Ocean Heat Content

Upper 200 Meters

But let's start at the top, with a map showing ocean heat trend over the past 30 years in the upper 200 meters (656 feet) of the ocean. Red colors show where warming occurred over these decades. These coincide with areas where destructive hurricanes and cyclones are fueled by warm ocean water.

According to data from the U.S. Environmental Protection Agency, North Atlantic hurricane intensity had "risen noticeably" from 2000 to 2020. ECCO reveals that ocean heat content in upper 200 meters also rose over that time period (magenta line). Moreover, the heat content trend accelerated further after 2017. This latest increase in the ocean heat content trend is an active area of investigation for ECCO researchers.

Upper 700 Meters

Now let's dive deeper with a map showing ocean heat trend over the past 30 years in the upper 700 meters (~2300 feet) of the ocean. Note that some of the areas that are warming in the upper 200 meters depth are cooling at depth.

The time-series graph compares the last 30 years of ocean heat trends between the upper 200 meters and the upper 700 meters. It’s clear that, overall, ocean warming is happening at both depths and has accelerated further over the last five years.

Full Ocean Depth

Now let's get to the bottom of it… ECCO's unique contribution of calculating heat content to the full depth of our ocean. It is clear that our ocean is warming at all depths. Think about it: deeper ocean depths correspond to higher volumes of seawater. Thus, warming in the full depth of the ocean potentially impacts 321,003,271 cubic miles of seawater!

The trend in warming of the full ocean was fairly steady between 1992 and 2017 as shown by the orange line. However, the full ocean heat content trend accelerated sharply from 2017 through the end of this time series, May 2024 (red line). This latest increase in the ocean heat content trend is an active area of investigation for ECCO researchers.

Below is a time-series graph for three levels: Full Depth (black line), 700 meters (blue line) and 200 meters (green line). The overall warming of our ocean's full depth is around 280 ZettaJoules (ZJ). About 60% of this warming is in 0-200 meters and 80% is in 0-700 meters. Thus, about 20% of ocean warming is below 700 meters depth.

The map at bottom shows the long-term ocean heat trends throughout the full depth of our ocean. While patterns are generally similar to ocean heat trends in the upper 200 meters and 700 meters (above), there are some differences. Ocean models with fixed vertical grids, like the MITgcm used by ECCO, generally have too much warming of the deep waters around Antarctica because these models have trouble representing the sinking of dense, cold waters formed on the Antarctic shelf (Antarctic Bottom Water). Thus, users should be aware that ECCO's warming trends in that region may not be realistic, and additional deep measurements are necessary to better constrain the model.