Sea level rise is probably the most well known impact to oceans from climate change. For those of us who live in low lying coastal areas, it has become the daily dirge we hear from environmental groups, state environmental agencies, and the media: “prepare for inundation by the ocean, prepare for inundation by the ocean.”  Just last week there was yet another public talk in my town about preparing for sea level rise. It may be too late for my town; we get water in the streets every time there is a high tide. Many a time, I’ve had to wear rubber rain boots in order to get to stores and restaurants on the waterfront. It’s kind of like Venice, Italy, where residents keep their rubber boots by the door during “acqua alta.” However our problem is not simply caused by sea level rise from climate change. There are other problems accosting us, like subsidence of the whole area due to what is called isostatic rebound from former glaciers in the area. So we are getting the double whammy. We have seen almost a foot of sea level rise in the last hundred years. How do we know? Well people have been monitoring tide gauges for literally hundreds of years.

Scientists have estimated that global mean sea level has risen by 7.5 inches since 1901. They have based their estimate on records from tide gauges around the world and since 1993 on satellite data. Of course most of the tide gauge records are from Europe and North America. Did you know that the Europeans were installing and measuring tides in the 1700’s? The oldest tide gauge in the United States was installed in San Francisco Bay in 1854. There are long records of tide heights. The problem is sorting all the data so you are not seeing effects of isostatic rebound and other contributors to what scientists term “vertical land motion.” These contributors are well known in areas where there are tide gauges, and the best course of action is not to use data from areas where there is known earth movement causing the land there to rise or subside. Since the late 1990s scientists have installed global positioning receivers (i.e. GPS) near these tide gauges in order to detect the amount of vertical land motion. This will help make the data from the tide gauges useful in the future.

Very precise measurements of sea level rise have been made since the early 1990’s through the use of radar measurements from satellites orbiting the earth. Water in the oceans is constantly moving around as a result of tides, rotation of the earth, general ocean circulation, expansion and contraction from changes in temperature, the whole hydrologic cycle of evaporation, precipitation, and runoff, as well as glacier melting and formation. So sea level varies continuously. To measure the actual change in sea level rise based on the satellite data, scientists have had to build a geodetic reference frame for the earth from which the satellite radar measurements are compared. The reference frame always stays the same even if the water is moving up and down and all around. Since the measurements from the orbiting satellite are so precise, the data can be processed to determine the overall actual sea level rise versus temporary ocean changes.

So is sea level rising consistently? What is its rate of rise? According to the 2013 Intergovernmental Panel on Climate Changes (IPCC) report “The Physical Science Basis” global mean sea level has been rising at rate of .07 of an inch a year since 1901. The number is of course based on both satellite and tide gauge data over the time period. The very precise measurements from satellite data (available since 1993) show a greater rate for global mean sea level rise of .13 of an inch per year – almost double the rise calculated from the combined tide gauge and satellite data.

Sea level has been rising since the end of the last Ice Age about 14,000 years ago. There are many geologists who have made maps of the migration of the world’s coast lines over the last 14,000 years. In fact in the United States, sea level 14,000 years ago was about 300 feet lower than it is today and the coastline was nowhere near where it is now. There is a formula called “Bruns Rule” which gives you the amount of horizontal feet gained or lost per inches of sea level rise. Using the formula, I calculated that the coastline 14,000 years ago was about 5 miles from where it is now. That is a very rough estimate. There are many contributing factors that make the ratios in the Bruns Rule calculation different based on the locality. Mapping by scientists is a better way to determine exactly where the coastline was at the end of the last Ice Age. My calculation is just to give you a feel for how much distance can be covered by a change in sea level.

So what part of sea level rise is just the natural processes going on as a result of the continued interglacial epoch that we live in and what is the amount caused by humans emitting greenhouse gases? The IPCC has calculated the amount of increased heat in the upper ocean caused by human induced climate change since 1971. (See my post on temperature changes in the oceans https://waterblogger.org/general-information/increase-in-ocean-temperatures-climate-change/). Based on their calculations an average of 0.02 inches of sea level change a year has occurred as a result of the warming of the upper ocean (upper 2300 feet). Another .008 inch rise per year is a result of warming from 2300 feet to the bottom of the ocean. So roughly 0.03 inches per year of sea level rise can be attributed to greenhouse gas emissions.

