Hydrospheric Problems of Climate Change

The Oceans are Warming

(click image to enlarge)
Changes in Ocean Heat Content Anomaly 1955-2017
Source: NOAA Climate.gov:Ocean Heat Content

The above chart shows the annual changes in ocean heat content from 1955 to 2017, using as a baseline the average ocean heat content from 1955-2006. The measurements apply to the top 700 meters of the ocean. Obviously, the heat content of the oceans is increasing, with a steady increase starting around 1990.


Over 90% of the Earth's warming over the last 50 years has occurred in the oceans. The top 700 meters of the ocean accounts for about 63% of warming of the Earth, with the lower layers of the oceans absorbing about 30%. This has saved the Earth's atmosphere from the destructively intense warming that would have taken place due to the use of fossil fuels if global warming had taken place exclusively in the atmosphere.

Oceans are Rising

(click image to enlarge)
Source: GlobalChange.gov Global Sea Level Rise

Global sea level has risen about 8 inches since the 1880's. The rate of sea level rise has also increased and is now more than one inch per decade. This makes rising global sea level a major, challenging aspect of climate change.


There are two factors driving the rise in sea level:

  • Thermal expansion of the oceans, as their heat content increases
  • Addition of water to the oceans due to melting of ice on land and sea


The perils associated with sea level rise are primarily felt by inhabitants of the shoreline areas in all parts of the Earth. Both human settlements and animal/plant ecosystems are disrupted by the encroachment of rising ocean levels on the areas where they live.

The Oceans are More Acidic

(click image to enlarge)
Ocean Acidification
Source: NOAA PMEL Carbon Program

When fossil fuels are burned carbon dioxide(CO2) is released into the atmosphere. That CO2 is then absorbed to a large extent by the oceans. It is estimated that the oceans absorb about 25% of the CO2 released into the atmosphere. Once in the ocean, that CO2 undergoes chemical reactions that result in the formation of carbonic acid. This causes the oceans to become more acidic. Increased acidity can have multifarious, negative effects on the biota occupying the seas.

Lowering of Ocean Oxygen

Ocean oxygen levels are declining in over 500 sites around the world. The causes of oceanic deoxygenation are:

  • increasing ocean temperatures due to global warming from climate change
  • excess nutrients added to oceans in the form of waste from human activities