Typhoon Rammasun-Induced Near-Inertial Oscillations Observed in the Tropical Northwestern Pacific Ocean

Wind-induced near-inertial oscillations (NIOs) have been known to propagate their energy downward and equatorward, yet few observations have confirmed this in tropical regions. Using measurements from a moored ADCP in the tropical northwestern Pacific, we report an energetic NIO event associated with Typhoon Rammasun in May 2008, when an anti-cyclonic warm eddy existed around the mooring site. Our analyses reveal that the anti-cyclonic eddy traps the NIO energy at two layers around 120 and 210 m where the buoyancy frequency show high values. The NIO energy continuously decays at layers below its maximum at 210 m, and disappears at depths below the thermocline. During their propagation from 137 to 649 stretched-meter depths (equivalent to 100 - 430 m), NIOs shift their frequencies from 0.92f to 1.05f probably due to the effective f, which changes its magnitude from smaller to larger than local inertial frequency f in the anti-cyclonic eddy. In addition, their vertical energy propagation becomes faster from 0.17 to 0.64 mm s-1. Decomposition of downward and upward NIO energy propagation shows that the typhoon-induced NIOs remain 29% of their energy in the upper layer, and transfer 71% to the subsurface layers. Our results suggest that typhoon-induced NIOs interacting with meso-scale eddies can play an important role in providing the energy source available for ocean mixing in the tropical regions

Sea level rise and coastal erosion in the Hawaiian Islands

Thesis (Ph. D.)--University of Hawaii at Manoa, 1995.Includes bibliographical references (leaves 181-188).Microfiche.xvii, 188 leaves, bound ill. 29 cmTime series and the power spectral distributions of relative sea levels are analyzed at selected tide-gauge stations in the western and central North Pacific between equator and about 30°N, in association with different time scales of motions. Coastal response to these sea-level dynamics is discussed in detail, based on the aerial photographs of shoreline changes. Wave climate around the Hawaiian Islands as well as surf conditions on Oahu are examined for simulating cross-shore beach erosion processes with an energetics-based sediment transport model. Long-term trend of relative sea-level rise during the past several decades (+1 to +5 cm/decade at most of the tide-gauge stations) is primarily affected by the local tectonism such as volcanic loading, plate movement and reef evolution, and subduction at the plate boundaries. Continual volcanic loading at Kilauea, Hawaii results in consequential subsidence of the Hawaiian Islands. Secondary reason for sea-level rise is the thermal expansion of sea surface waters due to global warming by increasing greenhouse gases, which may be potentially more significant in the near future. Interannual sea-level fluctuations, associated with ENSO (El Nino Southern Oscillation) phenomena, seem to be the primary factor to cause serious beach erosion (up to 10 times the long-term trend). Mean annual cycle of sea level (H ≈ 10 cm) and alternate annual wave conditions are the main causes of the cross-shore oscillation of sediment transport, although there is still some loss of sediments to deep-water region. Short-term change of beach profiles is basically caused by incoming wave conditions as well as sea-level height, sediment characteristics, and underlying geology. Simulations by a cross-shore sediment transport model show that higher waves result in faster offshore transport and deeper depth of active profile change, and that beach recovery process is usually much slower than the erosion process, especially after a storm surge. Deep erosion during a storm surge can not be recovered for much longer duration by mild post-storm waves, but may be partly recovered by non-breaking long waves such as longer-period swells

Moored Buoy System in the western Pacific

http://www.godac.jamstec.go.jp/darwin/cruise/mirai/mr10-07/

DataSheet_1_Destination of New Guinea Coastal Undercurrent in the western tropical Pacific: Variability and linkages.pdf