Although the rate of sea level is small on a yearly basis, the rate is steady. It will eventually affect everyone who lives on the coast. And sea level rise is going to be a costly problem. I can see it happening already as my town reconstructs flood walls and puts in new drainage systems to prevent high water from flooding streets, parking lots, an

Whenever I read the latest scientific research on climate, I marvel at how much we don’t know. Meteorology is kind of a Johnny-come-lately sort of science. Sure there are big wheels of climate science like Gilbert Walker who in the 1920’s came up with what is now called the Walker Oscillation. I suspect most people have never heard of the Walker Oscillation, but meteorologists blame El Nino on the reversal of the Walker Oscillation and I’m pretty sure everyone is familiar with El Nino. (Here’s a great link to a blogger at the National Oceanic and Atmospheric Administration who explains the connection between the Walker Oscillation and El Nino:  http://www.climate.gov/news-features/blogs/enso/walker-circulation-ensos-atmospheric-buddy). If you look at other sciences, their foundations are based on centuries of work. Everybody knows of Galileo and Isaac Newton. Chemistry has its Antoine Lavoisier and geology has its Charles Lyell. I suppose you could name a few founding meteorologist from the 19^th century, like Luke Howard. Luke who? Well he gave the names to the cloud formations which we still use today. Remember cumulus, stratus, and cirrus? I’m sure you memorized those names in school at some point. But really the greats of meteorology are probably alive today. The people cited by textbooks in a hundred years as the scientific founders and inventors of modern meteorology are writing papers and publishing now.

Peer review journals are often good at winnowing out papers of questionable scientific merit, but it is even better when you have a board of scientists who are engaged in examining all of the scientific literature on a subject in order to determine its significance; especially when dealing with a global issue like climate change. Or you will end up with a lot of debatable science, like the “hollow earth” theory of the 19^th century touted by such luminaries as John Leslie, who by the way did some of the early work (strangely enough) on heat transfer. Yes there was quite a debate in the early 19^th century on the “hollow earth” theory and it captured the imagination of writers like Jules Verne who in his famous 1864 novel “Journey to the Center of the Earth” sent a German team of explorers down through a volcanic crater into a supposed vast subterranean interior. So a panel of super cautious scientists is what I like to depend on in looking at climate change data. The Intergovernmental Panel on Climate Change (IPCC) sponsored by the United Nations is just such a group. I took the time to read the IPCC report on Climate Change: The Physical Science Basis, which was published by the Cambridge University Press in 2013.

I hope it doesn’t come as a surprise to anyone that heat transfers from the atmosphere to the ocean and vice versa. So as the atmosphere has warmed, so have the oceans. Not by much, you don’t have to worry about burning your toes when walking in the surf. The IPCC estimates there has been about a 0.2 degree Fahrenheit increase per decade in the upper 250 feet of the ocean since 1971. That’s kind of a global average. Temperature increases are variable depending at what latitude and in which ocean you are. And just as heat is transferred from the atmosphere to the ocean, the warmer surface ocean transfers heat to the colder deeper ocean. The IPCC estimates during the same time period, the global average increase in temperature down to 2300 feet has been about 0.03 degrees Fahrenheit per decade.

The IPCC was not confident in using temperature data collected prior to 1971 to make any sort of interpretation of long term ocean temperature changes, because the mix of instruments and the sparcity and variability of sampling didn’t provide consistent enough data to sort out long term temperature changes from the regular variable temperature changes found over seasons, years, decades and centuries. As interest in climate change has increased, so has the extent and quality of temperature measurements in the ocean. The IPCC also reported on the variability in warming among the oceans. Data shows a greater warming in the Northern Hemisphere than elsewhere on the globe.

Climate scientists like to talk about energy inventories, energy storage and energy transfer. Where is all that energy trapped by the greenhouse gases in the atmosphere going? After all, it normally would be reflected back out into space. Now all this heat and energy is trapped in the earth’s atmosphere. These days, there are actually reported inventories of greenhouse gas emissions. So scientists can calculate the total amount of various greenhouse gases, produced in power plants and by other human activities, in the atmosphere on an annual basis.

Climate scientists also can calculate how much energy would be needed to raise the upper ocean temperatures by the 0.14 degrees Fahrenheit the IPCC estimates has occurred over the 40 year period between 1971 and 2010. However methodologies are variable and therefore estimates are variable. I would say, it is a lot of additional energy that must have been transferred to the oceans to raise the temperature in the upper ocean by that much. The IPCC report cites numerous calculations found in the scientific literature. These calculations show an increased heating rate, somewhere between 74 and 137 Terawatts, would have been needed to raise the temperature of the oceans by the amount observed between 1971 and 2010. Most people are familiar with watts. You know if you have a 40 watt or a 60 watt light bulb. The watt is a measurement of energy transfer. A terawatt is one trillion watts. If you turn on your 40 watt bulb in your lamp it is using 40 watts per hour. If you use a 60 watt bulb it is using 60 watts per hour. If you turn on your 137 Terawatt bulb, it is using 137 trillion watts per hour. (Yes I’m just kidding, there are no terawatt bulbs.) But remember this is over 40 years, so the amount of energy transferred to increase the oceans’ temperature to the amount observed would be 137 Terawatts per 40 years.

