Mooring and Seafloor Pressure End Point Measurements at the Southern Entrance of the Solomon Sea: Subseasonal to Interannual Flow Variability

Abstract

Variability of the flow across the Solomon Sea's southern entrance was examined using end point subsurface moorings and seafloor pressure sensors, reconstructed velocity profiles based on satellite‐derived surface velocity and bottom pressure‐derived subsurface velocity, and 1993–2017 proxy volume transport based on satellite altimetry. The reconstructed velocity correctly represents the fluctuating surface flow and subsurface core providing a high‐frequency continuous observing system for this sea. The mean equatorward volume transport over 0‐ to 500‐m depth layer is 15.2 Sv (1 Sv ≡ 106 m3/s) during July 2012 to May 2017. The measurements resolve the full spectrum of the volume transport including energetic subseasonal variability that fluctuates by as much as 25 Sv over one week. At low‐frequency timescales, the study finds that linear Rossby waves forced by Ekman pumping in the interior of the Pacific influence not only seasonal fluctuations as found by previous studies but also interannual variability. As found previously, the El Niño–Southern Oscillation highly influences interannual volume transport. During the 2015/2016 El Niño, observations show the seasonal cycle to be suppressed from the second half of 2014, prior to the mature phase of the El Niño, to September 2016 along with an increase in across‐transect transport. At subseasonal timescales, local Ekman pumping and remote wind stress curl are responsible for a third of the subseasonal variance. The study highlights the importance of high‐frequency observations at the southern entrance of the Solomon Sea and the ability of a linear Rossby model to represent the low‐frequency variability of the transport.

Moored Observations of Transport in the Solomon Sea

“…() or Anutaliya et al. (), there are statistically significant differences when compared to Davis et al. () and Zilberman et al.…”

“…A potential source of this difference may be the strong interannual variability, on the order of 10 Sv, observed by both Anutaliya et al. () and Kessler et al. () in the Solomon Sea.…”

“…The Solomon Sea mooring deployment-mean total transport is an overestimate when compared to other multiyear estimates (Table 1). While these differences are not statistically significant for the SPICE estimates compared to those of Kessler et al (2019) or Anutaliya et al (2019), there are statistically significant differences when compared to Davis et al (2012) and Zilberman et al (2013). A potential source of this difference may be the strong interannual variability, on the order of Table 3).…”

“…10 Sv, observed by bothAnutaliya et al (2019) andKessler et al (2019) in the Solomon Sea. This strong interannual variability and the different time ranges of the SPICE observations compared toDavis et al (2012) andZilberman et al (2013) may contribute to the difference.…”

“…During the mooring deployment period, repeated glider transects (Davis et al., ; Kessler et al., ) and an array of bottom pressure sensors with dynamic height moorings (Anutaliya et al., ) were deployed in the southern section of the Solomon Sea, independently monitoring transport through the southern opening. The glider observations are the longest source of continuous transport observations in the Solomon Sea, providing quality estimates of seasonal and interannual transport, but their sampling scheme aliases intraseasonal transport variability.…”