An analysis of the strongest tropical storms, known as super typhoons, in the western Pacific over the last half-century reveals that they are intensifying. Higher global temperatures have enhanced global rainfall, particularly over the tropical oceans. Rain that falls on the ocean reduces salinity and allows typhoons to grow stronger.
"This work has identified an extremely important region affected by this, the western tropical Pacific known as Typhoon Alley. These storms are really destructive over that region," said oceanographer Karthik Balaguru of the Department of Energy's Pacific Northwest National Laboratory, who published the work in a recent issue of Nature Communications.
The unique contribution of this work is that it identifies the need to study upper ocean salinity in addition to temperature in examining the intensity of typhoons.
Typhoons — the same storms as their Atlantic cousins known as hurricanes — normally have a natural check on how intense they grow. The storms rely on heat from the ocean to build. Their strong winds whip up the ocean surface. This churns the ocean and brings deeper colder water to the surface, which cools off the surface and reduces the typhoon's power.
Previous studies suggested that as the planet warms, so does the surface of the ocean. As the temperature difference between surface ocean water and deeper water increases, ocean churning by typhoons cools the surface more strongly, which ultimately might decrease the intensity of tropical storms in the future.
But freshwater is less dense than saltwater. A warmer atmosphere brings more rainfall to the ocean than a cooler one. This freshwater collecting on top prevents the churning, keeping the surface warmer. Thus, a lack of ocean water mixing might mean a more intense storm.
Previously, studies that focused on global warming's effect on typhoons did not generally include the salinity factor, so Balaguru and colleagues at PNNL, National Oceanic and Atmospheric Administration and the Massachusetts Institute of Technology decided to incorporate it. This allowed them to look at the effect of freshwater on the ocean both in the past and the future.
They focused on the western Pacific Ocean, where almost a third of tropical storms form. First they looked at the salinity of the top layer of ocean. They saw that between 1958 and 2013, the ocean there did become less salty during typhoon season, and most of this decrease was in the top 50 meters of ocean. A quick overlay of the storms showed that the storm tracks fell along the areas of lower salinity.
To explore further, they looked at how the salinity changes affected the strength of super typhoons, storms that are as strong as category 4 or 5 hurricanes. To do so, they looked at the wakes of cold water the super typhoons left on the ocean as they passed, and how the wakes correlated with salinity. The results showed that in the regions of ocean that were less salty, the storms produced wakes that were not as cold.
The team then analyzed which of the two competing factors — the intensity bump from a decrease in salinity or the intensity snag from a larger ocean temperature gradient — played a bigger role in modulating the intensity of the super typhoons. They found that the influence of salinity was about 50 percent stronger than the ocean temperature effect on the intensity of super typhoons. Super typhoons are most affected by the changes because they rely strongly on ocean's heat as their fuel.
Plugging the relationships into climate model projections for the future, the team found that as greenhouse gases and temperature rise, the increase of rainfall over the oceans will ultimately lead to more intense storms. In addition, the team found this effect using almost 20 different climate models. This consistency gives the researchers confidence in the result.
"Already this effect is intensifying, and it gets worse in the future," said Balaguru. "The reason why this is so significant is that it's happening with the worst storms on the planet. Not only are they intense, but they are very, very big. It's happening in a really important region, to mostly small islands in the Pacific, such as the Philippines, Taiwan and other Oceania Islands. Besides, typhoons also impact many East Asian countries. And there is sea level rise in the background, a double whammy effect on top."
This work was supported by the Department of Energy Office of Science and the National Oceanic and Atmospheric Administration.