The IPCC also goes on to calculate the amount of increased energy storage on the Earth between 1971 and 2010 based on annual inventories of greenhouse gas emissions. From the energy storage, they further calculate the resulting increased heating rate for the earth’s total surface and then just for the oceans. Now as far as I’m concerned we’re getting into the realm of science factoid versus science fact with these kinds of calculations. So I’m going to paraphrase what the IPCC states: based on increased energy storage due to greenhouse gas emission, 0.55 watts per square meter of additional heat were applied continuously (24 hours a day, 7 days a week, 365 days a year) over the entire ocean surface between 1971 and 2010.That’s a lot of extra energy going into the oceans of the world.

The ocean is a warmer place. Warmer water has a lot of consequences: changes in ocean chemistry, including oxygen content; impacts on the creatures that live in the oceans; and potential changes in ocean circulation, wind and weather.

I thought I’d catch up on the latest science on how climate change is impacting oceans. What you say? Climate change is impacting oceans? You thought it was just raising air temperature because sunlight can’t escape the atmosphere with all those greenhouse gases clogging up the works? It’s true, climate change is impacting oceans but you don’t hear much about ocean impacts, mostly because people get their news about climate change from the newspapers. It is rare to see a newspaper article on the subject, but it was a newspaper account which prompted my interest in the current science. It was a ham-handed article on the transfer of heat energy to the oceans. The article compared the transfer of heat energy in the atmosphere to the oceans, using the equivalent of how many atomic bombs would need to be detonated in order to produce the same amount of energy.

Every time I see energy measured in nuclear bombs I groan. It’s like every time you hear a politician call another politician Hitler. People are scared of another Hitler, but they are even more scared of nuclear bombs; and with good reason. Nuclear bombs release energy in a single area where they are detonated, which then spreads out to envelope the surrounding area in what we have all seen on television and in movies as a gigantic mushroom cloud of heat and radiation decimating everything within sight. Heat energy being transferred to ocean water is spread out over the oceans, which by the way constitute 70% of the surface of this planet. It goes on everyday of our life. It has gone on every day that the earth has existed with an atmosphere and an ocean. Energy transfer from the atmosphere to the oceans is not the same as a nuclear bomb blast. But people like to use these comparisons I think in order to frighten people.

Anyway the newspaper article covered a recent paper in the journal Nature Climate Change, which was written by scientists from a Department of Energy Laboratory, the National Oceanic and Atmospheric Administration and Pennsylvania State University – an impressive lineup. It’s an interesting article, where these scientists have looked at the heat uptake at various depths in the ocean using measurements taken since 1865. Now most of these measurements are not continuous measurements. Many of them are from what climate scientists like to call transects, where a ship takes various measurements during its voyage. For the journal article, these scientists even used data from the Challenger expedition, an English scientific mission in the 1870s. The Challenger sailed around the world for about six years measuring the depth of the ocean. The folks on the Challenger also measured water temperature. Pretty amazing for those times. These days, there are whole systems of floating buoys in the oceans, measuring all sorts of things. The big system out there, measuring temperature and salinity, is ARGO. I know you thought ARGO was a movie with Ben Affleck. But before it became a movie, it was actually the name of the ship on which Jason sailed in search of the Golden Fleece. (Greek Myth, look it up). So researchers named the current system of scientific instrumentation floats bobbing around out there in all the oceans of the world after a ship used in a futile journey by an ancient mariner; strange choice. The measurement system is huge though and is really cool. The system was set up in 2000 and has about 3000 floating stations. ARGO was devised to complement sea level rise measurements being taken by a satellite, which is named (get this) Jason – those scientists what a funny bunch.

Anyway, the journal article is an analysis of all these various measurements taken over approximately the last 150 years and the results show over half of the steady increase in ocean heat uptake from the atmosphere during this time has occurred since 1997. Well that made me think, wow, I’ve really lost touch with what is going on in climate change research. I’m not a climatologist or an oceanographer, and I tend to keep to issues effecting water on terra firma, but frankly I get a lot of questions on climate change and other than saying to people, it is getting warmer and what don’t you understand about temperature measurements, I do not have a good handle on current research findings. So I am setting out to inform myself and you about the research scientists are conducting on ocean impacts of climate change and what they have been discovering.

There are six big topic areas for how climate change and greenhouse gases are affecting oceans. Of course there is heat uptake as I’ve just been discussing, but there are also temperature increases in the ocean as a result of the heat uptake, there’s sea level rise, there are the changes in salinity, there are the changes to global ocean circulation, and there is ocean acidification. I’m going to check in first with the International Panel on Climate Change. Never heard of them? Well they are the United Nations funded science group who examines current research on climate change. The panel consists of an impressive group of scientists. Their job is to examine current research data for evidence of the extent the earth’s environment is being altered by climate change.

Every few years they produce a report which catalogues research findings to date. Their fifth report came out in 2014. I’m embarrassed to admit, I have only read their first report. It was published in 1990. So I’m only 25 years behind. I look forward to reading the report and providing this blogs readers with an insightful review.