Identifying Metocean Drivers of Turbidity Using 18 Years of MODIS Satellite Data: Implications for Marine Ecosystems under Climate Change

Paula J Cartwright,Ryan J Lowe,Peter R C S Fearns,Nicola K Browne,Paul Branson,Michael V W Cuttler,Michael O’Leary

doi:10.3390/rs13183616

Abstract

Turbidity impacts the growth and productivity of marine benthic habitats due to light limitation. Daily/monthly synoptic and tidal influences often drive turbidity fluctuations, however, our understanding of what drives turbidity across seasonal/interannual timescales is often limited, thus impeding our ability to forecast climate change impacts to ecologically significant habitats. Here, we analysed long term (18-year) MODIS-aqua data to derive turbidity and the associated meteorological and oceanographic (metocean) processes in an arid tropical embayment (Exmouth Gulf in Western Australia) within the eastern Indian Ocean. We found turbidity was associated with El Niño Southern Oscillation (ENSO) cycles as well as Indian Ocean Dipole (IOD) events. Winds from the adjacent terrestrial region were also associated with turbidity and an upward trend in turbidity was evident in the body of the gulf over the 18 years. Our results identify hydrological processes that could be affected by global climate cycles undergoing change and reveal opportunities for managers to reduce impacts to ecologically important ecosystems.

Highlights

We focus on the potential metocean drivers of turbidity, and the influence of El Niño–Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD)
Lowest mean total suspended matter (TSM) values occurred in deeper water areas located in the NW
The significant coupling of ENSO and IOD to turbidity reveals pathways where climate change could further impact water quality to ecologically critical habitats into the future. This highlights how important a better understanding of the relationship between global climate cycles, regional oceanographic processes and turbidity is to the future management of coastal environmental values under the influence of climate change

Summary

Introduction

The impacts of climate change include ocean warming and acidification [5,6], coastal wind intensification [7], the increasing frequency and severity of extreme weather events [8], changing wave climates [9], and sea level rise [10] which are often strongly coupled to global climate cycles such as El Niño–Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) [11,12,13] While these pressures from climate change often have long-lasting impacts, any co-occurring local declines in water quality, such as increasing water turbidity, can reduce the recovery and resilience of many ecologically critical habitats [14]

Results

Discussion

Conclusion