Date of Award

2019-01-01

Degree Name

Master of Science

Department

Geological Sciences

Advisor(s)

Thomas E. Gill

Abstract

The Arctic environment is a dynamic part of Earth’s natural system and is currently undergoing rapid increasing air temperature and decreasing sea ice extent, leading to more open ocean waters. As open water areas become more prevalent, phytoplankton communities near the surface of the ocean can proliferate earlier in the year and are apt to reach higher concentrations by the end of the summer season. Phytoplankton biomass around the world has been known to produce a microscopic biofilm at the surface of the ocean composed of biogenic and biological particles which then become airborne and work as both cloud condensation nuclei and ice nucleating particles. These nuclei can subsequently impact the physical and radiative properties of clouds, thereby affecting the surface energy budget. Various studies have investigated the possible link between phytoplankton biomass and cloud condensation nuclei, but the distinct link between ice nucleating particles and the ocean has only rarely been explored, even more so in the high latitude Arctic environment.

A comprehensive multi-method study was executed to investigate marine aerosols originating from surface of the ocean and their role as ice nucleating particles in Arctic clouds over the Chukchi Sea. The overarching objective was to participate in a field study, in parallel with supporting lab and remote sensing techniques. The field study named Ice Nucleating over the ARCtic (INARCO II) provided excellent research experience for a graduate student to make local in situ measurements of both Arctic air and seawater. This study also explores for the first time how microscopic haloarchaeal species Haloferax sulfurifontis, Natronomonas pharaonsis, Haloquadratum walsbyi, and Halococcus morrhuae perform as ice nucleating particles. All four species have demonstrated some form of ice nucleating ability by nucleating ice at temperatures above homogeneous freezing T≤~-38℃. The third study, remote sensing analysis, quantifiably characterized the Chukchi Sea phytoplankton biomass using satellite derived chlorophyll-a measurements as a tracer for phytoplankton biomass and its correlation to key cloud physical properties including ice cloud effective radius (re), ice water path (IWP), cloud-top height (CTH), cloud-top temperature (CTT), cloud top pressure (CTP), phase, and cloud fraction at varying 1-km or 5-km spatial resolution. Correlation results and scatter plot linear fitting indicate a positive correlation between Chl-a concentrations with ice cloud effective radius (P-value = 0.0013 and R-value = 0.45) and cloud pressure (P = 0.0009, R = 0.46). Negative correlations were found between Chl-a with cirrus cloud reflectance (P = 0.0013, R = -0.45) and ice cloud optical thickness (P = 0.0267, R = -0.32). Spatial analysis results have shown that Chl-a concentrations do not increase evenly in exceptionally high months, but instead increase along the terrestrial coastlines with a weakening gradient leading to near zero concentrations in open ocean. Mean summer Chl-a concentrations for the entire Chukchi Sea showed a variable year to year summer season with a small increasing trend. Additionally, mean summer Chl-a concentrations were maintained between 1.4 mg/m3 and 2.1 mg/m3 in the past 15 years. Together this multi-method investigation produced results exemplifying the importance of considering Arctic plankton biomass and other biogenic INPs in future climatic models since changes in the sea surface concentrations appear to significantly influence certain Arctic cloud properties.

Language

en

Provenance

Received from ProQuest

File Size

86 pages

File Format

application/pdf

Rights Holder

Julio Eduardo Ceniceros

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