Western Indian Ocean Earthquake and Tsun
New Short Film Highlights the Increasing
Wave Energy Project Could Bring Hundreds
Ocean Networks Selects Xtera for the Tu
New Regional Manager for Aquatic Asia Pa
Seatronics Adds Kongsberg Mesotech’s M3
CSA Ocean Sciences Partners with CENTRE
iXBlue expands operations in Brazil, inc
Wild Well Announces Expansion in Asia Pa
TSIC strengthens connectivity in Western
NW Marine Technology Summit Bolsters Mar
Global Buoy Sales Increasing
Pacific NorthWest LNG Installs Metocean
Angola Cables To Host Data Gathering Mee
NCP Consortium and TE SubCom Announce th
New Tools Aiding Storm Prediction, Incre
Sir Eion Edgar Joins Hawaiki Cable to Bu
Coral Bleaching Threat Increasing in Wes
Public Invited to Join NOAA on Deep Sea
New Study from Florida Tech Finds Pacifi
Overfishing and Climate Change, Combined
The Ocean Cleanup Prepares for 2020 Paci
Alcatel-Lucent and Ocean Networks to Ext
The Southwest Pacific Reveals Some of it
Sales and Service Partnership in the Asi
Extreme Pacific Sea Level Events to Doub
Study of Cloud Cover in Tropical Pacific
El Niño Warming Causes Significant Coral
Alcatel-Lucent and Bluesky Pacific Group
Press Release: ECE Offshore and Stema Sy
NASA, University Study Shows Rising Seas
NOAA Explores Protected Areas and Shipwr
El Niño’s Warm Water Devastates Coral Re
Leftover Warm Water in Pacific Ocean Fue
Western Gulf of Mexico Lease Sale Goes L
Jiaolong Submersible Returns with Findin
Bibby HydroMap Completes Western Isles C
Joan Barminski Named New BOEM Pacific Re
The Ocean Cleanup to Share Initial Resul
TSC and OSI Comment on Asia Pacific Netw
The Underwater Centre Awarded for Increa
NOAA’s Okeanos Explorer Journeys into Re
STR Appoints Paul Elliott as General Man
Pacific Basin Completes KVH mini-VSAT Sy
Turnkey Network Development Agreement fo
Docomo Pacific Receives Final Regulatory
AML Oceanographic Appoints New Asia Paci
AccuWeather Predicts an Active East Paci
Southern Cross NEXT Cable Making Pacific
New Key Appointments for Global Maritime
TE SubCom Awarded South Pacific Marine M
Docomo Pacific Starts Marine Lay of ATIS
FSU Researcher Makes Deep-Sea Coral Reef
Ocean Science and Robotics Address Weste
Huawei Marine Hosts 3rd Asia Pacific Sub
Statoil and Partner Further Increasing V
The U.S. Navy Joins 13th Pacific Partner
USNS Brunswick Starts Pacific Partnershi
Great Pacific Garbage Patch Growing Rapi
Recent Study Why Some Hurricanes Rapidly
Keynote Speaker Announced for 2018 CLEAN
U.S. Navy Announces 26th Rim of the Paci
Exercise Rim of the Pacific 2018 Conclud
Ocean Cleanup Projects Begins Trial and
Chevron Australia Extends IMR Contract w
The Long Memory of the Pacific Ocean
Telstra Adds Capacity to Largest Subsea
Wreckage of World War II Aircraft Carrie
UKHO Contracts TCarta to Map Seafloor Ar
US Navy and Allied Nations Participate i
New Asia Pacific Director for i-Tech 7
Study: Humans Are Not Influencing Pacifi
Oceaneering and Pacific Drilling Making
Increasing Global Demand for OSIL Sedime
NOAA to Attend 31st Pacific Islands Foru
SPX FLOW Bolting Systems Increasing Subs
U.S. Pacific Fleet Leads 'Global 11' War
Collaboration to Deliver Aerial Mapping
DSIT Solutions Ltd to Launch its New Swo
U.S., Singapore Navies Strengthen Partne
The Ocean Cleanup Successfully Catches P
James Fisher Subsea Excavation Enjoys Bu
Strong US Presence at Pacific 2019
UK and Australia Use Satellites to Monit
Swire Pacific Offshore Closing Businesse
Increasing Demand for Underwater Motors
Allied Forces Conduct Exercise Pacific V
CSIRO: Seasonal Forecasts Challenged by