Given the pace of climate change in the Arctic, it is vital to better constrain terrigenous dissolved organic matter (tDOM) fluctuations in large Arctic Rivers and the role that climate change may bring to tDOM inputs into the Arctic Ocean and to the global carbon cycle. This project uses the optical properties of chromophoric dissolved organic matter (CDOM) to investigate the quality, quantity and fate of dissolved organic matter (DOM) in large Arctic Rivers and the interior Arctic Basin. In large rivers surrounding the Arctic, peak discharge CDOM is largely derived from fresh terrestrial plant material whereas during base flow the CDOM pool has a greater microbial imprint, particularly in the Mackenzie. The higher microbial imprint in the Mackenzie can be explained by longer water residence times, which may be important in a warming climate where increased precipitation rates will likely lead to increased hydrological connectivity and therefore longer water residence times. In surface waters of the Canadian Archipelago, 17 % of the DOM pool is of terrestrial origin, even though waters are diluted with sea ice melt, suggesting the likelihood of a subsurface plume of tDOM entrained within river runoff from Arctic Rivers. In the interior Arctic, an elevated terrestrial CDOM signal in the Eurasian Basin (EB) points to the presence of Eurasian river CDOM entrained within river runoff in the Transpolar Drift. In contrast, autochthonous/microbial CDOM sources become more important the Canadian Basin (CB) and the terrestrial CDOM signal is much lower relative to the EB. A good constraint on the nature and distributions of freshwater (FW) in the Arctic Ocean is paramount to understand the role climate change may play for the Arctic’s hydrological cycle. During this study, we used the spatial patterns of terrestrially derived CDOM to better understand the distribution and nature of river runoff across the upper Arctic Basin. This study illustrates the usefulness of CDOM to finger-print water masses within the Arctic Ocean and shows promise to improve our understanding of upper Arctic Ocean ventilation patterns.

Thesis (Ph. D.)--University of Washington, 1973. / Vita. Includes bibliographical references (leaves 155-157).

Abstract This thesis examines the Mid-Pliocene climatic extreme ca. three million years ago (Ma) which was the latest longtime warm period. It is an important topic because the climate back then was warmer compared with the present. The bipolar regions are studied because they represent the largest areas that control the global climate. This study is based on clay mineral research that may significantly improve our knowledge of the Mid-Pliocene climate when combined with other palaeoenvironmental data. The paleoclimatological objectives of this study were: 1) to investigate how clay minerals reflect the Mid-Pliocene Global Warmth event, 2) to study ice sheet development at high latitudes, especially in East-Antarctica, and the history of ice rafting and sea ice, especially in the Arctic Ocean. This thesis deals with the clay mineral distribution and compositional analysis of the Pliocene-aged marine sediment sequences provided by the Ocean Drilling Program (ODP). The first studied site, Site 1165, is located at the continental rise of Prydz Bay, East Antarctica, and the second studied site, Site 911, is located at the Yermak Plateau, north of Svalbard, in the Arctic Ocean. The Pliocene smectite clay minerals at Site 1165 were mainly derived from Antarctic continental sources and transported to the site primarly by bottom currents related to warm events during the last 5 Ma. The evidence obtained in this study shows that the East Antarctic ice sheet may have been a dynamic ice sheet during the past 5 Ma, especially during the Mid-Pliocene. The results from the Mid-Pliocene possibly suggest a general warming trend. Based on the composition of the heavy minerals and clay minerals, at Site 911, the Pliocene smectite clay minerals were mainly transported within sea ice by the Siberian branch of the Transpolar Drift. The results indicate a warming trend at approximately 3 Ma after which they indicate a shift back to glacial conditions. Based on this study, the Mid-Pliocene Global Warmth can be observed in both the Arctic and Antarctic regions.