The New Guinea Coastal Undercurrent (NGCUC) is considered a bottleneck in the western tropical Pacific (WTP), carrying upper-to-intermediate waters from the south to the northwestern Pacific, thereby playing a fundamental role in the interhemispheric water mass exchange. However, how the NGCUC links to the circulation in the WTP was insufficiently studied. This work explores the destination of NGCUC waters, its spatiotemporal changes, and possible physical processes linked with the downstream NGCUC using ocean reanalysis for 22 years (1994 – 2015). Lagrangian particle tracking discloses eight major destinations of the NGCUC: The Equatorial Undercurrent (EUC, 35.26%), the North Equatorial Countercurrent (NECC, 12.3%), the North (13.33%) and South (8.85%) Subsurface Countercurrents, the Equatorial Deep Jet (11.49%), the Mindanao Undercurrent (13.24%), and the Indonesian (3.47%) and Halmahera (0.86%) Throughflows. The NGCUC waters are distributed mainly to the east (81.65%) and their dissemination varies markedly with depth. These destinations exhibit significant variations on seasonal and interannual time scales. The NGCUC strengthens (weakens) during summer (winter) and more NGCUC waters are distributed westward and northeastward (eastward). Interannually, the distribution of the NGCUC water is influenced by El Niño-Southern Oscillation, in which most of its eastward-distributed waters shift northward (equatorward) in El Niño (La Niña) phase joining the strengthened NECC (EUC). Changes in the NGCUC water destination can transform the water mass properties in the WTP. The findings of this study also emphasize the fundamental role of eddies in trapping and redistributing the NGCUC waters and linking the currents in the WTP.</p

Primers used in the pyrosequencing of <i>dddP</i> genes.

<p>*Specific oligonucleotides consist of a degenerate ‘core’ (plain text) and non-degenerate ‘clamp’ (bold) region.</p><p>Primers used in the pyrosequencing of <i>dddP</i> genes.</p

Pyrosequencing Revealed SAR116 Clade as Dominant <i>dddP</i>-Containing Bacteria in Oligotrophic NW Pacific Ocean

<div><p>Dimethyl sulfide (DMS) is a climatically active gas released into the atmosphere from oceans. It is produced mainly by bacterial enzymatic cleavage of dimethylsulfoniopropionate (DMSP), and six DMSP lyases have been identified to date. To determine the biogeographical distribution of bacteria relevant to DMS production, we investigated the diversity of dddP—the most abundant DMS-producing gene—in the northwestern Pacific Ocean using newly developed primers and the pyrosequencing method. Consistent with previous studies, the major dddP-containing bacteria in coastal areas were those belonging to the Roseobacter clade. However, genotypes closely related to the SAR116 group were found to represent a large portion of dddP-containing bacteria in the surface waters of the oligotrophic ocean. The addition of DMSP to a culture of the SAR116 strain Candidatus Puniceispirillum marinum IMCC1322 resulted in the production of DMS and upregulated expression of the dddP gene. Considering the large area of oligotrophic water and the wide distribution of the SAR116 group in oceans worldwide, we propose that these bacteria may play an important role in oceanic DMS production and biogeochemical sulfur cycles, especially via bacteria-mediated DMSP degradation.</p></div

Tree showing the phylogentic relationships of representative amino acid sequences of each OTU obtained in this study (red text).

<p>Only OTUs constituting more than 10% of at least one sample are shown. The text in parentheses after bacterial names represent the locus tag for each genome in the IMG/ER database. The percentage in parentheses after OTU names represent maximum percentage of each OTU found in samples. Group names according to Todd <i>et al</i>. (2009) are shown on the right. A phylogentic tree for all OTUs can be found in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0116271#pone.0116271.s004" target="_blank">S2 Fig.</a> Only bootstrap values >60% are shown at the nodes.</p

Contour plots showing the percentage of each major OTU as a proportion of all sequences.

<p>Black dots represent sampling depths.</p

Map of sampling stations in the NW Pacific Ocean.

<p>The base map is a composite image of sea surface temperature from 1 to 5 June 2010, obtained from SeaWiFS.</p

DMS production and expression of <i>dddP</i> mRNA of <i>Candidatus</i> Puniceispirillum marinum.

<p>(A) Closed circles represent cells grown in R2A broth supplemented with 500 μM of DMSP. Open circles and triangles represent controls without cells and without DMSP, respectively. (B) RT-PCR of <i>dddP</i> mRNA and 16S rRNA of cells grown in media with DMSP and without DMSP, respectively.</p