satellite chlorophyll a at the ocean surface and nutrient distributions in the top 1 km of the water column. Results from my work on this project contributed to presentations at NASA Applied Sciences' third biannual Air Quality Applied Sciences Team (AQAST) Meeting and the Integrated Marine Biogeochemistry and Ecosystem Research (IMBER)'s ClimECO3 Summer School in 2012.


Fox-Kemper Research Group:
Eddy Kinetic Energy and Diffusivity

My oceanographic research career began in February of 2009, when I joined the Fox-Kemper Research Group at CU's Cooperative Institute for Research in Environmental Sciences (CIRES) (now at Brown University) as an undergraduate research assistant. I studied eddy kinetic energy and eddy diffusivity using MATLAB to analyze data and contribute to other research within the group. Results from my work on the relationship between eddy diffusivity and eddy kinetic energy contributed to multiple presentations in 2010, including the American Geophysical Union's 2010 Ocean Sciences Meeting. I was advised by Prof. Baylor Fox-Kemper for this project, who introduced me to Prof. Nicole Lovenduski and continued to be involved with my research at CU in the Ocean Biogeochemistry Research Group.



This website was designed and is maintained by Andrew R. Margolin,
under the support of the National Science Foundation Graduate Research Fellowship (grant no. DGE-1451511). Updated 31 August 2017.