Marine Atlas: Maximizing Benefits for Solomon Islands

Normal conditions

El Niño conditions

Westerly Winds

Strong Trade Winds

Weaker Trade Winds

Both kinds of currents—the thermohaline ones in the deep water and the wind-driven one on the surface—are very important to Solomon Islands. On their journey, water masses transport two things around the globe and through Solomon Islands’ wa- ters. Firstly, matter such as solids, dissolved substances and gases are carried by the currents, including salt, larvae (see also chapter “Travellers or homebodies”), plastics and oil (see also chapters “Plastic oceans” and “Full speed ahead”). Secondly, currents transport energy in the form of heat. Cur- rents therefore have a significant impact on the global climate. El Niño is an example of the big impact that regional climate variability related to ocean currents has on Solomon Islands (see graphs and chapter “Hotter and higher”). Normally, strong trade winds blow from east to west across the Pacific Ocean around the equator. As the winds push warm surface water from South America west towards Asia and Australia, cold water wells up from below in the east to take its place along the west coast of South Amer- ica. This creates a temperature disparity across the Pacific, which also keeps the trade winds blowing. The accumulation of warm water in the west heats the air, caus- ing it to rise and create unstable weather, making the western Pacific region warm and rainy. Cool, drier air is usually found on the eastern side of the Pacific. In an El Niño year, the trade winds weak- en or break down. The warm water that is normally pushed towards the western Pacific washes back across, piling up on the east side of the Pacific from California to Chile, causing rain and storms and in- creasing the risk of cyclone formation over the tropical Pacific Ocean (Climate Predic- tion Center, 2005).

Water Heated by the Sun

Strong Upwelling

Weak Upwelling

WarmWater

WarmWater

Thermocline

Thermocline

Deep Cold Water

Deep Cold Water

120°E

140°E

160°E

180°

160°W

140°W

120°W

100°W

80°W

120°E

140°E

160°E

180°

160°W

140°W

120°W

100°W

80°W

Darwin, Australia

Lima, Peru

Solomon Islands

Darwin, Australia

Solomon Islands

Lima, Peru

On the other side, the western Pacific experiences particularly dry conditions. The periods 1997–1998 and 2014–2016 were among the strongest events on record. For example, in 2015, both Papua New Guinea and Solomon Islands experienced unusually dry and cold conditions, resulting in water shortages and frosts, which wiped out many food crops. Moreover, El Niño contributes to an increase in global temperatures. In the particularly hot year of 2015, El Niño was responsible for about 10 per cent of the temperature rise. In turn, rising global and ocean temperatures may intensify El Niño (Cai et al., 2014). In summary, sea currents driven by wind, heat and salinity influence not only Solomon Islands’ marine biodiversity, but also its rain- fall patterns and temperature on land.

Solomon Islands Provisional EEZ Boundary

SEA SURFACE CURRENTS Direction and velocity (m/s)

50

100

200 km

0.13

0.10

5°S

Sources : Becker et al, 2009; Claus et al, 2016; ESR, 2009; Smith and Sandwell, 1997. Copyright © MACBIO Map produced by GRID-Arendal

0.05

0.03

10°S

15°S

160°E

155°E

165°E

170°E

MAXIMIZING BENEFITS FOR SOLOMON ISLANDS

SUPPORTING VALUES

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