Human Impacts on the Hydrosphere

the water cycle in an image

how are precipitation patterns likely to change

• In high latitudes, precipitation is likely to increase

• Likely to decrease over large parts of the subtropics

• Monsoon precipitation is expected to vary in timing and intensity

What has been the trend of extreme precipitation in the Northern Hemisphere since 1950?

• Extreme precipitation intensified in all seasons (1950–2018)

• >70% of the observed trend driven by anthropogenic greenhouse gases

How has extreme precipitation changed in the Southern Hemisphere?

• Changes are regionally and seasonally dependent

extreme arctic 21st centuary projections

• Precipitation increase: 30%-60% by 2100

• Causes:

  1. More open water → increased evaporation

  2. Higher air temperatures → more moisture in the atmosphere

  3. Increased poleward moisture transport

• Shift from snow-dominated to rain-dominated precipitation

How will Asian Monsoon rainfall change as global temperatures rise 2°C–3°C above pre-industrial levels?

Rainfall from individual storms could increase by up to 28%

hotter, wetter, unpredictable

What drives long-term variability in monsoon intensity?

• More intense monsoon winds and rainfall historically follow high atmospheric CO2 and low global ice volume (past 900,000 years)

• Earth’s orbital cycles alone cannot explain monsoon variability

what are direct + indirect impacts of precipitation changes on groundwater

direct: Reduced recharge rates during droughts.

indirect: : Increased groundwater abstraction during droughts.

: How will precipitation changes affect flooding and drinking water?

Increased extreme precipitation leads to more flooding and affects water availability.

How will Arctic precipitation and ice melt affect oceans?

lters snow depth on sea ice → affects ocean stratification, circulation, and primary productivity; accelerated ice sheet melt → 0.28–1.01 m sea level rise by 2100, total melting >60 m; oceanic freshwater could trigger AMOC collapse

How will groundwater recharge in the UK change by 2080?

Recharge will be concentrated into fewer months.

how much fresh warer do healthy ecosystems provide to freshwater resources

75%

since 1970 how much wetland has been lost

35%

what has been the average decline in monitered freshwater wildlife populations between 1970 and 2020

85%

human pertubation to fresh water

firtilisers

how is half the phosphorus availible to crops in argicultural soil

through fertilisers

Impacts of eutrification

Algal blooms result in economic losses of >US$4 billion annually in the US

• Dense mats of floating macrophytes, loss of submerged plants • Deterioration in water taste and odour

Where does most plastic research focus, and how is freshwater treated?

Focus on marine systems; freshwater seen as a pathway to oceans.

How much plastic waste goes directly to oceans, and where is the rest?

~5% of 300+ million tonnes diretly discharged ; remainder stays in terrestrial environments.

global model of plastic waste distrubution

80% of plastic waste is distributed by >1,000 rivers, with most waste carried by small rivers through densely populated urban areas

estimated quantity of plastic entering ocean every year from rivers

1.15-2.41 Mtonnes of plastic

74% between may-october

environmental effects of plastic pollution

• Consumption: direct (mistaken for prey) or indirect (within consumed prey)

• Internal wounding from ingestion of sharp objects

• Blockage of digestive tracts

• Satiation potentially leading to starvation

how does co2 dissolving affect shell-building

• CO₂ from the atmosphere dissolves in seawater.

• CO₂ reacts with water → carbonic acid (H₂CO₃).

• Carbonic acid dissociates → bicarbonate (HCO₃⁻) + hydrogen ions (H⁺).

• Some bicarbonate further dissociates → carbonate ions (CO₃²⁻) + more H⁺.

• More H⁺ lowers pH → ocean acidification.

• Fewer carbonate ions available → harder for marine organisms to make CaCO₃ shells.

How has ocean acidification changed from the late 1800s to projected 2100, and what are the effects on marine life?

Late 1800s:

• Lower atmospheric CO₂ → reduced acidity → higher seawater pH

• Abundant carbonate ions (CO₃²⁻) → healthy corals, mollusks, and marine calcifiers

• 2100 (projected):

• Higher atmospheric CO₂ → increased acidity → lower seawater pH

• More H⁺ (free hydrogen ions), fewer carbonate ions → fewer, smaller marine calcifiers

• Key chemicals: CO₂ → H₂CO₃ (carbonic acid) → HCO₃⁻ (bicarbonate) + H⁺

what is the diff in temp increase per decade in 1980’s compared to now

0.06

0.27

El Niño Southern Oscillation accounts for some of the anomalies but cannot explain them alone

effects of increasing temps on ocean

Coral bleaching • Sea ice formation and persistence • Advantage for invasive species - Japanese sea squirt (Didemnum vexillum) established Holyhead Marina, North Wales, around 2008- 2009 -

more intense atlantic hurricanes

how have atlantic sea surface temps changed

1982 –2020 period has doubled the probability of extremely active tropical cyclone seasons (

recovert of each nutrient for key biogeochemical cycles

Carbon Cycle – ~200,000 years

Phosphorus Cycle – ~20,000 years

Nitrogen Cycle – <10,000 years