Tephrochronology is a powerful tool to correlate and improve the chronology of sedimentaryarchives in the Arctic Ocean. The Aniakchak Caldera Forming Eruption (CFE) in Alaska at3.6 cal kyr BP ejected ash that were found in a widespread layer in Alaska, and as cryptotephrain the Chukchi Sea, Newfoundland, and Greenland. This study presents data from the coreSWERUS-L2-4-PC1 (4PC) taken at a water depth of 120 m in the Chukchi Sea. The sharp peakin tephra shards concentration permitted to clearly place the isochron. Unfortunately, the microprobeanalyses were unsuccessful, however measurements of trace elements were performedwith Laser Ablated-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS). The geochemicalsignature of the Aniakchak 3.6 eruption was ensured with significant trace elementratios. The isochron of the eruption combined with the radiocarbon dates from 4PC permittedto calculate the local marine radiocarbon reservoir age offset DR=36446 years. This value isrelatively low compared to recent estimates in the Chukchi Sea, especially to the neighbouringcore SWERUS-L2-2-PC1 were DR=47760. The DR value of this study is explained by theinfluence of the "young" Atlantic water mixing with the "old" Pacific water at the depth wherethe core was taken.

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At ~662 gigatonnes of carbon (GtC), marine dissolved organic matter (DOM) is the largest reduced pool of actively cycling carbon and nitrogen in the oceans1. Operationally defined as smaller than 0.1µm in size, this carbon reservoir comprises all non-living organic matter smaller than a bacterial cell and comprises organic colloids and molecules spanning as a continuum of sizes ranging from marine viruses and large macromolecules (e.g. DNA, enzymes) to small organic molecules (e.g. polymers and monomers)2. With deep apparent 14C-ages ranging between 4900-6400 ybp 3,4, marine DOM is anomalously old given timescales of global ocean ventilation (1000-1500 years). The great age of DOM has remained one of the most elusive lines of scientific inquiry in Chemical Oceanography for decades. The size and molecular composition of DOM has been shown to be a key variable in determining its biological reactivity (e.g. cycling rate) and long-term persistence in the deep ocean5,6. Despite the importance of DOM in the marine carbon and nitrogen cycles, we lack a detailed understanding of the molecular composition of DOM. Due to the high concentration of salts in seawater relative to DOM, it is difficult to analyze the molecular composition of seawater with conventional chemical- or size- fractionation methods without introducing bias (i.e. isolating only hydrophobic and/or high molecular weight DOM). In fact, it is commonly reported that >80% of DOM remains uncharacterized at the molecular level (e.g. not readily identifiable as an individual known biomolecule)5. Nuclear magnetic resonance (NMR) spectroscopy has been used as a tool for several decades to describe the composition of marine DOM isolates7. For example, 13C-NMR of major high molecular weight DOM functional groups at the molecular-level demonstrated that DOM is largely made up of reactive polysaccharides with low aromaticity compared to terrestrial DOM8. To date, all marine DOM NMR measurements have been made on size-fractionated DOM or chemically-fractionated (e.g. solid phase extracted) DOM isolates. In this thesis, I report the first Proton (1H) NMR composition of total seawater DOM from seawater samples collected from 10 stations in Baffin Bay aboard the CCGS Amundsen (2019). Samples were measured using 1H-NMR at uOttawa following a novel water suppression method established by Lam and Simpson9. The use of this method has allowed for the first molecular composition assessment of total seawater DOM to be measured (e.g. without any chemical or size fractionation). I report the % relative abundance of individual biomarkers and determine molar concentrations of two compound classes of interest. These results are shown in Ocean Data View section plots, and are listed within appendix tables, to provide a comprehensive depiction of the changing concentrations of dissolved organic carbon (DOC), total carbohydrates (TCHO), and carboxyl-rich alicyclic molecules (CRAM). In this thesis, I explore changes in the abundance of these unique DOM compound classes and discuss how the composition of DOM directly determines its bioavailability and thus cycling in Baffin Bay 5. The core objective of my thesis was to measure DOM concentrations for TCHO and CRAM, as well as to calculate the production and removal of these key DOM compounds in Baffin Bay due to either physical and/or biological processes. We found that the concentration of both TCHO and CRAM decreased with depth throughout Baffin Bay. This is consistent with previous work suggesting the rapid cycling of carbohydrates, however it contradicts the current paradigm of CRAM cycling. Our results indicate between 21-43% of CRAM produced in the surface is subsequently removed at depth. Rapid cycling of a surface CRAM population suggests that not all CRAM can be considered recalcitrant DOM We live in a time of unprecedented global change. The Arctic Ocean is warming at a rate at least four times faster than the global average10. The impact of a rapidly warming, freshening and increasingly acidified Arctic Ocean on the biogeochemistry of DOM remains unknown. It is imperative that more DOM research be conducted as early as possible in order to better understand these impacts and inform future research directions. The distribution and cycling of CRAM in Baffin Bay provide novel and fundamental knowledge of DOM cycling in a key Arctic region, but could also potentially occur throughout the global ocean. Such data will no doubt be of use in informing future iterations of Earth System Climate models seeking to forecast how the marine carbon cycle will respond to global change.

