Seismic Characterization of Oceanic Water Masses, Water Mass Boundaries, and Mesoscale Eddies SE of New Zealand

Abstract

The Subtropical and Subantarctic Fronts, which separate Subtropical, Subantarctic, and Antarctic Intermediate Waters, are diverted to the south of New Zealand by the submerged continental landmass of Zealandia. In the upper ocean of this region, large volumes of dissolved or suspended material are intermittently transported across the Subtropical Front; however, the mechanisms of such transport processes are enigmatic. Understanding these oceanic boundaries in three dimensions generally depends on measurements collected from stationary vessels and moorings. The details of these data sets, which are critical for understanding how water masses interact and mix at the fine‐scale (<10 m) to mesoscale (10–100 km), are inadequately constrained due to resolution considerations. Southeast of New Zealand, high‐resolution seismic reflection images of oceanic water masses have been produced using petroleum industry data. These seismic sections clearly show three main water masses, the boundary zones (fronts) between them, and associated thermohaline fine structure that may be related to the mixing of water masses in this region. Interpretations of the data suggest that the Subtropical Front in this region is a landward‐dipping zone, with a width that can vary between 20 and 40 km. The boundary zone between Subantarctic Waters and the underlying Antarctic Intermediate Waters is also observed to dip landward. Several isolated lenses have been identified on the three data sets, ranging in size from 9 to 30 km in diameter. These lenses are interpreted to be mesoscale eddies that form at relatively shallow depths along the south side of the Subtropical Front.

Contourite processes associated with the overflow of Pacific Deep Water within the Luzon Trough: Conceptual and regional implications

“…In other areas with more energetic and denser water masses relative to ambient water, seismic reflection data clearly delineate water masses (Yamashita et al, 2011;Gorman et al, 2018).…”

Pencitraan Thermohaline Fine Structure Menggunakan Seismik Refleksi Multikanal Di Laut Maluku

“…Kontras salinitas pada kedalaman 400 m dan 800 m diduga sebagai batas massa air memiliki karakteristik suhu dan salinitas yang berbeda. Gorman et al (2018) menyatakan bahwa salah satu penyebab refleksi di kolom perairan adalah adanya batas massa air yang memiliki suhu dan salinitas yang berbeda. Hal ini sejalan dengan penelitian Rahma et al (2020) mengungkap bahwa terdapat kontribusi massa air North Pacific Intermediate Water (NPIW), North Pacific Shallow Water (NPSW), serta South Pacific Subtropical Lower Thermocline Water (SPSLTW) pada kedalaman 200-500 m di Laut Maluku.…”

Investigating Eddies From Coincident Seismic and Hydrographic Measurements in the Chukchi Borderlands, the Western Arctic Ocean

“…Seismic oceanography has been successfully used to image a variety of oceanic features, for example, oceanic fronts (Gunn et al., 2020; Holbrook et al., 2003; Nakamura et al., 2006), water mass boundaries (Gorman et al., 2018; Gunn et al., 2018), mesoscale eddies (Biescas et al., 2008; Gunn et al., 2018; Pinheiro et al., 2010; Tang et al., 2014), internal solitary waves (Bai et al., 2017; Fan et al., 2021), and thermohaline staircases (Biescas et al., 2010; Buffet et al., 2017; Fer et al., 2010). Here, we present seismic reflection sections of the water column produced from multichannel seismic reflection (MCS) data acquired in late summer 2011 across the Chukchi Borderlands (Figure 1).…”