science.com.

Lecture 2

Lecture 3: Climate Change & The Oceans

www.solarpowernotes.com

www.skeptical science.com

Nuccitelli et al. (2012).

Stress in the Marine Environment

Stress can be generated by:Temporary fluctuations in conditionsSettlement at edge/outside of appropriate conditionsShifts in climate zonesAdaptations to stressPhenotypic plasticityRapid adaptation through selectionTraditional evolutionary adaptation

10Multiple Stressors in the Marine Environment

PredatorsLight limitationTemperatureCompetition

Stressors brought about by climate changeAlteration of ocean chemistry/Ocean acidificationIncreased seawater temperatureChanges in salinityChanges in currents and sedimentationInvasive speciesLoss of habitatSea-level riseThese stressors can Impact biodiversity, disrupt the plankton cycle, alter the range of species13Alteration of Ocean ChemistryIncreasing accumulation of CO2 in sea leads to ocean acidification

Estimated change in sea water pH caused by human created CO2 between the 1700s and the 1990s, from the Global Ocean Data Analysis Project (GLODAP) and the World Ocean Atlas. Between 1751 and 1994 surface ocean pH is estimated to have decreased from approximately 8.25 to 8.14,[5] representing an increase of almost 30% in H+ ion concentration in the world's oceans. Already ocean pH has decreased by about 30% and if we continue emitting CO2at the same rate by 2100 ocean aciditywill increase by about 150%, a rate that has not been experienced for at least 400,000 years.15

Riebesell et al, Nature, 2000Scanning electron microscopy (SEM) photographs of coccolithophorids underdifferent CO2 concentrations. a, b, d, e, Emiliania huxleyi; and c, f, Gephyrocapsaoceanica collected from cultures incubated at [CO2] < 12 mmol l-1 (ac) and at[CO2] < 3033 mmol l-1 (df), corresponding to pCO2 levels of about 300 p.p.m.v. and780850 p.p.m.v., respectively. Scale bars represent 1mm. Note the difference in thecoccolith structure (including distinct malformations) and in the degree of calcication ofcells grown at normal and elevated CO2 levels. Calcareous marine Coccolithophores. Upper row represents Co2 of 300ppm (slightly above pre-industrial average C02for seawater; i.e. normal seawater), bottom row represents Co2 content of 780-850 ppm. Bars represent 1 micrometer in length16Sea Level Rise

Global sea-level rise is the average increase in the level of the worlds oceans that occurs due to a variety of factors, the most significant being thermal expansion of the oceans and the addition of water by melting of land-based ice sheets, ice caps, and glaciers.Relative sea-level rise refers to the change in sea level relative to the elevation of the adjacent land, which can also subside or rise due to natural and even some human-induced factors which may alter coastal deposition of land based silt. Relative sea-level changes include both global sea-level rise and changes in the vertical elevation of the land surface.The IPCC expresses high confidence that the rate of observed sea level rise increased from the mid 19th to the mid 20th century. During the 20th century, sea level rose at an average rate of 4.8 to 8.8 inches per century (1.2-2.2 mm/year). (IPCC, 2007)Tide gauges show little or no acceleration during the 20th century.Satellite measurements estimate that sea level has been rising at a rate of 9 to 15 inches per century (2.4-3.8 mm/yr) since 1993, more than 50% faster than the rate that tide gauges estimate over the last century.(IPCC, 2007)What affects sea level rise.Thermal expansion: It is estimated that up to half of the sea level rise is attributable to thermal expansion. As the ocean warms, it expands, thus increasing sea level.Ocean temperature continuing to increase. [in 2006 there was data suggesting that the oceans began to cool. It was later found the trend was continuing to warm (view NASA review of the analysis)]Ice melt from Arctic and glacial sources are already contributing to about half of the sea level rise. Antarctica is likely to begin contributing more in the future. But when is not yet strongly known.Recent infrared satellite imagery reveals winter break up of the Wilkins Ice shelf; an unexpected event. This indicates the possibility of acceleration beyond what has been expected up until now.

18

NOAAGlobal Sea Level Rise Simulatorhttp://geology.com/sea-level-rise/

Effects on Intertidal EcosystemsIncreased storms lead to more frequent wave activity

Effects on Intertidal EcosystemsSea level rise would drown some habitats and compact others

Effects on Coral Reefs Increased sea temperatures cause coral bleaching

www.reefteach.com.au

Effects on Coral ReefsReduction in calcification rate due to increased CO2

Death et al, Science, 2008Figure 2: Plot showing the variation of calcification (grams per square centimeter per year) in Porites corals over time. Calcification was regarded as a combination of extension (centimeters per year) and density (grams per cubic centimeter). These data are based on 19002005 data for all colonies. Calcification has declined with 14.2%, from 1.76 g/cm2/y to 1.51 g/cm2/y (modified from Death et al, Science, 2008).28Effects on Seagrass EcosystemsIncreased erosion leads to increased turbidityAlteration of range

Short et al. 2007

Effects on Kelp EcosystemsReduction in range

Effects on Kelp EcosystemsIncreased frequency of El Nino leads to reduction of nutrient supplyIncreases in storms, sedimentation, and turbidity

Impacts to Biodiversity