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Primary marine aerosol particles containing biogenic polymer microgels play a potential role for cloud formation in the pristine high Arctic summer. One of the major sources of the polymer gels in Arctic aerosol was suggested to be the surface water and more specifically, the surface microlayer (SML) of the open leads within the perennial sea ice as a result of bubble bursting at the air-sea interface.  Phytoplankton and/or ice algae are believed to be the main origins of the polymer gels. In this thesis, we examine the chemical composition of biogenic polymers, with focus on polysaccharides, in seawater and airborne aerosol particles collected during the Arctic Summer Cloud Ocean Study (ASCOS) in the summer of 2008. The main results and findings include: A novel method using liquid chromatography coupling with tandem mass spectrometry was developed and applied for identification and quantification of polysaccharides. The enrichment of polysaccharides in the SML was shown to be a common feature of the Arctic open leads. Rising bubbles and surface coagulation of polymers are the likely mechanism for the accumulation of polysaccharides at the SML. The size dependencies of airborne polysaccharides on the travel-time since the last contact with the open sea are indicative of a submicron microgel source within the pack ice.  The similarity of polysaccharides composition observed between the ambient aerosol particles and those generated by in situ bubbling experiments confines the microgel source to the open leads. The demonstrated occurrence of polysaccharides in surface sea waters and in air, with surface-active and hygroscopic properties, has shown their potential to serve as cloud condensation nuclei and subsequently promote cloud-drop activation in the pristine high Arctic. Presumably this possibility may renew interest in the complex but fascinating interactions between marine biology, aerosol, clouds and climate. / At the time of doctoral defence, the following paper was unpublished and had a status as follows: Paper 4: Manuscript

This work aims to increase our understanding of the nature of large scale features of sea ice from a dynamics point of view.Sea ice plays an important part in the exchange of heat and humidity between sea and air and thus is an important component of the climate system. Its physical presence also directly impacts the various forms of life such as diatoms, polar bears and humans alike.The dynamics of sea ice affect both weather and climate, through the large scale drift in the Arctic from the Siberian coast towards Fram Strait, through creation of cracks in the ice called leads or polynyas, and through ridging and other mechanical deformations of ice floes.In this work, we have focused on modelling of ridged ice for a number of reasons. Direct observations of the internal ice state is very difficult to perform and in general, observations of sea ice are either sparse or of limited information density. Ridged ice can be seen as the memory of high ice stress events, giving us a view on these highly dynamic events. Ridging is of major importance for the ice thickness distribution, as the thickest ice can only be formed through mechanical processes. Further, ridged ice is of direct interest for anyone conducting shipping through seasonal or perennial ice covered seas as it can form impenetrable barriers or in extreme even cases crush a ship caught within the ice pack. To this end, a multi-category sea ice model, the HELsinki Multi category Ice model (HELMI), was implemented into the Rossby Centre Ocean model (RCO). HELMI has explicit formulations for ridged and rafted ice, as well as sub-grid scale ice thickness distribution (a feature shared with other multi category models) and an ice strength based on energetics. These features give RCO better representation of sub-grid scale physics and gives us the possibility to study the deformed ice in detail. In paper I we look at the change in behaviour in the Arctic as the ice becomes more mobile, leading to a slight increase in modelled ridged ice volume in the central Arctic, despite a general trend of a decreasing ice cover.Paper II takes us to the Baltic Sea and the possibilities of modelling ridge ice concentration with a statistical model.In Paper III we investigate how the diminishing ice cover in future scenarios affects the biological activity in the Baltic Sea.Finally Paper IV investigates how the ice stress and the internal ice force can be interpreted in terms of ice compression on the ship scale. / <p>At the time of the doctoral defence the following paper was unpublished and had a status as follows: Paper 4: Manuscript</p>